Merge pull request #26 from FenrirWolf/thread

Initial thread support

ctr-std/Cargo.toml

@@ -14,6 +14,3 @@ path = "../ctru-sys"
 
 [dependencies.alloc_system]
 version = "0.1.1"
-
-[dependencies.spin]
-version = "0.4"

ctr-std/src/io/mod.rs

@@ -256,7 +256,7 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use cmp;
-use std_unicode::str as core_str;
+use core::str as core_str;
 use error as std_error;
 use fmt;
 use result;

ctr-std/src/lib.rs

@@ -1,6 +1,7 @@
 #![feature(alloc)]
 #![feature(allow_internal_unstable)]
 #![feature(box_syntax)]
+#![feature(cfg_target_has_atomic)]
 #![feature(cfg_target_thread_local)]
 #![feature(collections)]
 #![feature(collections_bound)]
@@ -11,23 +12,30 @@
 #![feature(char_escape_debug)]
 #![feature(dropck_eyepatch)]
 #![feature(float_extras)]
+#![feature(fn_traits)]
 #![feature(fnbox)]
 #![feature(fused)]
 #![feature(generic_param_attrs)]
 #![feature(int_error_internals)]
+#![feature(integer_atomics)]
 #![feature(lang_items)]
 #![feature(macro_reexport)]
 #![feature(oom)]
+#![feature(on_unimplemented)]
 #![feature(optin_builtin_traits)]
 #![feature(prelude_import)]
 #![feature(raw)]
+#![feature(shared)]
 #![feature(slice_concat_ext)]
 #![feature(slice_patterns)]
 #![feature(staged_api)]
 #![feature(str_internals)]
 #![feature(thread_local)]
 #![feature(try_from)]
+#![feature(unboxed_closures)]
 #![feature(unicode)]
+#![feature(unique)]
+#![feature(untagged_unions)]
 #![feature(zero_one)]
 #![allow(non_camel_case_types, dead_code, unused_features)]
 #![no_std]
@@ -57,9 +65,6 @@ extern crate compiler_builtins;
 extern crate ctr_libc as libc;
 extern crate ctru_sys as libctru;
 
-// stealing spin's mutex implementation for now
-extern crate spin;
-
 // The standard macros that are not built-in to the compiler.
 #[macro_use]
 mod macros;
@@ -151,6 +156,7 @@ pub mod ffi;
 pub mod io;
 pub mod num;
 pub mod os;
+pub mod panic;
 pub mod path;
 pub mod sync;
 pub mod time;

ctr-std/src/panic.rs

@@ -0,0 +1,394 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Panic support in the standard library
+
+#![stable(feature = "std_panic", since = "1.9.0")]
+
+use any::Any;
+use cell::UnsafeCell;
+use fmt;
+use ops::{Deref, DerefMut};
+use panicking;
+use ptr::{Unique, Shared};
+use rc::Rc;
+use sync::{Arc, Mutex, RwLock, atomic};
+use thread::Result;
+
+//#[stable(feature = "panic_hooks", since = "1.10.0")]
+//pub use panicking::{take_hook, set_hook, PanicInfo, Location};
+
+/// A marker trait which represents "panic safe" types in Rust.
+///
+/// This trait is implemented by default for many types and behaves similarly in
+/// terms of inference of implementation to the `Send` and `Sync` traits. The
+/// purpose of this trait is to encode what types are safe to cross a `catch_unwind`
+/// boundary with no fear of unwind safety.
+///
+/// ## What is unwind safety?
+///
+/// In Rust a function can "return" early if it either panics or calls a
+/// function which transitively panics. This sort of control flow is not always
+/// anticipated, and has the possibility of causing subtle bugs through a
+/// combination of two cricial components:
+///
+/// 1. A data structure is in a temporarily invalid state when the thread
+///    panics.
+/// 2. This broken invariant is then later observed.
+///
+/// Typically in Rust, it is difficult to perform step (2) because catching a
+/// panic involves either spawning a thread (which in turns makes it difficult
+/// to later witness broken invariants) or using the `catch_unwind` function in this
+/// module. Additionally, even if an invariant is witnessed, it typically isn't a
+/// problem in Rust because there are no uninitialized values (like in C or C++).
+///
+/// It is possible, however, for **logical** invariants to be broken in Rust,
+/// which can end up causing behavioral bugs. Another key aspect of unwind safety
+/// in Rust is that, in the absence of `unsafe` code, a panic cannot lead to
+/// memory unsafety.
+///
+/// That was a bit of a whirlwind tour of unwind safety, but for more information
+/// about unwind safety and how it applies to Rust, see an [associated RFC][rfc].
+///
+/// [rfc]: https://github.com/rust-lang/rfcs/blob/master/text/1236-stabilize-catch-panic.md
+///
+/// ## What is `UnwindSafe`?
+///
+/// Now that we've got an idea of what unwind safety is in Rust, it's also
+/// important to understand what this trait represents. As mentioned above, one
+/// way to witness broken invariants is through the `catch_unwind` function in this
+/// module as it allows catching a panic and then re-using the environment of
+/// the closure.
+///
+/// Simply put, a type `T` implements `UnwindSafe` if it cannot easily allow
+/// witnessing a broken invariant through the use of `catch_unwind` (catching a
+/// panic). This trait is a marker trait, so it is automatically implemented for
+/// many types, and it is also structurally composed (e.g. a struct is unwind
+/// safe if all of its components are unwind safe).
+///
+/// Note, however, that this is not an unsafe trait, so there is not a succinct
+/// contract that this trait is providing. Instead it is intended as more of a
+/// "speed bump" to alert users of `catch_unwind` that broken invariants may be
+/// witnessed and may need to be accounted for.
+///
+/// ## Who implements `UnwindSafe`?
+///
+/// Types such as `&mut T` and `&RefCell<T>` are examples which are **not**
+/// unwind safe. The general idea is that any mutable state which can be shared
+/// across `catch_unwind` is not unwind safe by default. This is because it is very
+/// easy to witness a broken invariant outside of `catch_unwind` as the data is
+/// simply accessed as usual.
+///
+/// Types like `&Mutex<T>`, however, are unwind safe because they implement
+/// poisoning by default. They still allow witnessing a broken invariant, but
+/// they already provide their own "speed bumps" to do so.
+///
+/// ## When should `UnwindSafe` be used?
+///
+/// Is not intended that most types or functions need to worry about this trait.
+/// It is only used as a bound on the `catch_unwind` function and as mentioned above,
+/// the lack of `unsafe` means it is mostly an advisory. The `AssertUnwindSafe`
+/// wrapper struct in this module can be used to force this trait to be
+/// implemented for any closed over variables passed to the `catch_unwind` function
+/// (more on this below).
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+#[rustc_on_unimplemented = "the type {Self} may not be safely transferred \
+                            across an unwind boundary"]
+pub trait UnwindSafe {}
+
+/// A marker trait representing types where a shared reference is considered
+/// unwind safe.
+///
+/// This trait is namely not implemented by `UnsafeCell`, the root of all
+/// interior mutability.
+///
+/// This is a "helper marker trait" used to provide impl blocks for the
+/// `UnwindSafe` trait, for more information see that documentation.
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+#[rustc_on_unimplemented = "the type {Self} contains interior mutability \
+                            and a reference may not be safely transferrable \
+                            across a catch_unwind boundary"]
+pub trait RefUnwindSafe {}
+
+/// A simple wrapper around a type to assert that it is unwind safe.
+///
+/// When using `catch_unwind` it may be the case that some of the closed over
+/// variables are not unwind safe. For example if `&mut T` is captured the
+/// compiler will generate a warning indicating that it is not unwind safe. It
+/// may not be the case, however, that this is actually a problem due to the
+/// specific usage of `catch_unwind` if unwind safety is specifically taken into
+/// account. This wrapper struct is useful for a quick and lightweight
+/// annotation that a variable is indeed unwind safe.
+///
+/// # Examples
+///
+/// One way to use `AssertUnwindSafe` is to assert that the entire closure
+/// itself is unwind safe, bypassing all checks for all variables:
+///
+/// ```
+/// use std::panic::{self, AssertUnwindSafe};
+///
+/// let mut variable = 4;
+///
+/// // This code will not compile because the closure captures `&mut variable`
+/// // which is not considered unwind safe by default.
+///
+/// // panic::catch_unwind(|| {
+/// //     variable += 3;
+/// // });
+///
+/// // This, however, will compile due to the `AssertUnwindSafe` wrapper
+/// let result = panic::catch_unwind(AssertUnwindSafe(|| {
+///     variable += 3;
+/// }));
+/// // ...
+/// ```
+///
+/// Wrapping the entire closure amounts to a blanket assertion that all captured
+/// variables are unwind safe. This has the downside that if new captures are
+/// added in the future, they will also be considered unwind safe. Therefore,
+/// you may prefer to just wrap individual captures, as shown below. This is
+/// more annotation, but it ensures that if a new capture is added which is not
+/// unwind safe, you will get a compilation error at that time, which will
+/// allow you to consider whether that new capture in fact represent a bug or
+/// not.
+///
+/// ```
+/// use std::panic::{self, AssertUnwindSafe};
+///
+/// let mut variable = 4;
+/// let other_capture = 3;
+///
+/// let result = {
+///     let mut wrapper = AssertUnwindSafe(&mut variable);
+///     panic::catch_unwind(move || {
+///         **wrapper += other_capture;
+///     })
+/// };
+/// // ...
+/// ```
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+pub struct AssertUnwindSafe<T>(
+    #[stable(feature = "catch_unwind", since = "1.9.0")]
+    pub T
+);
+
+// Implementations of the `UnwindSafe` trait:
+//
+// * By default everything is unwind safe
+// * pointers T contains mutability of some form are not unwind safe
+// * Unique, an owning pointer, lifts an implementation
+// * Types like Mutex/RwLock which are explicilty poisoned are unwind safe
+// * Our custom AssertUnwindSafe wrapper is indeed unwind safe
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl UnwindSafe for .. {}
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<'a, T: ?Sized> !UnwindSafe for &'a mut T {}
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<'a, T: RefUnwindSafe + ?Sized> UnwindSafe for &'a T {}
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<T: RefUnwindSafe + ?Sized> UnwindSafe for *const T {}
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<T: RefUnwindSafe + ?Sized> UnwindSafe for *mut T {}
+#[unstable(feature = "unique", issue = "27730")]
+impl<T: UnwindSafe + ?Sized> UnwindSafe for Unique<T> {}
+#[unstable(feature = "shared", issue = "27730")]
+impl<T: RefUnwindSafe + ?Sized> UnwindSafe for Shared<T> {}
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<T: ?Sized> UnwindSafe for Mutex<T> {}
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<T: ?Sized> UnwindSafe for RwLock<T> {}
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<T> UnwindSafe for AssertUnwindSafe<T> {}
+
+// not covered via the Shared impl above b/c the inner contents use
+// Cell/AtomicUsize, but the usage here is unwind safe so we can lift the
+// impl up one level to Arc/Rc itself
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<T: RefUnwindSafe + ?Sized> UnwindSafe for Rc<T> {}
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<T: RefUnwindSafe + ?Sized> UnwindSafe for Arc<T> {}
+
+// Pretty simple implementations for the `RefUnwindSafe` marker trait,
+// basically just saying that this is a marker trait and `UnsafeCell` is the
+// only thing which doesn't implement it (which then transitively applies to
+// everything else).
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl RefUnwindSafe for .. {}
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<T: ?Sized> !RefUnwindSafe for UnsafeCell<T> {}
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<T> RefUnwindSafe for AssertUnwindSafe<T> {}
+
+#[stable(feature = "unwind_safe_lock_refs", since = "1.12.0")]
+impl<T: ?Sized> RefUnwindSafe for Mutex<T> {}
+#[stable(feature = "unwind_safe_lock_refs", since = "1.12.0")]
+impl<T: ?Sized> RefUnwindSafe for RwLock<T> {}
+
+#[cfg(target_has_atomic = "ptr")]
+#[stable(feature = "unwind_safe_atomic_refs", since = "1.14.0")]
+impl RefUnwindSafe for atomic::AtomicIsize {}
+#[cfg(target_has_atomic = "8")]
+#[unstable(feature = "integer_atomics", issue = "32976")]
+impl RefUnwindSafe for atomic::AtomicI8 {}
+#[cfg(target_has_atomic = "16")]
+#[unstable(feature = "integer_atomics", issue = "32976")]
+impl RefUnwindSafe for atomic::AtomicI16 {}
+#[cfg(target_has_atomic = "32")]
+#[unstable(feature = "integer_atomics", issue = "32976")]
+impl RefUnwindSafe for atomic::AtomicI32 {}
+#[cfg(target_has_atomic = "64")]
+#[unstable(feature = "integer_atomics", issue = "32976")]
+impl RefUnwindSafe for atomic::AtomicI64 {}
+
+#[cfg(target_has_atomic = "ptr")]
+#[stable(feature = "unwind_safe_atomic_refs", since = "1.14.0")]
+impl RefUnwindSafe for atomic::AtomicUsize {}
+#[cfg(target_has_atomic = "8")]
+#[unstable(feature = "integer_atomics", issue = "32976")]
+impl RefUnwindSafe for atomic::AtomicU8 {}
+#[cfg(target_has_atomic = "16")]
+#[unstable(feature = "integer_atomics", issue = "32976")]
+impl RefUnwindSafe for atomic::AtomicU16 {}
+#[cfg(target_has_atomic = "32")]
+#[unstable(feature = "integer_atomics", issue = "32976")]
+impl RefUnwindSafe for atomic::AtomicU32 {}
+#[cfg(target_has_atomic = "64")]
+#[unstable(feature = "integer_atomics", issue = "32976")]
+impl RefUnwindSafe for atomic::AtomicU64 {}
+
+#[cfg(target_has_atomic = "8")]
+#[stable(feature = "unwind_safe_atomic_refs", since = "1.14.0")]
+impl RefUnwindSafe for atomic::AtomicBool {}
+
+#[cfg(target_has_atomic = "ptr")]
+#[stable(feature = "unwind_safe_atomic_refs", since = "1.14.0")]
+impl<T> RefUnwindSafe for atomic::AtomicPtr<T> {}
+
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<T> Deref for AssertUnwindSafe<T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        &self.0
+    }
+}
+
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<T> DerefMut for AssertUnwindSafe<T> {
+    fn deref_mut(&mut self) -> &mut T {
+        &mut self.0
+    }
+}
+
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+impl<R, F: FnOnce() -> R> FnOnce<()> for AssertUnwindSafe<F> {
+    type Output = R;
+
+    extern "rust-call" fn call_once(self, _args: ()) -> R {
+        (self.0)()
+    }
+}
+
+#[stable(feature = "std_debug", since = "1.16.0")]
+impl<T: fmt::Debug> fmt::Debug for AssertUnwindSafe<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("AssertUnwindSafe")
+            .field(&self.0)
+            .finish()
+    }
+}
+
+/// Invokes a closure, capturing the cause of an unwinding panic if one occurs.
+///
+/// This function will return `Ok` with the closure's result if the closure
+/// does not panic, and will return `Err(cause)` if the closure panics. The
+/// `cause` returned is the object with which panic was originally invoked.
+///
+/// It is currently undefined behavior to unwind from Rust code into foreign
+/// code, so this function is particularly useful when Rust is called from
+/// another language (normally C). This can run arbitrary Rust code, capturing a
+/// panic and allowing a graceful handling of the error.
+///
+/// It is **not** recommended to use this function for a general try/catch
+/// mechanism. The `Result` type is more appropriate to use for functions that
+/// can fail on a regular basis. Additionally, this function is not guaranteed
+/// to catch all panics, see the "Notes" section below.
+///
+/// The closure provided is required to adhere to the `UnwindSafe` trait to ensure
+/// that all captured variables are safe to cross this boundary. The purpose of
+/// this bound is to encode the concept of [exception safety][rfc] in the type
+/// system. Most usage of this function should not need to worry about this
+/// bound as programs are naturally unwind safe without `unsafe` code. If it
+/// becomes a problem the associated `AssertUnwindSafe` wrapper type in this
+/// module can be used to quickly assert that the usage here is indeed unwind
+/// safe.
+///
+/// [rfc]: https://github.com/rust-lang/rfcs/blob/master/text/1236-stabilize-catch-panic.md
+///
+/// # Notes
+///
+/// Note that this function **may not catch all panics** in Rust. A panic in
+/// Rust is not always implemented via unwinding, but can be implemented by
+/// aborting the process as well. This function *only* catches unwinding panics,
+/// not those that abort the process.
+///
+/// # Examples
+///
+/// ```
+/// use std::panic;
+///
+/// let result = panic::catch_unwind(|| {
+///     println!("hello!");
+/// });
+/// assert!(result.is_ok());
+///
+/// let result = panic::catch_unwind(|| {
+///     panic!("oh no!");
+/// });
+/// assert!(result.is_err());
+/// ```
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
+    unsafe {
+        panicking::try(f)
+    }
+}
+
+/// Triggers a panic without invoking the panic hook.
+///
+/// This is designed to be used in conjunction with `catch_unwind` to, for
+/// example, carry a panic across a layer of C code.
+///
+/// # Notes
+///
+/// Note that panics in Rust are not always implemented via unwinding, but they
+/// may be implemented by aborting the process. If this function is called when
+/// panics are implemented this way then this function will abort the process,
+/// not trigger an unwind.
+///
+/// # Examples
+///
+/// ```should_panic
+/// use std::panic;
+///
+/// let result = panic::catch_unwind(|| {
+///     panic!("oh no!");
+/// });
+///
+/// if let Err(err) = result {
+///     panic::resume_unwind(err);
+/// }
+/// ```
+#[stable(feature = "resume_unwind", since = "1.9.0")]
+// we always abort so I'm pretty sure there's no reason to ever call this
+pub fn resume_unwind(_payload: Box<Any + Send>) -> ! {
+    unimplemented!()
+}

ctr-std/src/panicking.rs

@@ -16,6 +16,9 @@ use io::prelude::*;
 use any::Any;
 use cell::RefCell;
 use fmt;
+use mem;
+use ptr;
+use raw;
 use __core::fmt::Display;
 
 thread_local! {
@@ -26,11 +29,11 @@ thread_local! {
 
 ///The compiler wants this to be here. Otherwise it won't be happy. And we like happy compilers.
 #[lang = "eh_personality"]
-extern fn eh_personality() {}
+pub extern fn eh_personality() {}
 
 /// Entry point of panic from the libcore crate.
 #[lang = "panic_fmt"]
-extern fn rust_begin_panic(msg: fmt::Arguments, file: &'static str, line: u32) -> ! {
+pub extern fn rust_begin_panic(msg: fmt::Arguments, file: &'static str, line: u32) -> ! {
     begin_panic_fmt(&msg, &(file, line))
 }
 
@@ -52,17 +55,127 @@ pub fn begin_panic_fmt(msg: &fmt::Arguments, file_line: &(&'static str, u32)) ->
     begin_panic(s, file_line);
 }
 
-/// This is where the main panic logic happens.
+/// We don't have stack unwinding, so all we do is print the panic message
+/// and then crash or hang the application
 #[inline(never)]
 #[cold]
 pub fn begin_panic<M: Any + Send + Display>(msg: M, file_line: &(&'static str, u32)) -> ! {
     let msg = Box::new(msg);
     let (file, line) = *file_line;
 
-    print!("--------------------------------------------------");
+    use libctru::console::consoleInit;
+    use libctru::gfx::gfxScreen_t;
+
+    // set up a new console, overwriting whatever was on the top screen
+    // before we started panicking
+    let _console = unsafe { consoleInit(gfxScreen_t::GFX_TOP, ptr::null_mut()) };
+
     println!("PANIC in {} at line {}:", file, line);
     println!("    {}", msg);
-    print!("\x1b[29;00H--------------------------------------------------");
 
+    // Terminate the process to ensure that all threads cease when panicking.
+    unsafe { ::libctru::svc::svcExitProcess() }
+
+    // On 3DS hardware, code execution will have terminated at the above function.
+    //
+    // Citra, however, will simply ignore the function and control flow becomes trapped
+    // in the following loop instead. However, this means that other threads may continue
+    // to run after a panic!
+    //
+    // This is actually a better outcome than calling libc::abort(), which seemingly
+    // causes the emulator to step into unreachable code, prompting it to freak out
+    // and spew endless nonsense into the console log.
     loop {}
 }
+
+/// Invoke a closure, capturing the cause of an unwinding panic if one occurs.
+pub unsafe fn try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<Any + Send>> {
+    #[allow(unions_with_drop_fields)]
+    union Data<F, R> {
+        f: F,
+        r: R,
+    }
+
+    // We do some sketchy operations with ownership here for the sake of
+    // performance. We can only  pass pointers down to
+    // `__rust_maybe_catch_panic` (can't pass objects by value), so we do all
+    // the ownership tracking here manually using a union.
+    //
+    // We go through a transition where:
+    //
+    // * First, we set the data to be the closure that we're going to call.
+    // * When we make the function call, the `do_call` function below, we take
+    //   ownership of the function pointer. At this point the `Data` union is
+    //   entirely uninitialized.
+    // * If the closure successfully returns, we write the return value into the
+    //   data's return slot. Note that `ptr::write` is used as it's overwriting
+    //   uninitialized data.
+    // * Finally, when we come back out of the `__rust_maybe_catch_panic` we're
+    //   in one of two states:
+    //
+    //      1. The closure didn't panic, in which case the return value was
+    //         filled in. We move it out of `data` and return it.
+    //      2. The closure panicked, in which case the return value wasn't
+    //         filled in. In this case the entire `data` union is invalid, so
+    //         there is no need to drop anything.
+    //
+    // Once we stack all that together we should have the "most efficient'
+    // method of calling a catch panic whilst juggling ownership.
+    let mut any_data = 0;
+    let mut any_vtable = 0;
+    let mut data = Data {
+        f: f,
+    };
+
+    let r = __rust_maybe_catch_panic(do_call::<F, R>,
+                                     &mut data as *mut _ as *mut u8,
+                                     &mut any_data,
+                                     &mut any_vtable);
+
+    return if r == 0 {
+        debug_assert!(update_panic_count(0) == 0);
+        Ok(data.r)
+    } else {
+        update_panic_count(-1);
+        debug_assert!(update_panic_count(0) == 0);
+        Err(mem::transmute(raw::TraitObject {
+            data: any_data as *mut _,
+            vtable: any_vtable as *mut _,
+        }))
+    };
+
+    fn do_call<F: FnOnce() -> R, R>(data: *mut u8) {
+        unsafe {
+            let data = data as *mut Data<F, R>;
+            let f = ptr::read(&mut (*data).f);
+            ptr::write(&mut (*data).r, f());
+        }
+    }
+}
+
+#[cfg(not(test))]
+#[doc(hidden)]
+#[unstable(feature = "update_panic_count", issue = "0")]
+pub fn update_panic_count(amt: isize) -> usize {
+    use cell::Cell;
+    thread_local! { static PANIC_COUNT: Cell<usize> = Cell::new(0) }
+
+    PANIC_COUNT.with(|c| {
+        let next = (c.get() as isize + amt) as usize;
+        c.set(next);
+        return next
+    })
+}
+
+// *Implementation borrowed from the libpanic_abort crate*
+//
+// Rust's "try" function, but if we're aborting on panics we just call the
+// function as there's nothing else we need to do here.
+#[allow(improper_ctypes)]
+extern fn __rust_maybe_catch_panic(f: fn(*mut u8),
+                                data: *mut u8,
+                                _data_ptr: *mut usize,
+								_vtable_ptr: *mut usize) -> u32 {
+    f(data);
+    0
+}

ctr-std/src/sync/barrier.rs

@@ -0,0 +1,233 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use fmt;
+use sync::{Mutex, Condvar};
+
+/// A barrier enables multiple threads to synchronize the beginning
+/// of some computation.
+///
+/// # Examples
+///
+/// ```
+/// use std::sync::{Arc, Barrier};
+/// use std::thread;
+///
+/// let mut handles = Vec::with_capacity(10);
+/// let barrier = Arc::new(Barrier::new(10));
+/// for _ in 0..10 {
+///     let c = barrier.clone();
+///     // The same messages will be printed together.
+///     // You will NOT see any interleaving.
+///     handles.push(thread::spawn(move|| {
+///         println!("before wait");
+///         c.wait();
+///         println!("after wait");
+///     }));
+/// }
+/// // Wait for other threads to finish.
+/// for handle in handles {
+///     handle.join().unwrap();
+/// }
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct Barrier {
+    lock: Mutex<BarrierState>,
+    cvar: Condvar,
+    num_threads: usize,
+}
+
+// The inner state of a double barrier
+struct BarrierState {
+    count: usize,
+    generation_id: usize,
+}
+
+/// A result returned from wait.
+///
+/// Currently this opaque structure only has one method, [`.is_leader()`]. Only
+/// one thread will receive a result that will return `true` from this function.
+///
+/// [`.is_leader()`]: #method.is_leader
+///
+/// # Examples
+///
+/// ```
+/// use std::sync::Barrier;
+///
+/// let barrier = Barrier::new(1);
+/// let barrier_wait_result = barrier.wait();
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct BarrierWaitResult(bool);
+
+#[stable(feature = "std_debug", since = "1.16.0")]
+impl fmt::Debug for Barrier {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("Barrier { .. }")
+    }
+}
+
+impl Barrier {
+    /// Creates a new barrier that can block a given number of threads.
+    ///
+    /// A barrier will block `n`-1 threads which call [`wait`] and then wake up
+    /// all threads at once when the `n`th thread calls [`wait`].
+    ///
+    /// [`wait`]: #method.wait
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::Barrier;
+    ///
+    /// let barrier = Barrier::new(10);
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn new(n: usize) -> Barrier {
+        Barrier {
+            lock: Mutex::new(BarrierState {
+                count: 0,
+                generation_id: 0,
+            }),
+            cvar: Condvar::new(),
+            num_threads: n,
+        }
+    }
+
+    /// Blocks the current thread until all threads have rendezvoused here.
+    ///
+    /// Barriers are re-usable after all threads have rendezvoused once, and can
+    /// be used continuously.
+    ///
+    /// A single (arbitrary) thread will receive a [`BarrierWaitResult`] that
+    /// returns `true` from [`is_leader`] when returning from this function, and
+    /// all other threads will receive a result that will return `false` from
+    /// [`is_leader`].
+    ///
+    /// [`BarrierWaitResult`]: struct.BarrierWaitResult.html
+    /// [`is_leader`]: struct.BarrierWaitResult.html#method.is_leader
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::{Arc, Barrier};
+    /// use std::thread;
+    ///
+    /// let mut handles = Vec::with_capacity(10);
+    /// let barrier = Arc::new(Barrier::new(10));
+    /// for _ in 0..10 {
+    ///     let c = barrier.clone();
+    ///     // The same messages will be printed together.
+    ///     // You will NOT see any interleaving.
+    ///     handles.push(thread::spawn(move|| {
+    ///         println!("before wait");
+    ///         c.wait();
+    ///         println!("after wait");
+    ///     }));
+    /// }
+    /// // Wait for other threads to finish.
+    /// for handle in handles {
+    ///     handle.join().unwrap();
+    /// }
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn wait(&self) -> BarrierWaitResult {
+        let mut lock = self.lock.lock().unwrap();
+        let local_gen = lock.generation_id;
+        lock.count += 1;
+        if lock.count < self.num_threads {
+            // We need a while loop to guard against spurious wakeups.
+            // http://en.wikipedia.org/wiki/Spurious_wakeup
+            while local_gen == lock.generation_id &&
+                  lock.count < self.num_threads {
+                lock = self.cvar.wait(lock).unwrap();
+            }
+            BarrierWaitResult(false)
+        } else {
+            lock.count = 0;
+            lock.generation_id += 1;
+            self.cvar.notify_all();
+            BarrierWaitResult(true)
+        }
+    }
+}
+
+#[stable(feature = "std_debug", since = "1.16.0")]
+impl fmt::Debug for BarrierWaitResult {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("BarrierWaitResult")
+            .field("is_leader", &self.is_leader())
+            .finish()
+    }
+}
+
+impl BarrierWaitResult {
+    /// Returns whether this thread from [`wait`] is the "leader thread".
+    ///
+    /// Only one thread will have `true` returned from their result, all other
+    /// threads will have `false` returned.
+    ///
+    /// [`wait`]: struct.Barrier.html#method.wait
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::Barrier;
+    ///
+    /// let barrier = Barrier::new(1);
+    /// let barrier_wait_result = barrier.wait();
+    /// println!("{:?}", barrier_wait_result.is_leader());
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn is_leader(&self) -> bool { self.0 }
+}
+
+#[cfg(test)]
+mod tests {
+    use sync::{Arc, Barrier};
+    use sync::mpsc::{channel, TryRecvError};
+    use thread;
+
+    #[test]
+    #[cfg_attr(target_os = "emscripten", ignore)]
+    fn test_barrier() {
+        const N: usize = 10;
+
+        let barrier = Arc::new(Barrier::new(N));
+        let (tx, rx) = channel();
+
+        for _ in 0..N - 1 {
+            let c = barrier.clone();
+            let tx = tx.clone();
+            thread::spawn(move|| {
+                tx.send(c.wait().is_leader()).unwrap();
+            });
+        }
+
+        // At this point, all spawned threads should be blocked,
+        // so we shouldn't get anything from the port
+        assert!(match rx.try_recv() {
+            Err(TryRecvError::Empty) => true,
+            _ => false,
+        });
+
+        let mut leader_found = barrier.wait().is_leader();
+
+        // Now, the barrier is cleared and we should get data.
+        for _ in 0..N - 1 {
+            if rx.recv().unwrap() {
+                assert!(!leader_found);
+                leader_found = true;
+            }
+        }
+        assert!(leader_found);
+    }
+}

ctr-std/src/sync/condvar.rs

@@ -0,0 +1,589 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use fmt;
+use sync::atomic::{AtomicUsize, Ordering};
+use sync::{mutex, MutexGuard, PoisonError};
+use sys_common::condvar as sys;
+use sys_common::mutex as sys_mutex;
+use sys_common::poison::{self, LockResult};
+use time::Duration;
+
+/// A type indicating whether a timed wait on a condition variable returned
+/// due to a time out or not.
+///
+/// It is returned by the [`wait_timeout`] method.
+///
+/// [`wait_timeout`]: struct.Condvar.html#method.wait_timeout
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+#[stable(feature = "wait_timeout", since = "1.5.0")]
+pub struct WaitTimeoutResult(bool);
+
+impl WaitTimeoutResult {
+    /// Returns whether the wait was known to have timed out.
+    ///
+    /// # Examples
+    ///
+    /// This example spawns a thread which will update the boolean value and
+    /// then wait 100 milliseconds before notifying the condvar.
+    ///
+    /// The main thread will wait with a timeout on the condvar and then leave
+    /// once the boolean has been updated and notified.
+    ///
+    /// ```
+    /// use std::sync::{Arc, Mutex, Condvar};
+    /// use std::thread;
+    /// use std::time::Duration;
+    ///
+    /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
+    /// let pair2 = pair.clone();
+    ///
+    /// thread::spawn(move|| {
+    ///     let &(ref lock, ref cvar) = &*pair2;
+    ///     let mut started = lock.lock().unwrap();
+    ///     // We update the boolean value.
+    ///     *started = true;
+    ///     // Let's wait 20 milliseconds before notifying the condvar.
+    ///     thread::sleep(Duration::from_millis(20));
+    ///     cvar.notify_one();
+    /// });
+    ///
+    /// // Wait for the thread to start up.
+    /// let &(ref lock, ref cvar) = &*pair;
+    /// let mut started = lock.lock().unwrap();
+    /// loop {
+    ///     // Let's put a timeout on the condvar's wait.
+    ///     let result = cvar.wait_timeout(started, Duration::from_millis(10)).unwrap();
+    ///     // 10 milliseconds have passed, or maybe the value changed!
+    ///     started = result.0;
+    ///     if *started == true {
+    ///         // We received the notification and the value has been updated, we can leave.
+    ///         break
+    ///     }
+    /// }
+    /// ```
+    #[stable(feature = "wait_timeout", since = "1.5.0")]
+    pub fn timed_out(&self) -> bool {
+        self.0
+    }
+}
+
+/// A Condition Variable
+///
+/// Condition variables represent the ability to block a thread such that it
+/// consumes no CPU time while waiting for an event to occur. Condition
+/// variables are typically associated with a boolean predicate (a condition)
+/// and a mutex. The predicate is always verified inside of the mutex before
+/// determining that a thread must block.
+///
+/// Functions in this module will block the current **thread** of execution and
+/// are bindings to system-provided condition variables where possible. Note
+/// that this module places one additional restriction over the system condition
+/// variables: each condvar can be used with precisely one mutex at runtime. Any
+/// attempt to use multiple mutexes on the same condition variable will result
+/// in a runtime panic. If this is not desired, then the unsafe primitives in
+/// `sys` do not have this restriction but may result in undefined behavior.
+///
+/// # Examples
+///
+/// ```
+/// use std::sync::{Arc, Mutex, Condvar};
+/// use std::thread;
+///
+/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
+/// let pair2 = pair.clone();
+///
+/// // Inside of our lock, spawn a new thread, and then wait for it to start.
+/// thread::spawn(move|| {
+///     let &(ref lock, ref cvar) = &*pair2;
+///     let mut started = lock.lock().unwrap();
+///     *started = true;
+///     // We notify the condvar that the value has changed.
+///     cvar.notify_one();
+/// });
+///
+/// // Wait for the thread to start up.
+/// let &(ref lock, ref cvar) = &*pair;
+/// let mut started = lock.lock().unwrap();
+/// while !*started {
+///     started = cvar.wait(started).unwrap();
+/// }
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct Condvar {
+    inner: Box<sys::Condvar>,
+    mutex: AtomicUsize,
+}
+
+impl Condvar {
+    /// Creates a new condition variable which is ready to be waited on and
+    /// notified.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::Condvar;
+    ///
+    /// let condvar = Condvar::new();
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn new() -> Condvar {
+        let mut c = Condvar {
+            inner: box sys::Condvar::new(),
+            mutex: AtomicUsize::new(0),
+        };
+        unsafe {
+            c.inner.init();
+        }
+        c
+    }
+
+    /// Blocks the current thread until this condition variable receives a
+    /// notification.
+    ///
+    /// This function will atomically unlock the mutex specified (represented by
+    /// `guard`) and block the current thread. This means that any calls
+    /// to [`notify_one()`] or [`notify_all()`] which happen logically after the
+    /// mutex is unlocked are candidates to wake this thread up. When this
+    /// function call returns, the lock specified will have been re-acquired.
+    ///
+    /// Note that this function is susceptible to spurious wakeups. Condition
+    /// variables normally have a boolean predicate associated with them, and
+    /// the predicate must always be checked each time this function returns to
+    /// protect against spurious wakeups.
+    ///
+    /// # Errors
+    ///
+    /// This function will return an error if the mutex being waited on is
+    /// poisoned when this thread re-acquires the lock. For more information,
+    /// see information about [poisoning] on the [`Mutex`] type.
+    ///
+    /// # Panics
+    ///
+    /// This function will [`panic!()`] if it is used with more than one mutex
+    /// over time. Each condition variable is dynamically bound to exactly one
+    /// mutex to ensure defined behavior across platforms. If this functionality
+    /// is not desired, then unsafe primitives in `sys` are provided.
+    ///
+    /// [`notify_one()`]: #method.notify_one
+    /// [`notify_all()`]: #method.notify_all
+    /// [poisoning]: ../sync/struct.Mutex.html#poisoning
+    /// [`Mutex`]: ../sync/struct.Mutex.html
+    /// [`panic!()`]: ../../std/macro.panic.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::{Arc, Mutex, Condvar};
+    /// use std::thread;
+    ///
+    /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
+    /// let pair2 = pair.clone();
+    ///
+    /// thread::spawn(move|| {
+    ///     let &(ref lock, ref cvar) = &*pair2;
+    ///     let mut started = lock.lock().unwrap();
+    ///     *started = true;
+    ///     // We notify the condvar that the value has changed.
+    ///     cvar.notify_one();
+    /// });
+    ///
+    /// // Wait for the thread to start up.
+    /// let &(ref lock, ref cvar) = &*pair;
+    /// let mut started = lock.lock().unwrap();
+    /// // As long as the value inside the `Mutex` is false, we wait.
+    /// while !*started {
+    ///     started = cvar.wait(started).unwrap();
+    /// }
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn wait<'a, T>(&self, guard: MutexGuard<'a, T>)
+                       -> LockResult<MutexGuard<'a, T>> {
+        let poisoned = unsafe {
+            let lock = mutex::guard_lock(&guard);
+            self.verify(lock);
+            self.inner.wait(lock);
+            mutex::guard_poison(&guard).get()
+        };
+        if poisoned {
+            Err(PoisonError::new(guard))
+        } else {
+            Ok(guard)
+        }
+    }
+
+    /// Waits on this condition variable for a notification, timing out after a
+    /// specified duration.
+    ///
+    /// The semantics of this function are equivalent to [`wait`]
+    /// except that the thread will be blocked for roughly no longer
+    /// than `ms` milliseconds. This method should not be used for
+    /// precise timing due to anomalies such as preemption or platform
+    /// differences that may not cause the maximum amount of time
+    /// waited to be precisely `ms`.
+    ///
+    /// Note that the best effort is made to ensure that the time waited is
+    /// measured with a monotonic clock, and not affected by the changes made to
+    /// the system time.
+    ///
+    /// The returned boolean is `false` only if the timeout is known
+    /// to have elapsed.
+    ///
+    /// Like [`wait`], the lock specified will be re-acquired when this function
+    /// returns, regardless of whether the timeout elapsed or not.
+    ///
+    /// [`wait`]: #method.wait
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::{Arc, Mutex, Condvar};
+    /// use std::thread;
+    ///
+    /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
+    /// let pair2 = pair.clone();
+    ///
+    /// thread::spawn(move|| {
+    ///     let &(ref lock, ref cvar) = &*pair2;
+    ///     let mut started = lock.lock().unwrap();
+    ///     *started = true;
+    ///     // We notify the condvar that the value has changed.
+    ///     cvar.notify_one();
+    /// });
+    ///
+    /// // Wait for the thread to start up.
+    /// let &(ref lock, ref cvar) = &*pair;
+    /// let mut started = lock.lock().unwrap();
+    /// // As long as the value inside the `Mutex` is false, we wait.
+    /// loop {
+    ///     let result = cvar.wait_timeout_ms(started, 10).unwrap();
+    ///     // 10 milliseconds have passed, or maybe the value changed!
+    ///     started = result.0;
+    ///     if *started == true {
+    ///         // We received the notification and the value has been updated, we can leave.
+    ///         break
+    ///     }
+    /// }
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::sync::Condvar::wait_timeout`")]
+    pub fn wait_timeout_ms<'a, T>(&self, guard: MutexGuard<'a, T>, ms: u32)
+                                  -> LockResult<(MutexGuard<'a, T>, bool)> {
+        let res = self.wait_timeout(guard, Duration::from_millis(ms as u64));
+        poison::map_result(res, |(a, b)| {
+            (a, !b.timed_out())
+        })
+    }
+
+    /// Waits on this condition variable for a notification, timing out after a
+    /// specified duration.
+    ///
+    /// The semantics of this function are equivalent to [`wait`] except that
+    /// the thread will be blocked for roughly no longer than `dur`. This
+    /// method should not be used for precise timing due to anomalies such as
+    /// preemption or platform differences that may not cause the maximum
+    /// amount of time waited to be precisely `dur`.
+    ///
+    /// Note that the best effort is made to ensure that the time waited is
+    /// measured with a monotonic clock, and not affected by the changes made to
+    /// the system time.
+    ///
+    /// The returned [`WaitTimeoutResult`] value indicates if the timeout is
+    /// known to have elapsed.
+    ///
+    /// Like [`wait`], the lock specified will be re-acquired when this function
+    /// returns, regardless of whether the timeout elapsed or not.
+    ///
+    /// [`wait`]: #method.wait
+    /// [`WaitTimeoutResult`]: struct.WaitTimeoutResult.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::{Arc, Mutex, Condvar};
+    /// use std::thread;
+    /// use std::time::Duration;
+    ///
+    /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
+    /// let pair2 = pair.clone();
+    ///
+    /// thread::spawn(move|| {
+    ///     let &(ref lock, ref cvar) = &*pair2;
+    ///     let mut started = lock.lock().unwrap();
+    ///     *started = true;
+    ///     // We notify the condvar that the value has changed.
+    ///     cvar.notify_one();
+    /// });
+    ///
+    /// // wait for the thread to start up
+    /// let &(ref lock, ref cvar) = &*pair;
+    /// let mut started = lock.lock().unwrap();
+    /// // as long as the value inside the `Mutex` is false, we wait
+    /// loop {
+    ///     let result = cvar.wait_timeout(started, Duration::from_millis(10)).unwrap();
+    ///     // 10 milliseconds have passed, or maybe the value changed!
+    ///     started = result.0;
+    ///     if *started == true {
+    ///         // We received the notification and the value has been updated, we can leave.
+    ///         break
+    ///     }
+    /// }
+    /// ```
+    #[stable(feature = "wait_timeout", since = "1.5.0")]
+    pub fn wait_timeout<'a, T>(&self, guard: MutexGuard<'a, T>,
+                               dur: Duration)
+                               -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)> {
+        let (poisoned, result) = unsafe {
+            let lock = mutex::guard_lock(&guard);
+            self.verify(lock);
+            let success = self.inner.wait_timeout(lock, dur);
+            (mutex::guard_poison(&guard).get(), WaitTimeoutResult(!success))
+        };
+        if poisoned {
+            Err(PoisonError::new((guard, result)))
+        } else {
+            Ok((guard, result))
+        }
+    }
+
+    /// Wakes up one blocked thread on this condvar.
+    ///
+    /// If there is a blocked thread on this condition variable, then it will
+    /// be woken up from its call to [`wait`] or [`wait_timeout`]. Calls to
+    /// `notify_one` are not buffered in any way.
+    ///
+    /// To wake up all threads, see [`notify_all()`].
+    ///
+    /// [`wait`]: #method.wait
+    /// [`wait_timeout`]: #method.wait_timeout
+    /// [`notify_all()`]: #method.notify_all
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::{Arc, Mutex, Condvar};
+    /// use std::thread;
+    ///
+    /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
+    /// let pair2 = pair.clone();
+    ///
+    /// thread::spawn(move|| {
+    ///     let &(ref lock, ref cvar) = &*pair2;
+    ///     let mut started = lock.lock().unwrap();
+    ///     *started = true;
+    ///     // We notify the condvar that the value has changed.
+    ///     cvar.notify_one();
+    /// });
+    ///
+    /// // Wait for the thread to start up.
+    /// let &(ref lock, ref cvar) = &*pair;
+    /// let mut started = lock.lock().unwrap();
+    /// // As long as the value inside the `Mutex` is false, we wait.
+    /// while !*started {
+    ///     started = cvar.wait(started).unwrap();
+    /// }
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn notify_one(&self) {
+        unsafe { self.inner.notify_one() }
+    }
+
+    /// Wakes up all blocked threads on this condvar.
+    ///
+    /// This method will ensure that any current waiters on the condition
+    /// variable are awoken. Calls to `notify_all()` are not buffered in any
+    /// way.
+    ///
+    /// To wake up only one thread, see [`notify_one()`].
+    ///
+    /// [`notify_one()`]: #method.notify_one
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::{Arc, Mutex, Condvar};
+    /// use std::thread;
+    ///
+    /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
+    /// let pair2 = pair.clone();
+    ///
+    /// thread::spawn(move|| {
+    ///     let &(ref lock, ref cvar) = &*pair2;
+    ///     let mut started = lock.lock().unwrap();
+    ///     *started = true;
+    ///     // We notify the condvar that the value has changed.
+    ///     cvar.notify_all();
+    /// });
+    ///
+    /// // Wait for the thread to start up.
+    /// let &(ref lock, ref cvar) = &*pair;
+    /// let mut started = lock.lock().unwrap();
+    /// // As long as the value inside the `Mutex` is false, we wait.
+    /// while !*started {
+    ///     started = cvar.wait(started).unwrap();
+    /// }
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn notify_all(&self) {
+        unsafe { self.inner.notify_all() }
+    }
+
+    fn verify(&self, mutex: &sys_mutex::Mutex) {
+        let addr = mutex as *const _ as usize;
+        match self.mutex.compare_and_swap(0, addr, Ordering::SeqCst) {
+            // If we got out 0, then we have successfully bound the mutex to
+            // this cvar.
+            0 => {}
+
+            // If we get out a value that's the same as `addr`, then someone
+            // already beat us to the punch.
+            n if n == addr => {}
+
+            // Anything else and we're using more than one mutex on this cvar,
+            // which is currently disallowed.
+            _ => panic!("attempted to use a condition variable with two \
+                         mutexes"),
+        }
+    }
+}
+
+#[stable(feature = "std_debug", since = "1.16.0")]
+impl fmt::Debug for Condvar {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("Condvar { .. }")
+    }
+}
+
+#[stable(feature = "condvar_default", since = "1.9.0")]
+impl Default for Condvar {
+    /// Creates a `Condvar` which is ready to be waited on and notified.
+    fn default() -> Condvar {
+        Condvar::new()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Drop for Condvar {
+    fn drop(&mut self) {
+        unsafe { self.inner.destroy() }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use sync::mpsc::channel;
+    use sync::{Condvar, Mutex, Arc};
+    use thread;
+    use time::Duration;
+    use u32;
+
+    #[test]
+    fn smoke() {
+        let c = Condvar::new();
+        c.notify_one();
+        c.notify_all();
+    }
+
+    #[test]
+    #[cfg_attr(target_os = "emscripten", ignore)]
+    fn notify_one() {
+        let m = Arc::new(Mutex::new(()));
+        let m2 = m.clone();
+        let c = Arc::new(Condvar::new());
+        let c2 = c.clone();
+
+        let g = m.lock().unwrap();
+        let _t = thread::spawn(move|| {
+            let _g = m2.lock().unwrap();
+            c2.notify_one();
+        });
+        let g = c.wait(g).unwrap();
+        drop(g);
+    }
+
+    #[test]
+    #[cfg_attr(target_os = "emscripten", ignore)]
+    fn notify_all() {
+        const N: usize = 10;
+
+        let data = Arc::new((Mutex::new(0), Condvar::new()));
+        let (tx, rx) = channel();
+        for _ in 0..N {
+            let data = data.clone();
+            let tx = tx.clone();
+            thread::spawn(move|| {
+                let &(ref lock, ref cond) = &*data;
+                let mut cnt = lock.lock().unwrap();
+                *cnt += 1;
+                if *cnt == N {
+                    tx.send(()).unwrap();
+                }
+                while *cnt != 0 {
+                    cnt = cond.wait(cnt).unwrap();
+                }
+                tx.send(()).unwrap();
+            });
+        }
+        drop(tx);
+
+        let &(ref lock, ref cond) = &*data;
+        rx.recv().unwrap();
+        let mut cnt = lock.lock().unwrap();
+        *cnt = 0;
+        cond.notify_all();
+        drop(cnt);
+
+        for _ in 0..N {
+            rx.recv().unwrap();
+        }
+    }
+
+    #[test]
+    #[cfg_attr(target_os = "emscripten", ignore)]
+    fn wait_timeout_ms() {
+        let m = Arc::new(Mutex::new(()));
+        let m2 = m.clone();
+        let c = Arc::new(Condvar::new());
+        let c2 = c.clone();
+
+        let g = m.lock().unwrap();
+        let (g, _no_timeout) = c.wait_timeout(g, Duration::from_millis(1)).unwrap();
+        // spurious wakeups mean this isn't necessarily true
+        // assert!(!no_timeout);
+        let _t = thread::spawn(move || {
+            let _g = m2.lock().unwrap();
+            c2.notify_one();
+        });
+        let (g, timeout_res) = c.wait_timeout(g, Duration::from_millis(u32::MAX as u64)).unwrap();
+        assert!(!timeout_res.timed_out());
+        drop(g);
+    }
+
+    #[test]
+    #[should_panic]
+    #[cfg_attr(target_os = "emscripten", ignore)]
+    fn two_mutexes() {
+        let m = Arc::new(Mutex::new(()));
+        let m2 = m.clone();
+        let c = Arc::new(Condvar::new());
+        let c2 = c.clone();
+
+        let mut g = m.lock().unwrap();
+        let _t = thread::spawn(move|| {
+            let _g = m2.lock().unwrap();
+            c2.notify_one();
+        });
+        g = c.wait(g).unwrap();
+        drop(g);
+
+        let m = Mutex::new(());
+        let _ = c.wait(m.lock().unwrap()).unwrap();
+    }
+}

ctr-std/src/sync/mod.rs

@@ -21,9 +21,24 @@
 pub use alloc::arc::{Arc, Weak};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::sync::atomic;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use self::barrier::{Barrier, BarrierWaitResult};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use self::condvar::{Condvar, WaitTimeoutResult};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::mutex::{Mutex, MutexGuard};
 #[stable(feature = "rust1", since = "1.0.0")]
+pub use self::once::{Once, OnceState, ONCE_INIT};
+#[stable(feature = "rust1", since = "1.0.0")]
 pub use sys_common::poison::{PoisonError, TryLockError, TryLockResult, LockResult};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use self::rwlock::{RwLock, RwLockReadGuard, RwLockWriteGuard};
+
+pub mod mpsc;
 
+mod barrier;
+mod condvar;
 mod mutex;
+mod once;
+mod rwlock;

ctr-std/src/sync/mpsc/blocking.rs

@@ -0,0 +1,96 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Generic support for building blocking abstractions.
+
+use thread::{self, Thread};
+use sync::atomic::{AtomicBool, Ordering};
+use sync::Arc;
+use mem;
+use time::Instant;
+
+struct Inner {
+    thread: Thread,
+    woken: AtomicBool,
+}
+
+unsafe impl Send for Inner {}
+unsafe impl Sync for Inner {}
+
+#[derive(Clone)]
+pub struct SignalToken {
+    inner: Arc<Inner>,
+}
+
+pub struct WaitToken {
+    inner: Arc<Inner>,
+}
+
+impl !Send for WaitToken {}
+
+impl !Sync for WaitToken {}
+
+pub fn tokens() -> (WaitToken, SignalToken) {
+    let inner = Arc::new(Inner {
+        thread: thread::current(),
+        woken: AtomicBool::new(false),
+    });
+    let wait_token = WaitToken {
+        inner: inner.clone(),
+    };
+    let signal_token = SignalToken {
+        inner: inner
+    };
+    (wait_token, signal_token)
+}
+
+impl SignalToken {
+    pub fn signal(&self) -> bool {
+        let wake = !self.inner.woken.compare_and_swap(false, true, Ordering::SeqCst);
+        if wake {
+            self.inner.thread.unpark();
+        }
+        wake
+    }
+
+    /// Convert to an unsafe usize value. Useful for storing in a pipe's state
+    /// flag.
+    #[inline]
+    pub unsafe fn cast_to_usize(self) -> usize {
+        mem::transmute(self.inner)
+    }
+
+    /// Convert from an unsafe usize value. Useful for retrieving a pipe's state
+    /// flag.
+    #[inline]
+    pub unsafe fn cast_from_usize(signal_ptr: usize) -> SignalToken {
+        SignalToken { inner: mem::transmute(signal_ptr) }
+    }
+}
+
+impl WaitToken {
+    pub fn wait(self) {
+        while !self.inner.woken.load(Ordering::SeqCst) {
+            thread::park()
+        }
+    }
+
+    /// Returns true if we wake up normally, false otherwise.
+    pub fn wait_max_until(self, end: Instant) -> bool {
+        while !self.inner.woken.load(Ordering::SeqCst) {
+            let now = Instant::now();
+            if now >= end {
+                return false;
+            }
+            thread::park_timeout(end - now)
+        }
+        true
+    }
+}

ctr-std/src/sync/mpsc/mpsc_queue.rs

@@ -0,0 +1,198 @@
+/* Copyright (c) 2010-2011 Dmitry Vyukov. All rights reserved.
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *    1. Redistributions of source code must retain the above copyright notice,
+ *       this list of conditions and the following disclaimer.
+ *
+ *    2. Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY DMITRY VYUKOV "AS IS" AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+ * SHALL DMITRY VYUKOV OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * The views and conclusions contained in the software and documentation are
+ * those of the authors and should not be interpreted as representing official
+ * policies, either expressed or implied, of Dmitry Vyukov.
+ */
+
+//! A mostly lock-free multi-producer, single consumer queue.
+//!
+//! This module contains an implementation of a concurrent MPSC queue. This
+//! queue can be used to share data between threads, and is also used as the
+//! building block of channels in rust.
+//!
+//! Note that the current implementation of this queue has a caveat of the `pop`
+//! method, and see the method for more information about it. Due to this
+//! caveat, this queue may not be appropriate for all use-cases.
+
+// http://www.1024cores.net/home/lock-free-algorithms
+//                         /queues/non-intrusive-mpsc-node-based-queue
+
+pub use self::PopResult::*;
+
+use alloc::boxed::Box;
+use core::ptr;
+use core::cell::UnsafeCell;
+
+use sync::atomic::{AtomicPtr, Ordering};
+
+/// A result of the `pop` function.
+pub enum PopResult<T> {
+    /// Some data has been popped
+    Data(T),
+    /// The queue is empty
+    Empty,
+    /// The queue is in an inconsistent state. Popping data should succeed, but
+    /// some pushers have yet to make enough progress in order allow a pop to
+    /// succeed. It is recommended that a pop() occur "in the near future" in
+    /// order to see if the sender has made progress or not
+    Inconsistent,
+}
+
+struct Node<T> {
+    next: AtomicPtr<Node<T>>,
+    value: Option<T>,
+}
+
+/// The multi-producer single-consumer structure. This is not cloneable, but it
+/// may be safely shared so long as it is guaranteed that there is only one
+/// popper at a time (many pushers are allowed).
+pub struct Queue<T> {
+    head: AtomicPtr<Node<T>>,
+    tail: UnsafeCell<*mut Node<T>>,
+}
+
+unsafe impl<T: Send> Send for Queue<T> { }
+unsafe impl<T: Send> Sync for Queue<T> { }
+
+impl<T> Node<T> {
+    unsafe fn new(v: Option<T>) -> *mut Node<T> {
+        Box::into_raw(box Node {
+            next: AtomicPtr::new(ptr::null_mut()),
+            value: v,
+        })
+    }
+}
+
+impl<T> Queue<T> {
+    /// Creates a new queue that is safe to share among multiple producers and
+    /// one consumer.
+    pub fn new() -> Queue<T> {
+        let stub = unsafe { Node::new(None) };
+        Queue {
+            head: AtomicPtr::new(stub),
+            tail: UnsafeCell::new(stub),
+        }
+    }
+
+    /// Pushes a new value onto this queue.
+    pub fn push(&self, t: T) {
+        unsafe {
+            let n = Node::new(Some(t));
+            let prev = self.head.swap(n, Ordering::AcqRel);
+            (*prev).next.store(n, Ordering::Release);
+        }
+    }
+
+    /// Pops some data from this queue.
+    ///
+    /// Note that the current implementation means that this function cannot
+    /// return `Option<T>`. It is possible for this queue to be in an
+    /// inconsistent state where many pushes have succeeded and completely
+    /// finished, but pops cannot return `Some(t)`. This inconsistent state
+    /// happens when a pusher is pre-empted at an inopportune moment.
+    ///
+    /// This inconsistent state means that this queue does indeed have data, but
+    /// it does not currently have access to it at this time.
+    pub fn pop(&self) -> PopResult<T> {
+        unsafe {
+            let tail = *self.tail.get();
+            let next = (*tail).next.load(Ordering::Acquire);
+
+            if !next.is_null() {
+                *self.tail.get() = next;
+                assert!((*tail).value.is_none());
+                assert!((*next).value.is_some());
+                let ret = (*next).value.take().unwrap();
+                let _: Box<Node<T>> = Box::from_raw(tail);
+                return Data(ret);
+            }
+
+            if self.head.load(Ordering::Acquire) == tail {Empty} else {Inconsistent}
+        }
+    }
+}
+
+impl<T> Drop for Queue<T> {
+    fn drop(&mut self) {
+        unsafe {
+            let mut cur = *self.tail.get();
+            while !cur.is_null() {
+                let next = (*cur).next.load(Ordering::Relaxed);
+                let _: Box<Node<T>> = Box::from_raw(cur);
+                cur = next;
+            }
+        }
+    }
+}
+
+#[cfg(all(test, not(target_os = "emscripten")))]
+mod tests {
+    use sync::mpsc::channel;
+    use super::{Queue, Data, Empty, Inconsistent};
+    use sync::Arc;
+    use thread;
+
+    #[test]
+    fn test_full() {
+        let q: Queue<Box<_>> = Queue::new();
+        q.push(box 1);
+        q.push(box 2);
+    }
+
+    #[test]
+    fn test() {
+        let nthreads = 8;
+        let nmsgs = 1000;
+        let q = Queue::new();
+        match q.pop() {
+            Empty => {}
+            Inconsistent | Data(..) => panic!()
+        }
+        let (tx, rx) = channel();
+        let q = Arc::new(q);
+
+        for _ in 0..nthreads {
+            let tx = tx.clone();
+            let q = q.clone();
+            thread::spawn(move|| {
+                for i in 0..nmsgs {
+                    q.push(i);
+                }
+                tx.send(()).unwrap();
+            });
+        }
+
+        let mut i = 0;
+        while i < nthreads * nmsgs {
+            match q.pop() {
+                Empty | Inconsistent => {},
+                Data(_) => { i += 1 }
+            }
+        }
+        drop(tx);
+        for _ in 0..nthreads {
+            rx.recv().unwrap();
+        }
+    }
+}

ctr-std/src/sync/mpsc/oneshot.rs

@@ -0,0 +1,396 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/// Oneshot channels/ports
+///
+/// This is the initial flavor of channels/ports used for comm module. This is
+/// an optimization for the one-use case of a channel. The major optimization of
+/// this type is to have one and exactly one allocation when the chan/port pair
+/// is created.
+///
+/// Another possible optimization would be to not use an Arc box because
+/// in theory we know when the shared packet can be deallocated (no real need
+/// for the atomic reference counting), but I was having trouble how to destroy
+/// the data early in a drop of a Port.
+///
+/// # Implementation
+///
+/// Oneshots are implemented around one atomic usize variable. This variable
+/// indicates both the state of the port/chan but also contains any threads
+/// blocked on the port. All atomic operations happen on this one word.
+///
+/// In order to upgrade a oneshot channel, an upgrade is considered a disconnect
+/// on behalf of the channel side of things (it can be mentally thought of as
+/// consuming the port). This upgrade is then also stored in the shared packet.
+/// The one caveat to consider is that when a port sees a disconnected channel
+/// it must check for data because there is no "data plus upgrade" state.
+
+pub use self::Failure::*;
+pub use self::UpgradeResult::*;
+pub use self::SelectionResult::*;
+use self::MyUpgrade::*;
+
+use sync::mpsc::Receiver;
+use sync::mpsc::blocking::{self, SignalToken};
+use cell::UnsafeCell;
+use ptr;
+use sync::atomic::{AtomicUsize, Ordering};
+use time::Instant;
+
+// Various states you can find a port in.
+const EMPTY: usize = 0;          // initial state: no data, no blocked receiver
+const DATA: usize = 1;           // data ready for receiver to take
+const DISCONNECTED: usize = 2;   // channel is disconnected OR upgraded
+// Any other value represents a pointer to a SignalToken value. The
+// protocol ensures that when the state moves *to* a pointer,
+// ownership of the token is given to the packet, and when the state
+// moves *from* a pointer, ownership of the token is transferred to
+// whoever changed the state.
+
+pub struct Packet<T> {
+    // Internal state of the chan/port pair (stores the blocked thread as well)
+    state: AtomicUsize,
+    // One-shot data slot location
+    data: UnsafeCell<Option<T>>,
+    // when used for the second time, a oneshot channel must be upgraded, and
+    // this contains the slot for the upgrade
+    upgrade: UnsafeCell<MyUpgrade<T>>,
+}
+
+pub enum Failure<T> {
+    Empty,
+    Disconnected,
+    Upgraded(Receiver<T>),
+}
+
+pub enum UpgradeResult {
+    UpSuccess,
+    UpDisconnected,
+    UpWoke(SignalToken),
+}
+
+pub enum SelectionResult<T> {
+    SelCanceled,
+    SelUpgraded(SignalToken, Receiver<T>),
+    SelSuccess,
+}
+
+enum MyUpgrade<T> {
+    NothingSent,
+    SendUsed,
+    GoUp(Receiver<T>),
+}
+
+impl<T> Packet<T> {
+    pub fn new() -> Packet<T> {
+        Packet {
+            data: UnsafeCell::new(None),
+            upgrade: UnsafeCell::new(NothingSent),
+            state: AtomicUsize::new(EMPTY),
+        }
+    }
+
+    pub fn send(&self, t: T) -> Result<(), T> {
+        unsafe {
+            // Sanity check
+            match *self.upgrade.get() {
+                NothingSent => {}
+                _ => panic!("sending on a oneshot that's already sent on "),
+            }
+            assert!((*self.data.get()).is_none());
+            ptr::write(self.data.get(), Some(t));
+            ptr::write(self.upgrade.get(), SendUsed);
+
+            match self.state.swap(DATA, Ordering::SeqCst) {
+                // Sent the data, no one was waiting
+                EMPTY => Ok(()),
+
+                // Couldn't send the data, the port hung up first. Return the data
+                // back up the stack.
+                DISCONNECTED => {
+                    self.state.swap(DISCONNECTED, Ordering::SeqCst);
+                    ptr::write(self.upgrade.get(), NothingSent);
+                    Err((&mut *self.data.get()).take().unwrap())
+                }
+
+                // Not possible, these are one-use channels
+                DATA => unreachable!(),
+
+                // There is a thread waiting on the other end. We leave the 'DATA'
+                // state inside so it'll pick it up on the other end.
+                ptr => {
+                    SignalToken::cast_from_usize(ptr).signal();
+                    Ok(())
+                }
+            }
+        }
+    }
+
+    // Just tests whether this channel has been sent on or not, this is only
+    // safe to use from the sender.
+    pub fn sent(&self) -> bool {
+        unsafe {
+            match *self.upgrade.get() {
+                NothingSent => false,
+                _ => true,
+            }
+        }
+    }
+
+    pub fn recv(&self, deadline: Option<Instant>) -> Result<T, Failure<T>> {
+        // Attempt to not block the thread (it's a little expensive). If it looks
+        // like we're not empty, then immediately go through to `try_recv`.
+        if self.state.load(Ordering::SeqCst) == EMPTY {
+            let (wait_token, signal_token) = blocking::tokens();
+            let ptr = unsafe { signal_token.cast_to_usize() };
+
+            // race with senders to enter the blocking state
+            if self.state.compare_and_swap(EMPTY, ptr, Ordering::SeqCst) == EMPTY {
+                if let Some(deadline) = deadline {
+                    let timed_out = !wait_token.wait_max_until(deadline);
+                    // Try to reset the state
+                    if timed_out {
+                        self.abort_selection().map_err(Upgraded)?;
+                    }
+                } else {
+                    wait_token.wait();
+                    debug_assert!(self.state.load(Ordering::SeqCst) != EMPTY);
+                }
+            } else {
+                // drop the signal token, since we never blocked
+                drop(unsafe { SignalToken::cast_from_usize(ptr) });
+            }
+        }
+
+        self.try_recv()
+    }
+
+    pub fn try_recv(&self) -> Result<T, Failure<T>> {
+        unsafe {
+            match self.state.load(Ordering::SeqCst) {
+                EMPTY => Err(Empty),
+
+                // We saw some data on the channel, but the channel can be used
+                // again to send us an upgrade. As a result, we need to re-insert
+                // into the channel that there's no data available (otherwise we'll
+                // just see DATA next time). This is done as a cmpxchg because if
+                // the state changes under our feet we'd rather just see that state
+                // change.
+                DATA => {
+                    self.state.compare_and_swap(DATA, EMPTY, Ordering::SeqCst);
+                    match (&mut *self.data.get()).take() {
+                        Some(data) => Ok(data),
+                        None => unreachable!(),
+                    }
+                }
+
+                // There's no guarantee that we receive before an upgrade happens,
+                // and an upgrade flags the channel as disconnected, so when we see
+                // this we first need to check if there's data available and *then*
+                // we go through and process the upgrade.
+                DISCONNECTED => {
+                    match (&mut *self.data.get()).take() {
+                        Some(data) => Ok(data),
+                        None => {
+                            match ptr::replace(self.upgrade.get(), SendUsed) {
+                                SendUsed | NothingSent => Err(Disconnected),
+                                GoUp(upgrade) => Err(Upgraded(upgrade))
+                            }
+                        }
+                    }
+                }
+
+                // We are the sole receiver; there cannot be a blocking
+                // receiver already.
+                _ => unreachable!()
+            }
+        }
+    }
+
+    // Returns whether the upgrade was completed. If the upgrade wasn't
+    // completed, then the port couldn't get sent to the other half (it will
+    // never receive it).
+    pub fn upgrade(&self, up: Receiver<T>) -> UpgradeResult {
+        unsafe {
+            let prev = match *self.upgrade.get() {
+                NothingSent => NothingSent,
+                SendUsed => SendUsed,
+                _ => panic!("upgrading again"),
+            };
+            ptr::write(self.upgrade.get(), GoUp(up));
+
+            match self.state.swap(DISCONNECTED, Ordering::SeqCst) {
+                // If the channel is empty or has data on it, then we're good to go.
+                // Senders will check the data before the upgrade (in case we
+                // plastered over the DATA state).
+                DATA | EMPTY => UpSuccess,
+
+                // If the other end is already disconnected, then we failed the
+                // upgrade. Be sure to trash the port we were given.
+                DISCONNECTED => { ptr::replace(self.upgrade.get(), prev); UpDisconnected }
+
+                // If someone's waiting, we gotta wake them up
+                ptr => UpWoke(SignalToken::cast_from_usize(ptr))
+            }
+        }
+    }
+
+    pub fn drop_chan(&self) {
+        match self.state.swap(DISCONNECTED, Ordering::SeqCst) {
+            DATA | DISCONNECTED | EMPTY => {}
+
+            // If someone's waiting, we gotta wake them up
+            ptr => unsafe {
+                SignalToken::cast_from_usize(ptr).signal();
+            }
+        }
+    }
+
+    pub fn drop_port(&self) {
+        match self.state.swap(DISCONNECTED, Ordering::SeqCst) {
+            // An empty channel has nothing to do, and a remotely disconnected
+            // channel also has nothing to do b/c we're about to run the drop
+            // glue
+            DISCONNECTED | EMPTY => {}
+
+            // There's data on the channel, so make sure we destroy it promptly.
+            // This is why not using an arc is a little difficult (need the box
+            // to stay valid while we take the data).
+            DATA => unsafe { (&mut *self.data.get()).take().unwrap(); },
+
+            // We're the only ones that can block on this port
+            _ => unreachable!()
+        }
+    }
+
+    ////////////////////////////////////////////////////////////////////////////
+    // select implementation
+    ////////////////////////////////////////////////////////////////////////////
+
+    // If Ok, the value is whether this port has data, if Err, then the upgraded
+    // port needs to be checked instead of this one.
+    pub fn can_recv(&self) -> Result<bool, Receiver<T>> {
+        unsafe {
+            match self.state.load(Ordering::SeqCst) {
+                EMPTY => Ok(false), // Welp, we tried
+                DATA => Ok(true),   // we have some un-acquired data
+                DISCONNECTED if (*self.data.get()).is_some() => Ok(true), // we have data
+                DISCONNECTED => {
+                    match ptr::replace(self.upgrade.get(), SendUsed) {
+                        // The other end sent us an upgrade, so we need to
+                        // propagate upwards whether the upgrade can receive
+                        // data
+                        GoUp(upgrade) => Err(upgrade),
+
+                        // If the other end disconnected without sending an
+                        // upgrade, then we have data to receive (the channel is
+                        // disconnected).
+                        up => { ptr::write(self.upgrade.get(), up); Ok(true) }
+                    }
+                }
+                _ => unreachable!(), // we're the "one blocker"
+            }
+        }
+    }
+
+    // Attempts to start selection on this port. This can either succeed, fail
+    // because there is data, or fail because there is an upgrade pending.
+    pub fn start_selection(&self, token: SignalToken) -> SelectionResult<T> {
+        unsafe {
+            let ptr = token.cast_to_usize();
+            match self.state.compare_and_swap(EMPTY, ptr, Ordering::SeqCst) {
+                EMPTY => SelSuccess,
+                DATA => {
+                    drop(SignalToken::cast_from_usize(ptr));
+                    SelCanceled
+                }
+                DISCONNECTED if (*self.data.get()).is_some() => {
+                    drop(SignalToken::cast_from_usize(ptr));
+                    SelCanceled
+                }
+                DISCONNECTED => {
+                    match ptr::replace(self.upgrade.get(), SendUsed) {
+                        // The other end sent us an upgrade, so we need to
+                        // propagate upwards whether the upgrade can receive
+                        // data
+                        GoUp(upgrade) => {
+                            SelUpgraded(SignalToken::cast_from_usize(ptr), upgrade)
+                        }
+
+                        // If the other end disconnected without sending an
+                        // upgrade, then we have data to receive (the channel is
+                        // disconnected).
+                        up => {
+                            ptr::write(self.upgrade.get(), up);
+                            drop(SignalToken::cast_from_usize(ptr));
+                            SelCanceled
+                        }
+                    }
+                }
+                _ => unreachable!(), // we're the "one blocker"
+            }
+        }
+    }
+
+    // Remove a previous selecting thread from this port. This ensures that the
+    // blocked thread will no longer be visible to any other threads.
+    //
+    // The return value indicates whether there's data on this port.
+    pub fn abort_selection(&self) -> Result<bool, Receiver<T>> {
+        let state = match self.state.load(Ordering::SeqCst) {
+            // Each of these states means that no further activity will happen
+            // with regard to abortion selection
+            s @ EMPTY |
+            s @ DATA |
+            s @ DISCONNECTED => s,
+
+            // If we've got a blocked thread, then use an atomic to gain ownership
+            // of it (may fail)
+            ptr => self.state.compare_and_swap(ptr, EMPTY, Ordering::SeqCst)
+        };
+
+        // Now that we've got ownership of our state, figure out what to do
+        // about it.
+        match state {
+            EMPTY => unreachable!(),
+            // our thread used for select was stolen
+            DATA => Ok(true),
+
+            // If the other end has hung up, then we have complete ownership
+            // of the port. First, check if there was data waiting for us. This
+            // is possible if the other end sent something and then hung up.
+            //
+            // We then need to check to see if there was an upgrade requested,
+            // and if so, the upgraded port needs to have its selection aborted.
+            DISCONNECTED => unsafe {
+                if (*self.data.get()).is_some() {
+                    Ok(true)
+                } else {
+                    match ptr::replace(self.upgrade.get(), SendUsed) {
+                        GoUp(port) => Err(port),
+                        _ => Ok(true),
+                    }
+                }
+            },
+
+            // We woke ourselves up from select.
+            ptr => unsafe {
+                drop(SignalToken::cast_from_usize(ptr));
+                Ok(false)
+            }
+        }
+    }
+}
+
+impl<T> Drop for Packet<T> {
+    fn drop(&mut self) {
+        assert_eq!(self.state.load(Ordering::SeqCst), DISCONNECTED);
+    }
+}

ctr-std/src/sync/mpsc/select.rs

@@ -0,0 +1,791 @@
+// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Selection over an array of receivers
+//!
+//! This module contains the implementation machinery necessary for selecting
+//! over a number of receivers. One large goal of this module is to provide an
+//! efficient interface to selecting over any receiver of any type.
+//!
+//! This is achieved through an architecture of a "receiver set" in which
+//! receivers are added to a set and then the entire set is waited on at once.
+//! The set can be waited on multiple times to prevent re-adding each receiver
+//! to the set.
+//!
+//! Usage of this module is currently encouraged to go through the use of the
+//! `select!` macro. This macro allows naturally binding of variables to the
+//! received values of receivers in a much more natural syntax then usage of the
+//! `Select` structure directly.
+//!
+//! # Examples
+//!
+//! ```rust
+//! #![feature(mpsc_select)]
+//!
+//! use std::sync::mpsc::channel;
+//!
+//! let (tx1, rx1) = channel();
+//! let (tx2, rx2) = channel();
+//!
+//! tx1.send(1).unwrap();
+//! tx2.send(2).unwrap();
+//!
+//! select! {
+//!     val = rx1.recv() => {
+//!         assert_eq!(val.unwrap(), 1);
+//!     },
+//!     val = rx2.recv() => {
+//!         assert_eq!(val.unwrap(), 2);
+//!     }
+//! }
+//! ```
+
+#![allow(dead_code)]
+#![unstable(feature = "mpsc_select",
+            reason = "This implementation, while likely sufficient, is unsafe and \
+                      likely to be error prone. At some point in the future this \
+                      module will likely be replaced, and it is currently \
+                      unknown how much API breakage that will cause. The ability \
+                      to select over a number of channels will remain forever, \
+                      but no guarantees beyond this are being made",
+            issue = "27800")]
+
+
+use fmt;
+
+use core::cell::{Cell, UnsafeCell};
+use core::marker;
+use core::ptr;
+use core::usize;
+
+use sync::mpsc::{Receiver, RecvError};
+use sync::mpsc::blocking::{self, SignalToken};
+
+/// The "receiver set" of the select interface. This structure is used to manage
+/// a set of receivers which are being selected over.
+pub struct Select {
+    inner: UnsafeCell<SelectInner>,
+    next_id: Cell<usize>,
+}
+
+struct SelectInner {
+    head: *mut Handle<'static, ()>,
+    tail: *mut Handle<'static, ()>,
+}
+
+impl !marker::Send for Select {}
+
+/// A handle to a receiver which is currently a member of a `Select` set of
+/// receivers.  This handle is used to keep the receiver in the set as well as
+/// interact with the underlying receiver.
+pub struct Handle<'rx, T:Send+'rx> {
+    /// The ID of this handle, used to compare against the return value of
+    /// `Select::wait()`
+    id: usize,
+    selector: *mut SelectInner,
+    next: *mut Handle<'static, ()>,
+    prev: *mut Handle<'static, ()>,
+    added: bool,
+    packet: &'rx (Packet+'rx),
+
+    // due to our fun transmutes, we be sure to place this at the end. (nothing
+    // previous relies on T)
+    rx: &'rx Receiver<T>,
+}
+
+struct Packets { cur: *mut Handle<'static, ()> }
+
+#[doc(hidden)]
+#[derive(PartialEq, Eq)]
+pub enum StartResult {
+    Installed,
+    Abort,
+}
+
+#[doc(hidden)]
+pub trait Packet {
+    fn can_recv(&self) -> bool;
+    fn start_selection(&self, token: SignalToken) -> StartResult;
+    fn abort_selection(&self) -> bool;
+}
+
+impl Select {
+    /// Creates a new selection structure. This set is initially empty.
+    ///
+    /// Usage of this struct directly can sometimes be burdensome, and usage is much easier through
+    /// the `select!` macro.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(mpsc_select)]
+    ///
+    /// use std::sync::mpsc::Select;
+    ///
+    /// let select = Select::new();
+    /// ```
+    pub fn new() -> Select {
+        Select {
+            inner: UnsafeCell::new(SelectInner {
+                head: ptr::null_mut(),
+                tail: ptr::null_mut(),
+            }),
+            next_id: Cell::new(1),
+        }
+    }
+
+    /// Creates a new handle into this receiver set for a new receiver. Note
+    /// that this does *not* add the receiver to the receiver set, for that you
+    /// must call the `add` method on the handle itself.
+    pub fn handle<'a, T: Send>(&'a self, rx: &'a Receiver<T>) -> Handle<'a, T> {
+        let id = self.next_id.get();
+        self.next_id.set(id + 1);
+        Handle {
+            id: id,
+            selector: self.inner.get(),
+            next: ptr::null_mut(),
+            prev: ptr::null_mut(),
+            added: false,
+            rx: rx,
+            packet: rx,
+        }
+    }
+
+    /// Waits for an event on this receiver set. The returned value is *not* an
+    /// index, but rather an id. This id can be queried against any active
+    /// `Handle` structures (each one has an `id` method). The handle with
+    /// the matching `id` will have some sort of event available on it. The
+    /// event could either be that data is available or the corresponding
+    /// channel has been closed.
+    pub fn wait(&self) -> usize {
+        self.wait2(true)
+    }
+
+    /// Helper method for skipping the preflight checks during testing
+    fn wait2(&self, do_preflight_checks: bool) -> usize {
+        // Note that this is currently an inefficient implementation. We in
+        // theory have knowledge about all receivers in the set ahead of time,
+        // so this method shouldn't really have to iterate over all of them yet
+        // again. The idea with this "receiver set" interface is to get the
+        // interface right this time around, and later this implementation can
+        // be optimized.
+        //
+        // This implementation can be summarized by:
+        //
+        //      fn select(receivers) {
+        //          if any receiver ready { return ready index }
+        //          deschedule {
+        //              block on all receivers
+        //          }
+        //          unblock on all receivers
+        //          return ready index
+        //      }
+        //
+        // Most notably, the iterations over all of the receivers shouldn't be
+        // necessary.
+        unsafe {
+            // Stage 1: preflight checks. Look for any packets ready to receive
+            if do_preflight_checks {
+                for handle in self.iter() {
+                    if (*handle).packet.can_recv() {
+                        return (*handle).id();
+                    }
+                }
+            }
+
+            // Stage 2: begin the blocking process
+            //
+            // Create a number of signal tokens, and install each one
+            // sequentially until one fails. If one fails, then abort the
+            // selection on the already-installed tokens.
+            let (wait_token, signal_token) = blocking::tokens();
+            for (i, handle) in self.iter().enumerate() {
+                match (*handle).packet.start_selection(signal_token.clone()) {
+                    StartResult::Installed => {}
+                    StartResult::Abort => {
+                        // Go back and abort the already-begun selections
+                        for handle in self.iter().take(i) {
+                            (*handle).packet.abort_selection();
+                        }
+                        return (*handle).id;
+                    }
+                }
+            }
+
+            // Stage 3: no messages available, actually block
+            wait_token.wait();
+
+            // Stage 4: there *must* be message available; find it.
+            //
+            // Abort the selection process on each receiver. If the abort
+            // process returns `true`, then that means that the receiver is
+            // ready to receive some data. Note that this also means that the
+            // receiver may have yet to have fully read the `to_wake` field and
+            // woken us up (although the wakeup is guaranteed to fail).
+            //
+            // This situation happens in the window of where a sender invokes
+            // increment(), sees -1, and then decides to wake up the thread. After
+            // all this is done, the sending thread will set `selecting` to
+            // `false`. Until this is done, we cannot return. If we were to
+            // return, then a sender could wake up a receiver which has gone
+            // back to sleep after this call to `select`.
+            //
+            // Note that it is a "fairly small window" in which an increment()
+            // views that it should wake a thread up until the `selecting` bit
+            // is set to false. For now, the implementation currently just spins
+            // in a yield loop. This is very distasteful, but this
+            // implementation is already nowhere near what it should ideally be.
+            // A rewrite should focus on avoiding a yield loop, and for now this
+            // implementation is tying us over to a more efficient "don't
+            // iterate over everything every time" implementation.
+            let mut ready_id = usize::MAX;
+            for handle in self.iter() {
+                if (*handle).packet.abort_selection() {
+                    ready_id = (*handle).id;
+                }
+            }
+
+            // We must have found a ready receiver
+            assert!(ready_id != usize::MAX);
+            return ready_id;
+        }
+    }
+
+    fn iter(&self) -> Packets { Packets { cur: unsafe { &*self.inner.get() }.head } }
+}
+
+impl<'rx, T: Send> Handle<'rx, T> {
+    /// Retrieves the id of this handle.
+    #[inline]
+    pub fn id(&self) -> usize { self.id }
+
+    /// Blocks to receive a value on the underlying receiver, returning `Some` on
+    /// success or `None` if the channel disconnects. This function has the same
+    /// semantics as `Receiver.recv`
+    pub fn recv(&mut self) -> Result<T, RecvError> { self.rx.recv() }
+
+    /// Adds this handle to the receiver set that the handle was created from. This
+    /// method can be called multiple times, but it has no effect if `add` was
+    /// called previously.
+    ///
+    /// This method is unsafe because it requires that the `Handle` is not moved
+    /// while it is added to the `Select` set.
+    pub unsafe fn add(&mut self) {
+        if self.added { return }
+        let selector = &mut *self.selector;
+        let me = self as *mut Handle<'rx, T> as *mut Handle<'static, ()>;
+
+        if selector.head.is_null() {
+            selector.head = me;
+            selector.tail = me;
+        } else {
+            (*me).prev = selector.tail;
+            assert!((*me).next.is_null());
+            (*selector.tail).next = me;
+            selector.tail = me;
+        }
+        self.added = true;
+    }
+
+    /// Removes this handle from the `Select` set. This method is unsafe because
+    /// it has no guarantee that the `Handle` was not moved since `add` was
+    /// called.
+    pub unsafe fn remove(&mut self) {
+        if !self.added { return }
+
+        let selector = &mut *self.selector;
+        let me = self as *mut Handle<'rx, T> as *mut Handle<'static, ()>;
+
+        if self.prev.is_null() {
+            assert_eq!(selector.head, me);
+            selector.head = self.next;
+        } else {
+            (*self.prev).next = self.next;
+        }
+        if self.next.is_null() {
+            assert_eq!(selector.tail, me);
+            selector.tail = self.prev;
+        } else {
+            (*self.next).prev = self.prev;
+        }
+
+        self.next = ptr::null_mut();
+        self.prev = ptr::null_mut();
+
+        self.added = false;
+    }
+}
+
+impl Drop for Select {
+    fn drop(&mut self) {
+        unsafe {
+            assert!((&*self.inner.get()).head.is_null());
+            assert!((&*self.inner.get()).tail.is_null());
+        }
+    }
+}
+
+impl<'rx, T: Send> Drop for Handle<'rx, T> {
+    fn drop(&mut self) {
+        unsafe { self.remove() }
+    }
+}
+
+impl Iterator for Packets {
+    type Item = *mut Handle<'static, ()>;
+
+    fn next(&mut self) -> Option<*mut Handle<'static, ()>> {
+        if self.cur.is_null() {
+            None
+        } else {
+            let ret = Some(self.cur);
+            unsafe { self.cur = (*self.cur).next; }
+            ret
+        }
+    }
+}
+
+impl fmt::Debug for Select {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Select {{ .. }}")
+    }
+}
+
+impl<'rx, T:Send+'rx> fmt::Debug for Handle<'rx, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Handle {{ .. }}")
+    }
+}
+
+#[allow(unused_imports)]
+#[cfg(all(test, not(target_os = "emscripten")))]
+mod tests {
+    use thread;
+    use sync::mpsc::*;
+
+    // Don't use the libstd version so we can pull in the right Select structure
+    // (std::comm points at the wrong one)
+    macro_rules! select {
+        (
+            $($name:pat = $rx:ident.$meth:ident() => $code:expr),+
+        ) => ({
+            let sel = Select::new();
+            $( let mut $rx = sel.handle(&$rx); )+
+            unsafe {
+                $( $rx.add(); )+
+            }
+            let ret = sel.wait();
+            $( if ret == $rx.id() { let $name = $rx.$meth(); $code } else )+
+            { unreachable!() }
+        })
+    }
+
+    #[test]
+    fn smoke() {
+        let (tx1, rx1) = channel::<i32>();
+        let (tx2, rx2) = channel::<i32>();
+        tx1.send(1).unwrap();
+        select! {
+            foo = rx1.recv() => { assert_eq!(foo.unwrap(), 1); },
+            _bar = rx2.recv() => { panic!() }
+        }
+        tx2.send(2).unwrap();
+        select! {
+            _foo = rx1.recv() => { panic!() },
+            bar = rx2.recv() => { assert_eq!(bar.unwrap(), 2) }
+        }
+        drop(tx1);
+        select! {
+            foo = rx1.recv() => { assert!(foo.is_err()); },
+            _bar = rx2.recv() => { panic!() }
+        }
+        drop(tx2);
+        select! {
+            bar = rx2.recv() => { assert!(bar.is_err()); }
+        }
+    }
+
+    #[test]
+    fn smoke2() {
+        let (_tx1, rx1) = channel::<i32>();
+        let (_tx2, rx2) = channel::<i32>();
+        let (_tx3, rx3) = channel::<i32>();
+        let (_tx4, rx4) = channel::<i32>();
+        let (tx5, rx5) = channel::<i32>();
+        tx5.send(4).unwrap();
+        select! {
+            _foo = rx1.recv() => { panic!("1") },
+            _foo = rx2.recv() => { panic!("2") },
+            _foo = rx3.recv() => { panic!("3") },
+            _foo = rx4.recv() => { panic!("4") },
+            foo = rx5.recv() => { assert_eq!(foo.unwrap(), 4); }
+        }
+    }
+
+    #[test]
+    fn closed() {
+        let (_tx1, rx1) = channel::<i32>();
+        let (tx2, rx2) = channel::<i32>();
+        drop(tx2);
+
+        select! {
+            _a1 = rx1.recv() => { panic!() },
+            a2 = rx2.recv() => { assert!(a2.is_err()); }
+        }
+    }
+
+    #[test]
+    fn unblocks() {
+        let (tx1, rx1) = channel::<i32>();
+        let (_tx2, rx2) = channel::<i32>();
+        let (tx3, rx3) = channel::<i32>();
+
+        let _t = thread::spawn(move|| {
+            for _ in 0..20 { thread::yield_now(); }
+            tx1.send(1).unwrap();
+            rx3.recv().unwrap();
+            for _ in 0..20 { thread::yield_now(); }
+        });
+
+        select! {
+            a = rx1.recv() => { assert_eq!(a.unwrap(), 1); },
+            _b = rx2.recv() => { panic!() }
+        }
+        tx3.send(1).unwrap();
+        select! {
+            a = rx1.recv() => { assert!(a.is_err()) },
+            _b = rx2.recv() => { panic!() }
+        }
+    }
+
+    #[test]
+    fn both_ready() {
+        let (tx1, rx1) = channel::<i32>();
+        let (tx2, rx2) = channel::<i32>();
+        let (tx3, rx3) = channel::<()>();
+
+        let _t = thread::spawn(move|| {
+            for _ in 0..20 { thread::yield_now(); }
+            tx1.send(1).unwrap();
+            tx2.send(2).unwrap();
+            rx3.recv().unwrap();
+        });
+
+        select! {
+            a = rx1.recv() => { assert_eq!(a.unwrap(), 1); },
+            a = rx2.recv() => { assert_eq!(a.unwrap(), 2); }
+        }
+        select! {
+            a = rx1.recv() => { assert_eq!(a.unwrap(), 1); },
+            a = rx2.recv() => { assert_eq!(a.unwrap(), 2); }
+        }
+        assert_eq!(rx1.try_recv(), Err(TryRecvError::Empty));
+        assert_eq!(rx2.try_recv(), Err(TryRecvError::Empty));
+        tx3.send(()).unwrap();
+    }
+
+    #[test]
+    fn stress() {
+        const AMT: i32 = 10000;
+        let (tx1, rx1) = channel::<i32>();
+        let (tx2, rx2) = channel::<i32>();
+        let (tx3, rx3) = channel::<()>();
+
+        let _t = thread::spawn(move|| {
+            for i in 0..AMT {
+                if i % 2 == 0 {
+                    tx1.send(i).unwrap();
+                } else {
+                    tx2.send(i).unwrap();
+                }
+                rx3.recv().unwrap();
+            }
+        });
+
+        for i in 0..AMT {
+            select! {
+                i1 = rx1.recv() => { assert!(i % 2 == 0 && i == i1.unwrap()); },
+                i2 = rx2.recv() => { assert!(i % 2 == 1 && i == i2.unwrap()); }
+            }
+            tx3.send(()).unwrap();
+        }
+    }
+
+    #[test]
+    fn cloning() {
+        let (tx1, rx1) = channel::<i32>();
+        let (_tx2, rx2) = channel::<i32>();
+        let (tx3, rx3) = channel::<()>();
+
+        let _t = thread::spawn(move|| {
+            rx3.recv().unwrap();
+            tx1.clone();
+            assert_eq!(rx3.try_recv(), Err(TryRecvError::Empty));
+            tx1.send(2).unwrap();
+            rx3.recv().unwrap();
+        });
+
+        tx3.send(()).unwrap();
+        select! {
+            _i1 = rx1.recv() => {},
+            _i2 = rx2.recv() => panic!()
+        }
+        tx3.send(()).unwrap();
+    }
+
+    #[test]
+    fn cloning2() {
+        let (tx1, rx1) = channel::<i32>();
+        let (_tx2, rx2) = channel::<i32>();
+        let (tx3, rx3) = channel::<()>();
+
+        let _t = thread::spawn(move|| {
+            rx3.recv().unwrap();
+            tx1.clone();
+            assert_eq!(rx3.try_recv(), Err(TryRecvError::Empty));
+            tx1.send(2).unwrap();
+            rx3.recv().unwrap();
+        });
+
+        tx3.send(()).unwrap();
+        select! {
+            _i1 = rx1.recv() => {},
+            _i2 = rx2.recv() => panic!()
+        }
+        tx3.send(()).unwrap();
+    }
+
+    #[test]
+    fn cloning3() {
+        let (tx1, rx1) = channel::<()>();
+        let (tx2, rx2) = channel::<()>();
+        let (tx3, rx3) = channel::<()>();
+        let _t = thread::spawn(move|| {
+            let s = Select::new();
+            let mut h1 = s.handle(&rx1);
+            let mut h2 = s.handle(&rx2);
+            unsafe { h2.add(); }
+            unsafe { h1.add(); }
+            assert_eq!(s.wait(), h2.id);
+            tx3.send(()).unwrap();
+        });
+
+        for _ in 0..1000 { thread::yield_now(); }
+        drop(tx1.clone());
+        tx2.send(()).unwrap();
+        rx3.recv().unwrap();
+    }
+
+    #[test]
+    fn preflight1() {
+        let (tx, rx) = channel();
+        tx.send(()).unwrap();
+        select! {
+            _n = rx.recv() => {}
+        }
+    }
+
+    #[test]
+    fn preflight2() {
+        let (tx, rx) = channel();
+        tx.send(()).unwrap();
+        tx.send(()).unwrap();
+        select! {
+            _n = rx.recv() => {}
+        }
+    }
+
+    #[test]
+    fn preflight3() {
+        let (tx, rx) = channel();
+        drop(tx.clone());
+        tx.send(()).unwrap();
+        select! {
+            _n = rx.recv() => {}
+        }
+    }
+
+    #[test]
+    fn preflight4() {
+        let (tx, rx) = channel();
+        tx.send(()).unwrap();
+        let s = Select::new();
+        let mut h = s.handle(&rx);
+        unsafe { h.add(); }
+        assert_eq!(s.wait2(false), h.id);
+    }
+
+    #[test]
+    fn preflight5() {
+        let (tx, rx) = channel();
+        tx.send(()).unwrap();
+        tx.send(()).unwrap();
+        let s = Select::new();
+        let mut h = s.handle(&rx);
+        unsafe { h.add(); }
+        assert_eq!(s.wait2(false), h.id);
+    }
+
+    #[test]
+    fn preflight6() {
+        let (tx, rx) = channel();
+        drop(tx.clone());
+        tx.send(()).unwrap();
+        let s = Select::new();
+        let mut h = s.handle(&rx);
+        unsafe { h.add(); }
+        assert_eq!(s.wait2(false), h.id);
+    }
+
+    #[test]
+    fn preflight7() {
+        let (tx, rx) = channel::<()>();
+        drop(tx);
+        let s = Select::new();
+        let mut h = s.handle(&rx);
+        unsafe { h.add(); }
+        assert_eq!(s.wait2(false), h.id);
+    }
+
+    #[test]
+    fn preflight8() {
+        let (tx, rx) = channel();
+        tx.send(()).unwrap();
+        drop(tx);
+        rx.recv().unwrap();
+        let s = Select::new();
+        let mut h = s.handle(&rx);
+        unsafe { h.add(); }
+        assert_eq!(s.wait2(false), h.id);
+    }
+
+    #[test]
+    fn preflight9() {
+        let (tx, rx) = channel();
+        drop(tx.clone());
+        tx.send(()).unwrap();
+        drop(tx);
+        rx.recv().unwrap();
+        let s = Select::new();
+        let mut h = s.handle(&rx);
+        unsafe { h.add(); }
+        assert_eq!(s.wait2(false), h.id);
+    }
+
+    #[test]
+    fn oneshot_data_waiting() {
+        let (tx1, rx1) = channel();
+        let (tx2, rx2) = channel();
+        let _t = thread::spawn(move|| {
+            select! {
+                _n = rx1.recv() => {}
+            }
+            tx2.send(()).unwrap();
+        });
+
+        for _ in 0..100 { thread::yield_now() }
+        tx1.send(()).unwrap();
+        rx2.recv().unwrap();
+    }
+
+    #[test]
+    fn stream_data_waiting() {
+        let (tx1, rx1) = channel();
+        let (tx2, rx2) = channel();
+        tx1.send(()).unwrap();
+        tx1.send(()).unwrap();
+        rx1.recv().unwrap();
+        rx1.recv().unwrap();
+        let _t = thread::spawn(move|| {
+            select! {
+                _n = rx1.recv() => {}
+            }
+            tx2.send(()).unwrap();
+        });
+
+        for _ in 0..100 { thread::yield_now() }
+        tx1.send(()).unwrap();
+        rx2.recv().unwrap();
+    }
+
+    #[test]
+    fn shared_data_waiting() {
+        let (tx1, rx1) = channel();
+        let (tx2, rx2) = channel();
+        drop(tx1.clone());
+        tx1.send(()).unwrap();
+        rx1.recv().unwrap();
+        let _t = thread::spawn(move|| {
+            select! {
+                _n = rx1.recv() => {}
+            }
+            tx2.send(()).unwrap();
+        });
+
+        for _ in 0..100 { thread::yield_now() }
+        tx1.send(()).unwrap();
+        rx2.recv().unwrap();
+    }
+
+    #[test]
+    fn sync1() {
+        let (tx, rx) = sync_channel::<i32>(1);
+        tx.send(1).unwrap();
+        select! {
+            n = rx.recv() => { assert_eq!(n.unwrap(), 1); }
+        }
+    }
+
+    #[test]
+    fn sync2() {
+        let (tx, rx) = sync_channel::<i32>(0);
+        let _t = thread::spawn(move|| {
+            for _ in 0..100 { thread::yield_now() }
+            tx.send(1).unwrap();
+        });
+        select! {
+            n = rx.recv() => { assert_eq!(n.unwrap(), 1); }
+        }
+    }
+
+    #[test]
+    fn sync3() {
+        let (tx1, rx1) = sync_channel::<i32>(0);
+        let (tx2, rx2): (Sender<i32>, Receiver<i32>) = channel();
+        let _t = thread::spawn(move|| { tx1.send(1).unwrap(); });
+        let _t = thread::spawn(move|| { tx2.send(2).unwrap(); });
+        select! {
+            n = rx1.recv() => {
+                let n = n.unwrap();
+                assert_eq!(n, 1);
+                assert_eq!(rx2.recv().unwrap(), 2);
+            },
+            n = rx2.recv() => {
+                let n = n.unwrap();
+                assert_eq!(n, 2);
+                assert_eq!(rx1.recv().unwrap(), 1);
+            }
+        }
+    }
+
+    #[test]
+    fn fmt_debug_select() {
+        let sel = Select::new();
+        assert_eq!(format!("{:?}", sel), "Select { .. }");
+    }
+
+    #[test]
+    fn fmt_debug_handle() {
+        let (_, rx) = channel::<i32>();
+        let sel = Select::new();
+        let handle = sel.handle(&rx);
+        assert_eq!(format!("{:?}", handle), "Handle { .. }");
+    }
+}

ctr-std/src/sync/mpsc/shared.rs

@@ -0,0 +1,506 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/// Shared channels
+///
+/// This is the flavor of channels which are not necessarily optimized for any
+/// particular use case, but are the most general in how they are used. Shared
+/// channels are cloneable allowing for multiple senders.
+///
+/// High level implementation details can be found in the comment of the parent
+/// module. You'll also note that the implementation of the shared and stream
+/// channels are quite similar, and this is no coincidence!
+
+pub use self::Failure::*;
+
+use core::cmp;
+use core::intrinsics::abort;
+use core::isize;
+
+use cell::UnsafeCell;
+use ptr;
+use sync::atomic::{AtomicUsize, AtomicIsize, AtomicBool, Ordering};
+use sync::mpsc::blocking::{self, SignalToken};
+use sync::mpsc::mpsc_queue as mpsc;
+use sync::mpsc::select::StartResult::*;
+use sync::mpsc::select::StartResult;
+use sync::{Mutex, MutexGuard};
+use thread;
+use time::Instant;
+
+const DISCONNECTED: isize = isize::MIN;
+const FUDGE: isize = 1024;
+const MAX_REFCOUNT: usize = (isize::MAX) as usize;
+#[cfg(test)]
+const MAX_STEALS: isize = 5;
+#[cfg(not(test))]
+const MAX_STEALS: isize = 1 << 20;
+
+pub struct Packet<T> {
+    queue: mpsc::Queue<T>,
+    cnt: AtomicIsize, // How many items are on this channel
+    steals: UnsafeCell<isize>, // How many times has a port received without blocking?
+    to_wake: AtomicUsize, // SignalToken for wake up
+
+    // The number of channels which are currently using this packet.
+    channels: AtomicUsize,
+
+    // See the discussion in Port::drop and the channel send methods for what
+    // these are used for
+    port_dropped: AtomicBool,
+    sender_drain: AtomicIsize,
+
+    // this lock protects various portions of this implementation during
+    // select()
+    select_lock: Mutex<()>,
+}
+
+pub enum Failure {
+    Empty,
+    Disconnected,
+}
+
+impl<T> Packet<T> {
+    // Creation of a packet *must* be followed by a call to postinit_lock
+    // and later by inherit_blocker
+    pub fn new() -> Packet<T> {
+        Packet {
+            queue: mpsc::Queue::new(),
+            cnt: AtomicIsize::new(0),
+            steals: UnsafeCell::new(0),
+            to_wake: AtomicUsize::new(0),
+            channels: AtomicUsize::new(2),
+            port_dropped: AtomicBool::new(false),
+            sender_drain: AtomicIsize::new(0),
+            select_lock: Mutex::new(()),
+        }
+    }
+
+    // This function should be used after newly created Packet
+    // was wrapped with an Arc
+    // In other case mutex data will be duplicated while cloning
+    // and that could cause problems on platforms where it is
+    // represented by opaque data structure
+    pub fn postinit_lock(&self) -> MutexGuard<()> {
+        self.select_lock.lock().unwrap()
+    }
+
+    // This function is used at the creation of a shared packet to inherit a
+    // previously blocked thread. This is done to prevent spurious wakeups of
+    // threads in select().
+    //
+    // This can only be called at channel-creation time
+    pub fn inherit_blocker(&self,
+                           token: Option<SignalToken>,
+                           guard: MutexGuard<()>) {
+        token.map(|token| {
+            assert_eq!(self.cnt.load(Ordering::SeqCst), 0);
+            assert_eq!(self.to_wake.load(Ordering::SeqCst), 0);
+            self.to_wake.store(unsafe { token.cast_to_usize() }, Ordering::SeqCst);
+            self.cnt.store(-1, Ordering::SeqCst);
+
+            // This store is a little sketchy. What's happening here is that
+            // we're transferring a blocker from a oneshot or stream channel to
+            // this shared channel. In doing so, we never spuriously wake them
+            // up and rather only wake them up at the appropriate time. This
+            // implementation of shared channels assumes that any blocking
+            // recv() will undo the increment of steals performed in try_recv()
+            // once the recv is complete.  This thread that we're inheriting,
+            // however, is not in the middle of recv. Hence, the first time we
+            // wake them up, they're going to wake up from their old port, move
+            // on to the upgraded port, and then call the block recv() function.
+            //
+            // When calling this function, they'll find there's data immediately
+            // available, counting it as a steal. This in fact wasn't a steal
+            // because we appropriately blocked them waiting for data.
+            //
+            // To offset this bad increment, we initially set the steal count to
+            // -1. You'll find some special code in abort_selection() as well to
+            // ensure that this -1 steal count doesn't escape too far.
+            unsafe { *self.steals.get() = -1; }
+        });
+
+        // When the shared packet is constructed, we grabbed this lock. The
+        // purpose of this lock is to ensure that abort_selection() doesn't
+        // interfere with this method. After we unlock this lock, we're
+        // signifying that we're done modifying self.cnt and self.to_wake and
+        // the port is ready for the world to continue using it.
+        drop(guard);
+    }
+
+    pub fn send(&self, t: T) -> Result<(), T> {
+        // See Port::drop for what's going on
+        if self.port_dropped.load(Ordering::SeqCst) { return Err(t) }
+
+        // Note that the multiple sender case is a little trickier
+        // semantically than the single sender case. The logic for
+        // incrementing is "add and if disconnected store disconnected".
+        // This could end up leading some senders to believe that there
+        // wasn't a disconnect if in fact there was a disconnect. This means
+        // that while one thread is attempting to re-store the disconnected
+        // states, other threads could walk through merrily incrementing
+        // this very-negative disconnected count. To prevent senders from
+        // spuriously attempting to send when the channels is actually
+        // disconnected, the count has a ranged check here.
+        //
+        // This is also done for another reason. Remember that the return
+        // value of this function is:
+        //
+        //  `true` == the data *may* be received, this essentially has no
+        //            meaning
+        //  `false` == the data will *never* be received, this has a lot of
+        //             meaning
+        //
+        // In the SPSC case, we have a check of 'queue.is_empty()' to see
+        // whether the data was actually received, but this same condition
+        // means nothing in a multi-producer context. As a result, this
+        // preflight check serves as the definitive "this will never be
+        // received". Once we get beyond this check, we have permanently
+        // entered the realm of "this may be received"
+        if self.cnt.load(Ordering::SeqCst) < DISCONNECTED + FUDGE {
+            return Err(t)
+        }
+
+        self.queue.push(t);
+        match self.cnt.fetch_add(1, Ordering::SeqCst) {
+            -1 => {
+                self.take_to_wake().signal();
+            }
+
+            // In this case, we have possibly failed to send our data, and
+            // we need to consider re-popping the data in order to fully
+            // destroy it. We must arbitrate among the multiple senders,
+            // however, because the queues that we're using are
+            // single-consumer queues. In order to do this, all exiting
+            // pushers will use an atomic count in order to count those
+            // flowing through. Pushers who see 0 are required to drain as
+            // much as possible, and then can only exit when they are the
+            // only pusher (otherwise they must try again).
+            n if n < DISCONNECTED + FUDGE => {
+                // see the comment in 'try' for a shared channel for why this
+                // window of "not disconnected" is ok.
+                self.cnt.store(DISCONNECTED, Ordering::SeqCst);
+
+                if self.sender_drain.fetch_add(1, Ordering::SeqCst) == 0 {
+                    loop {
+                        // drain the queue, for info on the thread yield see the
+                        // discussion in try_recv
+                        loop {
+                            match self.queue.pop() {
+                                mpsc::Data(..) => {}
+                                mpsc::Empty => break,
+                                mpsc::Inconsistent => thread::yield_now(),
+                            }
+                        }
+                        // maybe we're done, if we're not the last ones
+                        // here, then we need to go try again.
+                        if self.sender_drain.fetch_sub(1, Ordering::SeqCst) == 1 {
+                            break
+                        }
+                    }
+
+                    // At this point, there may still be data on the queue,
+                    // but only if the count hasn't been incremented and
+                    // some other sender hasn't finished pushing data just
+                    // yet. That sender in question will drain its own data.
+                }
+            }
+
+            // Can't make any assumptions about this case like in the SPSC case.
+            _ => {}
+        }
+
+        Ok(())
+    }
+
+    pub fn recv(&self, deadline: Option<Instant>) -> Result<T, Failure> {
+        // This code is essentially the exact same as that found in the stream
+        // case (see stream.rs)
+        match self.try_recv() {
+            Err(Empty) => {}
+            data => return data,
+        }
+
+        let (wait_token, signal_token) = blocking::tokens();
+        if self.decrement(signal_token) == Installed {
+            if let Some(deadline) = deadline {
+                let timed_out = !wait_token.wait_max_until(deadline);
+                if timed_out {
+                    self.abort_selection(false);
+                }
+            } else {
+                wait_token.wait();
+            }
+        }
+
+        match self.try_recv() {
+            data @ Ok(..) => unsafe { *self.steals.get() -= 1; data },
+            data => data,
+        }
+    }
+
+    // Essentially the exact same thing as the stream decrement function.
+    // Returns true if blocking should proceed.
+    fn decrement(&self, token: SignalToken) -> StartResult {
+        unsafe {
+            assert_eq!(self.to_wake.load(Ordering::SeqCst), 0);
+            let ptr = token.cast_to_usize();
+            self.to_wake.store(ptr, Ordering::SeqCst);
+
+            let steals = ptr::replace(self.steals.get(), 0);
+
+            match self.cnt.fetch_sub(1 + steals, Ordering::SeqCst) {
+                DISCONNECTED => { self.cnt.store(DISCONNECTED, Ordering::SeqCst); }
+                // If we factor in our steals and notice that the channel has no
+                // data, we successfully sleep
+                n => {
+                    assert!(n >= 0);
+                    if n - steals <= 0 { return Installed }
+                }
+            }
+
+            self.to_wake.store(0, Ordering::SeqCst);
+            drop(SignalToken::cast_from_usize(ptr));
+            Abort
+        }
+    }
+
+    pub fn try_recv(&self) -> Result<T, Failure> {
+        let ret = match self.queue.pop() {
+            mpsc::Data(t) => Some(t),
+            mpsc::Empty => None,
+
+            // This is a bit of an interesting case. The channel is reported as
+            // having data available, but our pop() has failed due to the queue
+            // being in an inconsistent state.  This means that there is some
+            // pusher somewhere which has yet to complete, but we are guaranteed
+            // that a pop will eventually succeed. In this case, we spin in a
+            // yield loop because the remote sender should finish their enqueue
+            // operation "very quickly".
+            //
+            // Avoiding this yield loop would require a different queue
+            // abstraction which provides the guarantee that after M pushes have
+            // succeeded, at least M pops will succeed. The current queues
+            // guarantee that if there are N active pushes, you can pop N times
+            // once all N have finished.
+            mpsc::Inconsistent => {
+                let data;
+                loop {
+                    thread::yield_now();
+                    match self.queue.pop() {
+                        mpsc::Data(t) => { data = t; break }
+                        mpsc::Empty => panic!("inconsistent => empty"),
+                        mpsc::Inconsistent => {}
+                    }
+                }
+                Some(data)
+            }
+        };
+        match ret {
+            // See the discussion in the stream implementation for why we
+            // might decrement steals.
+            Some(data) => unsafe {
+                if *self.steals.get() > MAX_STEALS {
+                    match self.cnt.swap(0, Ordering::SeqCst) {
+                        DISCONNECTED => {
+                            self.cnt.store(DISCONNECTED, Ordering::SeqCst);
+                        }
+                        n => {
+                            let m = cmp::min(n, *self.steals.get());
+                            *self.steals.get() -= m;
+                            self.bump(n - m);
+                        }
+                    }
+                    assert!(*self.steals.get() >= 0);
+                }
+                *self.steals.get() += 1;
+                Ok(data)
+            },
+
+            // See the discussion in the stream implementation for why we try
+            // again.
+            None => {
+                match self.cnt.load(Ordering::SeqCst) {
+                    n if n != DISCONNECTED => Err(Empty),
+                    _ => {
+                        match self.queue.pop() {
+                            mpsc::Data(t) => Ok(t),
+                            mpsc::Empty => Err(Disconnected),
+                            // with no senders, an inconsistency is impossible.
+                            mpsc::Inconsistent => unreachable!(),
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    // Prepares this shared packet for a channel clone, essentially just bumping
+    // a refcount.
+    pub fn clone_chan(&self) {
+        let old_count = self.channels.fetch_add(1, Ordering::SeqCst);
+
+        // See comments on Arc::clone() on why we do this (for `mem::forget`).
+        if old_count > MAX_REFCOUNT {
+            unsafe {
+                abort();
+            }
+        }
+    }
+
+    // Decrement the reference count on a channel. This is called whenever a
+    // Chan is dropped and may end up waking up a receiver. It's the receiver's
+    // responsibility on the other end to figure out that we've disconnected.
+    pub fn drop_chan(&self) {
+        match self.channels.fetch_sub(1, Ordering::SeqCst) {
+            1 => {}
+            n if n > 1 => return,
+            n => panic!("bad number of channels left {}", n),
+        }
+
+        match self.cnt.swap(DISCONNECTED, Ordering::SeqCst) {
+            -1 => { self.take_to_wake().signal(); }
+            DISCONNECTED => {}
+            n => { assert!(n >= 0); }
+        }
+    }
+
+    // See the long discussion inside of stream.rs for why the queue is drained,
+    // and why it is done in this fashion.
+    pub fn drop_port(&self) {
+        self.port_dropped.store(true, Ordering::SeqCst);
+        let mut steals = unsafe { *self.steals.get() };
+        while {
+            let cnt = self.cnt.compare_and_swap(steals, DISCONNECTED, Ordering::SeqCst);
+            cnt != DISCONNECTED && cnt != steals
+        } {
+            // See the discussion in 'try_recv' for why we yield
+            // control of this thread.
+            loop {
+                match self.queue.pop() {
+                    mpsc::Data(..) => { steals += 1; }
+                    mpsc::Empty | mpsc::Inconsistent => break,
+                }
+            }
+        }
+    }
+
+    // Consumes ownership of the 'to_wake' field.
+    fn take_to_wake(&self) -> SignalToken {
+        let ptr = self.to_wake.load(Ordering::SeqCst);
+        self.to_wake.store(0, Ordering::SeqCst);
+        assert!(ptr != 0);
+        unsafe { SignalToken::cast_from_usize(ptr) }
+    }
+
+    ////////////////////////////////////////////////////////////////////////////
+    // select implementation
+    ////////////////////////////////////////////////////////////////////////////
+
+    // Helper function for select, tests whether this port can receive without
+    // blocking (obviously not an atomic decision).
+    //
+    // This is different than the stream version because there's no need to peek
+    // at the queue, we can just look at the local count.
+    pub fn can_recv(&self) -> bool {
+        let cnt = self.cnt.load(Ordering::SeqCst);
+        cnt == DISCONNECTED || cnt - unsafe { *self.steals.get() } > 0
+    }
+
+    // increment the count on the channel (used for selection)
+    fn bump(&self, amt: isize) -> isize {
+        match self.cnt.fetch_add(amt, Ordering::SeqCst) {
+            DISCONNECTED => {
+                self.cnt.store(DISCONNECTED, Ordering::SeqCst);
+                DISCONNECTED
+            }
+            n => n
+        }
+    }
+
+    // Inserts the signal token for selection on this port, returning true if
+    // blocking should proceed.
+    //
+    // The code here is the same as in stream.rs, except that it doesn't need to
+    // peek at the channel to see if an upgrade is pending.
+    pub fn start_selection(&self, token: SignalToken) -> StartResult {
+        match self.decrement(token) {
+            Installed => Installed,
+            Abort => {
+                let prev = self.bump(1);
+                assert!(prev == DISCONNECTED || prev >= 0);
+                Abort
+            }
+        }
+    }
+
+    // Cancels a previous thread waiting on this port, returning whether there's
+    // data on the port.
+    //
+    // This is similar to the stream implementation (hence fewer comments), but
+    // uses a different value for the "steals" variable.
+    pub fn abort_selection(&self, _was_upgrade: bool) -> bool {
+        // Before we do anything else, we bounce on this lock. The reason for
+        // doing this is to ensure that any upgrade-in-progress is gone and
+        // done with. Without this bounce, we can race with inherit_blocker
+        // about looking at and dealing with to_wake. Once we have acquired the
+        // lock, we are guaranteed that inherit_blocker is done.
+        {
+            let _guard = self.select_lock.lock().unwrap();
+        }
+
+        // Like the stream implementation, we want to make sure that the count
+        // on the channel goes non-negative. We don't know how negative the
+        // stream currently is, so instead of using a steal value of 1, we load
+        // the channel count and figure out what we should do to make it
+        // positive.
+        let steals = {
+            let cnt = self.cnt.load(Ordering::SeqCst);
+            if cnt < 0 && cnt != DISCONNECTED {-cnt} else {0}
+        };
+        let prev = self.bump(steals + 1);
+
+        if prev == DISCONNECTED {
+            assert_eq!(self.to_wake.load(Ordering::SeqCst), 0);
+            true
+        } else {
+            let cur = prev + steals + 1;
+            assert!(cur >= 0);
+            if prev < 0 {
+                drop(self.take_to_wake());
+            } else {
+                while self.to_wake.load(Ordering::SeqCst) != 0 {
+                    thread::yield_now();
+                }
+            }
+            unsafe {
+                // if the number of steals is -1, it was the pre-emptive -1 steal
+                // count from when we inherited a blocker. This is fine because
+                // we're just going to overwrite it with a real value.
+                let old = self.steals.get();
+                assert!(*old == 0 || *old == -1);
+                *old = steals;
+                prev >= 0
+            }
+        }
+    }
+}
+
+impl<T> Drop for Packet<T> {
+    fn drop(&mut self) {
+        // Note that this load is not only an assert for correctness about
+        // disconnection, but also a proper fence before the read of
+        // `to_wake`, so this assert cannot be removed with also removing
+        // the `to_wake` assert.
+        assert_eq!(self.cnt.load(Ordering::SeqCst), DISCONNECTED);
+        assert_eq!(self.to_wake.load(Ordering::SeqCst), 0);
+        assert_eq!(self.channels.load(Ordering::SeqCst), 0);
+    }
+}

ctr-std/src/sync/mpsc/spsc_queue.rs

@@ -0,0 +1,337 @@
+/* Copyright (c) 2010-2011 Dmitry Vyukov. All rights reserved.
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *    1. Redistributions of source code must retain the above copyright notice,
+ *       this list of conditions and the following disclaimer.
+ *
+ *    2. Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY DMITRY VYUKOV "AS IS" AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+ * SHALL DMITRY VYUKOV OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * The views and conclusions contained in the software and documentation are
+ * those of the authors and should not be interpreted as representing official
+ * policies, either expressed or implied, of Dmitry Vyukov.
+ */
+
+// http://www.1024cores.net/home/lock-free-algorithms/queues/unbounded-spsc-queue
+
+//! A single-producer single-consumer concurrent queue
+//!
+//! This module contains the implementation of an SPSC queue which can be used
+//! concurrently between two threads. This data structure is safe to use and
+//! enforces the semantics that there is one pusher and one popper.
+
+use alloc::boxed::Box;
+use core::ptr;
+use core::cell::UnsafeCell;
+
+use sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
+
+// Node within the linked list queue of messages to send
+struct Node<T> {
+    // FIXME: this could be an uninitialized T if we're careful enough, and
+    //      that would reduce memory usage (and be a bit faster).
+    //      is it worth it?
+    value: Option<T>,           // nullable for re-use of nodes
+    next: AtomicPtr<Node<T>>,   // next node in the queue
+}
+
+/// The single-producer single-consumer queue. This structure is not cloneable,
+/// but it can be safely shared in an Arc if it is guaranteed that there
+/// is only one popper and one pusher touching the queue at any one point in
+/// time.
+pub struct Queue<T> {
+    // consumer fields
+    tail: UnsafeCell<*mut Node<T>>, // where to pop from
+    tail_prev: AtomicPtr<Node<T>>, // where to pop from
+
+    // producer fields
+    head: UnsafeCell<*mut Node<T>>,      // where to push to
+    first: UnsafeCell<*mut Node<T>>,     // where to get new nodes from
+    tail_copy: UnsafeCell<*mut Node<T>>, // between first/tail
+
+    // Cache maintenance fields. Additions and subtractions are stored
+    // separately in order to allow them to use nonatomic addition/subtraction.
+    cache_bound: usize,
+    cache_additions: AtomicUsize,
+    cache_subtractions: AtomicUsize,
+}
+
+unsafe impl<T: Send> Send for Queue<T> { }
+
+unsafe impl<T: Send> Sync for Queue<T> { }
+
+impl<T> Node<T> {
+    fn new() -> *mut Node<T> {
+        Box::into_raw(box Node {
+            value: None,
+            next: AtomicPtr::new(ptr::null_mut::<Node<T>>()),
+        })
+    }
+}
+
+impl<T> Queue<T> {
+    /// Creates a new queue.
+    ///
+    /// This is unsafe as the type system doesn't enforce a single
+    /// consumer-producer relationship. It also allows the consumer to `pop`
+    /// items while there is a `peek` active due to all methods having a
+    /// non-mutable receiver.
+    ///
+    /// # Arguments
+    ///
+    ///   * `bound` - This queue implementation is implemented with a linked
+    ///               list, and this means that a push is always a malloc. In
+    ///               order to amortize this cost, an internal cache of nodes is
+    ///               maintained to prevent a malloc from always being
+    ///               necessary. This bound is the limit on the size of the
+    ///               cache (if desired). If the value is 0, then the cache has
+    ///               no bound. Otherwise, the cache will never grow larger than
+    ///               `bound` (although the queue itself could be much larger.
+    pub unsafe fn new(bound: usize) -> Queue<T> {
+        let n1 = Node::new();
+        let n2 = Node::new();
+        (*n1).next.store(n2, Ordering::Relaxed);
+        Queue {
+            tail: UnsafeCell::new(n2),
+            tail_prev: AtomicPtr::new(n1),
+            head: UnsafeCell::new(n2),
+            first: UnsafeCell::new(n1),
+            tail_copy: UnsafeCell::new(n1),
+            cache_bound: bound,
+            cache_additions: AtomicUsize::new(0),
+            cache_subtractions: AtomicUsize::new(0),
+        }
+    }
+
+    /// Pushes a new value onto this queue. Note that to use this function
+    /// safely, it must be externally guaranteed that there is only one pusher.
+    pub fn push(&self, t: T) {
+        unsafe {
+            // Acquire a node (which either uses a cached one or allocates a new
+            // one), and then append this to the 'head' node.
+            let n = self.alloc();
+            assert!((*n).value.is_none());
+            (*n).value = Some(t);
+            (*n).next.store(ptr::null_mut(), Ordering::Relaxed);
+            (**self.head.get()).next.store(n, Ordering::Release);
+            *self.head.get() = n;
+        }
+    }
+
+    unsafe fn alloc(&self) -> *mut Node<T> {
+        // First try to see if we can consume the 'first' node for our uses.
+        // We try to avoid as many atomic instructions as possible here, so
+        // the addition to cache_subtractions is not atomic (plus we're the
+        // only one subtracting from the cache).
+        if *self.first.get() != *self.tail_copy.get() {
+            if self.cache_bound > 0 {
+                let b = self.cache_subtractions.load(Ordering::Relaxed);
+                self.cache_subtractions.store(b + 1, Ordering::Relaxed);
+            }
+            let ret = *self.first.get();
+            *self.first.get() = (*ret).next.load(Ordering::Relaxed);
+            return ret;
+        }
+        // If the above fails, then update our copy of the tail and try
+        // again.
+        *self.tail_copy.get() = self.tail_prev.load(Ordering::Acquire);
+        if *self.first.get() != *self.tail_copy.get() {
+            if self.cache_bound > 0 {
+                let b = self.cache_subtractions.load(Ordering::Relaxed);
+                self.cache_subtractions.store(b + 1, Ordering::Relaxed);
+            }
+            let ret = *self.first.get();
+            *self.first.get() = (*ret).next.load(Ordering::Relaxed);
+            return ret;
+        }
+        // If all of that fails, then we have to allocate a new node
+        // (there's nothing in the node cache).
+        Node::new()
+    }
+
+    /// Attempts to pop a value from this queue. Remember that to use this type
+    /// safely you must ensure that there is only one popper at a time.
+    pub fn pop(&self) -> Option<T> {
+        unsafe {
+            // The `tail` node is not actually a used node, but rather a
+            // sentinel from where we should start popping from. Hence, look at
+            // tail's next field and see if we can use it. If we do a pop, then
+            // the current tail node is a candidate for going into the cache.
+            let tail = *self.tail.get();
+            let next = (*tail).next.load(Ordering::Acquire);
+            if next.is_null() { return None }
+            assert!((*next).value.is_some());
+            let ret = (*next).value.take();
+
+            *self.tail.get() = next;
+            if self.cache_bound == 0 {
+                self.tail_prev.store(tail, Ordering::Release);
+            } else {
+                // FIXME: this is dubious with overflow.
+                let additions = self.cache_additions.load(Ordering::Relaxed);
+                let subtractions = self.cache_subtractions.load(Ordering::Relaxed);
+                let size = additions - subtractions;
+
+                if size < self.cache_bound {
+                    self.tail_prev.store(tail, Ordering::Release);
+                    self.cache_additions.store(additions + 1, Ordering::Relaxed);
+                } else {
+                    (*self.tail_prev.load(Ordering::Relaxed))
+                          .next.store(next, Ordering::Relaxed);
+                    // We have successfully erased all references to 'tail', so
+                    // now we can safely drop it.
+                    let _: Box<Node<T>> = Box::from_raw(tail);
+                }
+            }
+            ret
+        }
+    }
+
+    /// Attempts to peek at the head of the queue, returning `None` if the queue
+    /// has no data currently
+    ///
+    /// # Warning
+    /// The reference returned is invalid if it is not used before the consumer
+    /// pops the value off the queue. If the producer then pushes another value
+    /// onto the queue, it will overwrite the value pointed to by the reference.
+    pub fn peek(&self) -> Option<&mut T> {
+        // This is essentially the same as above with all the popping bits
+        // stripped out.
+        unsafe {
+            let tail = *self.tail.get();
+            let next = (*tail).next.load(Ordering::Acquire);
+            if next.is_null() { None } else { (*next).value.as_mut() }
+        }
+    }
+}
+
+impl<T> Drop for Queue<T> {
+    fn drop(&mut self) {
+        unsafe {
+            let mut cur = *self.first.get();
+            while !cur.is_null() {
+                let next = (*cur).next.load(Ordering::Relaxed);
+                let _n: Box<Node<T>> = Box::from_raw(cur);
+                cur = next;
+            }
+        }
+    }
+}
+
+#[cfg(all(test, not(target_os = "emscripten")))]
+mod tests {
+    use sync::Arc;
+    use super::Queue;
+    use thread;
+    use sync::mpsc::channel;
+
+    #[test]
+    fn smoke() {
+        unsafe {
+            let queue = Queue::new(0);
+            queue.push(1);
+            queue.push(2);
+            assert_eq!(queue.pop(), Some(1));
+            assert_eq!(queue.pop(), Some(2));
+            assert_eq!(queue.pop(), None);
+            queue.push(3);
+            queue.push(4);
+            assert_eq!(queue.pop(), Some(3));
+            assert_eq!(queue.pop(), Some(4));
+            assert_eq!(queue.pop(), None);
+        }
+    }
+
+    #[test]
+    fn peek() {
+        unsafe {
+            let queue = Queue::new(0);
+            queue.push(vec![1]);
+
+            // Ensure the borrowchecker works
+            match queue.peek() {
+                Some(vec) => {
+                    assert_eq!(&*vec, &[1]);
+                },
+                None => unreachable!()
+            }
+
+            match queue.pop() {
+                Some(vec) => {
+                    assert_eq!(&*vec, &[1]);
+                },
+                None => unreachable!()
+            }
+        }
+    }
+
+    #[test]
+    fn drop_full() {
+        unsafe {
+            let q: Queue<Box<_>> = Queue::new(0);
+            q.push(box 1);
+            q.push(box 2);
+        }
+    }
+
+    #[test]
+    fn smoke_bound() {
+        unsafe {
+            let q = Queue::new(0);
+            q.push(1);
+            q.push(2);
+            assert_eq!(q.pop(), Some(1));
+            assert_eq!(q.pop(), Some(2));
+            assert_eq!(q.pop(), None);
+            q.push(3);
+            q.push(4);
+            assert_eq!(q.pop(), Some(3));
+            assert_eq!(q.pop(), Some(4));
+            assert_eq!(q.pop(), None);
+        }
+    }
+
+    #[test]
+    fn stress() {
+        unsafe {
+            stress_bound(0);
+            stress_bound(1);
+        }
+
+        unsafe fn stress_bound(bound: usize) {
+            let q = Arc::new(Queue::new(bound));
+
+            let (tx, rx) = channel();
+            let q2 = q.clone();
+            let _t = thread::spawn(move|| {
+                for _ in 0..100000 {
+                    loop {
+                        match q2.pop() {
+                            Some(1) => break,
+                            Some(_) => panic!(),
+                            None => {}
+                        }
+                    }
+                }
+                tx.send(()).unwrap();
+            });
+            for _ in 0..100000 {
+                q.push(1);
+            }
+            rx.recv().unwrap();
+        }
+    }
+}

ctr-std/src/sync/mpsc/stream.rs

@@ -0,0 +1,487 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/// Stream channels
+///
+/// This is the flavor of channels which are optimized for one sender and one
+/// receiver. The sender will be upgraded to a shared channel if the channel is
+/// cloned.
+///
+/// High level implementation details can be found in the comment of the parent
+/// module.
+
+pub use self::Failure::*;
+pub use self::UpgradeResult::*;
+pub use self::SelectionResult::*;
+use self::Message::*;
+
+use cell::UnsafeCell;
+use core::cmp;
+use core::isize;
+use ptr;
+use thread;
+use time::Instant;
+
+use sync::atomic::{AtomicIsize, AtomicUsize, Ordering, AtomicBool};
+use sync::mpsc::Receiver;
+use sync::mpsc::blocking::{self, SignalToken};
+use sync::mpsc::spsc_queue as spsc;
+
+const DISCONNECTED: isize = isize::MIN;
+#[cfg(test)]
+const MAX_STEALS: isize = 5;
+#[cfg(not(test))]
+const MAX_STEALS: isize = 1 << 20;
+
+pub struct Packet<T> {
+    queue: spsc::Queue<Message<T>>, // internal queue for all message
+
+    cnt: AtomicIsize, // How many items are on this channel
+    steals: UnsafeCell<isize>, // How many times has a port received without blocking?
+    to_wake: AtomicUsize, // SignalToken for the blocked thread to wake up
+
+    port_dropped: AtomicBool, // flag if the channel has been destroyed.
+}
+
+pub enum Failure<T> {
+    Empty,
+    Disconnected,
+    Upgraded(Receiver<T>),
+}
+
+pub enum UpgradeResult {
+    UpSuccess,
+    UpDisconnected,
+    UpWoke(SignalToken),
+}
+
+pub enum SelectionResult<T> {
+    SelSuccess,
+    SelCanceled,
+    SelUpgraded(SignalToken, Receiver<T>),
+}
+
+// Any message could contain an "upgrade request" to a new shared port, so the
+// internal queue it's a queue of T, but rather Message<T>
+enum Message<T> {
+    Data(T),
+    GoUp(Receiver<T>),
+}
+
+impl<T> Packet<T> {
+    pub fn new() -> Packet<T> {
+        Packet {
+            queue: unsafe { spsc::Queue::new(128) },
+
+            cnt: AtomicIsize::new(0),
+            steals: UnsafeCell::new(0),
+            to_wake: AtomicUsize::new(0),
+
+            port_dropped: AtomicBool::new(false),
+        }
+    }
+
+    pub fn send(&self, t: T) -> Result<(), T> {
+        // If the other port has deterministically gone away, then definitely
+        // must return the data back up the stack. Otherwise, the data is
+        // considered as being sent.
+        if self.port_dropped.load(Ordering::SeqCst) { return Err(t) }
+
+        match self.do_send(Data(t)) {
+            UpSuccess | UpDisconnected => {},
+            UpWoke(token) => { token.signal(); }
+        }
+        Ok(())
+    }
+
+    pub fn upgrade(&self, up: Receiver<T>) -> UpgradeResult {
+        // If the port has gone away, then there's no need to proceed any
+        // further.
+        if self.port_dropped.load(Ordering::SeqCst) { return UpDisconnected }
+
+        self.do_send(GoUp(up))
+    }
+
+    fn do_send(&self, t: Message<T>) -> UpgradeResult {
+        self.queue.push(t);
+        match self.cnt.fetch_add(1, Ordering::SeqCst) {
+            // As described in the mod's doc comment, -1 == wakeup
+            -1 => UpWoke(self.take_to_wake()),
+            // As as described before, SPSC queues must be >= -2
+            -2 => UpSuccess,
+
+            // Be sure to preserve the disconnected state, and the return value
+            // in this case is going to be whether our data was received or not.
+            // This manifests itself on whether we have an empty queue or not.
+            //
+            // Primarily, are required to drain the queue here because the port
+            // will never remove this data. We can only have at most one item to
+            // drain (the port drains the rest).
+            DISCONNECTED => {
+                self.cnt.store(DISCONNECTED, Ordering::SeqCst);
+                let first = self.queue.pop();
+                let second = self.queue.pop();
+                assert!(second.is_none());
+
+                match first {
+                    Some(..) => UpSuccess,  // we failed to send the data
+                    None => UpDisconnected, // we successfully sent data
+                }
+            }
+
+            // Otherwise we just sent some data on a non-waiting queue, so just
+            // make sure the world is sane and carry on!
+            n => { assert!(n >= 0); UpSuccess }
+        }
+    }
+
+    // Consumes ownership of the 'to_wake' field.
+    fn take_to_wake(&self) -> SignalToken {
+        let ptr = self.to_wake.load(Ordering::SeqCst);
+        self.to_wake.store(0, Ordering::SeqCst);
+        assert!(ptr != 0);
+        unsafe { SignalToken::cast_from_usize(ptr) }
+    }
+
+    // Decrements the count on the channel for a sleeper, returning the sleeper
+    // back if it shouldn't sleep. Note that this is the location where we take
+    // steals into account.
+    fn decrement(&self, token: SignalToken) -> Result<(), SignalToken> {
+        assert_eq!(self.to_wake.load(Ordering::SeqCst), 0);
+        let ptr = unsafe { token.cast_to_usize() };
+        self.to_wake.store(ptr, Ordering::SeqCst);
+
+        let steals = unsafe { ptr::replace(self.steals.get(), 0) };
+
+        match self.cnt.fetch_sub(1 + steals, Ordering::SeqCst) {
+            DISCONNECTED => { self.cnt.store(DISCONNECTED, Ordering::SeqCst); }
+            // If we factor in our steals and notice that the channel has no
+            // data, we successfully sleep
+            n => {
+                assert!(n >= 0);
+                if n - steals <= 0 { return Ok(()) }
+            }
+        }
+
+        self.to_wake.store(0, Ordering::SeqCst);
+        Err(unsafe { SignalToken::cast_from_usize(ptr) })
+    }
+
+    pub fn recv(&self, deadline: Option<Instant>) -> Result<T, Failure<T>> {
+        // Optimistic preflight check (scheduling is expensive).
+        match self.try_recv() {
+            Err(Empty) => {}
+            data => return data,
+        }
+
+        // Welp, our channel has no data. Deschedule the current thread and
+        // initiate the blocking protocol.
+        let (wait_token, signal_token) = blocking::tokens();
+        if self.decrement(signal_token).is_ok() {
+            if let Some(deadline) = deadline {
+                let timed_out = !wait_token.wait_max_until(deadline);
+                if timed_out {
+                    self.abort_selection(/* was_upgrade = */ false).map_err(Upgraded)?;
+                }
+            } else {
+                wait_token.wait();
+            }
+        }
+
+        match self.try_recv() {
+            // Messages which actually popped from the queue shouldn't count as
+            // a steal, so offset the decrement here (we already have our
+            // "steal" factored into the channel count above).
+            data @ Ok(..) |
+            data @ Err(Upgraded(..)) => unsafe {
+                *self.steals.get() -= 1;
+                data
+            },
+
+            data => data,
+        }
+    }
+
+    pub fn try_recv(&self) -> Result<T, Failure<T>> {
+        match self.queue.pop() {
+            // If we stole some data, record to that effect (this will be
+            // factored into cnt later on).
+            //
+            // Note that we don't allow steals to grow without bound in order to
+            // prevent eventual overflow of either steals or cnt as an overflow
+            // would have catastrophic results. Sometimes, steals > cnt, but
+            // other times cnt > steals, so we don't know the relation between
+            // steals and cnt. This code path is executed only rarely, so we do
+            // a pretty slow operation, of swapping 0 into cnt, taking steals
+            // down as much as possible (without going negative), and then
+            // adding back in whatever we couldn't factor into steals.
+            Some(data) => unsafe {
+                if *self.steals.get() > MAX_STEALS {
+                    match self.cnt.swap(0, Ordering::SeqCst) {
+                        DISCONNECTED => {
+                            self.cnt.store(DISCONNECTED, Ordering::SeqCst);
+                        }
+                        n => {
+                            let m = cmp::min(n, *self.steals.get());
+                            *self.steals.get() -= m;
+                            self.bump(n - m);
+                        }
+                    }
+                    assert!(*self.steals.get() >= 0);
+                }
+                *self.steals.get() += 1;
+                match data {
+                    Data(t) => Ok(t),
+                    GoUp(up) => Err(Upgraded(up)),
+                }
+            },
+
+            None => {
+                match self.cnt.load(Ordering::SeqCst) {
+                    n if n != DISCONNECTED => Err(Empty),
+
+                    // This is a little bit of a tricky case. We failed to pop
+                    // data above, and then we have viewed that the channel is
+                    // disconnected. In this window more data could have been
+                    // sent on the channel. It doesn't really make sense to
+                    // return that the channel is disconnected when there's
+                    // actually data on it, so be extra sure there's no data by
+                    // popping one more time.
+                    //
+                    // We can ignore steals because the other end is
+                    // disconnected and we'll never need to really factor in our
+                    // steals again.
+                    _ => {
+                        match self.queue.pop() {
+                            Some(Data(t)) => Ok(t),
+                            Some(GoUp(up)) => Err(Upgraded(up)),
+                            None => Err(Disconnected),
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    pub fn drop_chan(&self) {
+        // Dropping a channel is pretty simple, we just flag it as disconnected
+        // and then wakeup a blocker if there is one.
+        match self.cnt.swap(DISCONNECTED, Ordering::SeqCst) {
+            -1 => { self.take_to_wake().signal(); }
+            DISCONNECTED => {}
+            n => { assert!(n >= 0); }
+        }
+    }
+
+    pub fn drop_port(&self) {
+        // Dropping a port seems like a fairly trivial thing. In theory all we
+        // need to do is flag that we're disconnected and then everything else
+        // can take over (we don't have anyone to wake up).
+        //
+        // The catch for Ports is that we want to drop the entire contents of
+        // the queue. There are multiple reasons for having this property, the
+        // largest of which is that if another chan is waiting in this channel
+        // (but not received yet), then waiting on that port will cause a
+        // deadlock.
+        //
+        // So if we accept that we must now destroy the entire contents of the
+        // queue, this code may make a bit more sense. The tricky part is that
+        // we can't let any in-flight sends go un-dropped, we have to make sure
+        // *everything* is dropped and nothing new will come onto the channel.
+
+        // The first thing we do is set a flag saying that we're done for. All
+        // sends are gated on this flag, so we're immediately guaranteed that
+        // there are a bounded number of active sends that we'll have to deal
+        // with.
+        self.port_dropped.store(true, Ordering::SeqCst);
+
+        // Now that we're guaranteed to deal with a bounded number of senders,
+        // we need to drain the queue. This draining process happens atomically
+        // with respect to the "count" of the channel. If the count is nonzero
+        // (with steals taken into account), then there must be data on the
+        // channel. In this case we drain everything and then try again. We will
+        // continue to fail while active senders send data while we're dropping
+        // data, but eventually we're guaranteed to break out of this loop
+        // (because there is a bounded number of senders).
+        let mut steals = unsafe { *self.steals.get() };
+        while {
+            let cnt = self.cnt.compare_and_swap(
+                            steals, DISCONNECTED, Ordering::SeqCst);
+            cnt != DISCONNECTED && cnt != steals
+        } {
+            while let Some(_) = self.queue.pop() { steals += 1; }
+        }
+
+        // At this point in time, we have gated all future senders from sending,
+        // and we have flagged the channel as being disconnected. The senders
+        // still have some responsibility, however, because some sends may not
+        // complete until after we flag the disconnection. There are more
+        // details in the sending methods that see DISCONNECTED
+    }
+
+    ////////////////////////////////////////////////////////////////////////////
+    // select implementation
+    ////////////////////////////////////////////////////////////////////////////
+
+    // Tests to see whether this port can receive without blocking. If Ok is
+    // returned, then that's the answer. If Err is returned, then the returned
+    // port needs to be queried instead (an upgrade happened)
+    pub fn can_recv(&self) -> Result<bool, Receiver<T>> {
+        // We peek at the queue to see if there's anything on it, and we use
+        // this return value to determine if we should pop from the queue and
+        // upgrade this channel immediately. If it looks like we've got an
+        // upgrade pending, then go through the whole recv rigamarole to update
+        // the internal state.
+        match self.queue.peek() {
+            Some(&mut GoUp(..)) => {
+                match self.recv(None) {
+                    Err(Upgraded(port)) => Err(port),
+                    _ => unreachable!(),
+                }
+            }
+            Some(..) => Ok(true),
+            None => Ok(false)
+        }
+    }
+
+    // increment the count on the channel (used for selection)
+    fn bump(&self, amt: isize) -> isize {
+        match self.cnt.fetch_add(amt, Ordering::SeqCst) {
+            DISCONNECTED => {
+                self.cnt.store(DISCONNECTED, Ordering::SeqCst);
+                DISCONNECTED
+            }
+            n => n
+        }
+    }
+
+    // Attempts to start selecting on this port. Like a oneshot, this can fail
+    // immediately because of an upgrade.
+    pub fn start_selection(&self, token: SignalToken) -> SelectionResult<T> {
+        match self.decrement(token) {
+            Ok(()) => SelSuccess,
+            Err(token) => {
+                let ret = match self.queue.peek() {
+                    Some(&mut GoUp(..)) => {
+                        match self.queue.pop() {
+                            Some(GoUp(port)) => SelUpgraded(token, port),
+                            _ => unreachable!(),
+                        }
+                    }
+                    Some(..) => SelCanceled,
+                    None => SelCanceled,
+                };
+                // Undo our decrement above, and we should be guaranteed that the
+                // previous value is positive because we're not going to sleep
+                let prev = self.bump(1);
+                assert!(prev == DISCONNECTED || prev >= 0);
+                ret
+            }
+        }
+    }
+
+    // Removes a previous thread from being blocked in this port
+    pub fn abort_selection(&self,
+                           was_upgrade: bool) -> Result<bool, Receiver<T>> {
+        // If we're aborting selection after upgrading from a oneshot, then
+        // we're guarantee that no one is waiting. The only way that we could
+        // have seen the upgrade is if data was actually sent on the channel
+        // half again. For us, this means that there is guaranteed to be data on
+        // this channel. Furthermore, we're guaranteed that there was no
+        // start_selection previously, so there's no need to modify `self.cnt`
+        // at all.
+        //
+        // Hence, because of these invariants, we immediately return `Ok(true)`.
+        // Note that the data may not actually be sent on the channel just yet.
+        // The other end could have flagged the upgrade but not sent data to
+        // this end. This is fine because we know it's a small bounded windows
+        // of time until the data is actually sent.
+        if was_upgrade {
+            assert_eq!(unsafe { *self.steals.get() }, 0);
+            assert_eq!(self.to_wake.load(Ordering::SeqCst), 0);
+            return Ok(true)
+        }
+
+        // We want to make sure that the count on the channel goes non-negative,
+        // and in the stream case we can have at most one steal, so just assume
+        // that we had one steal.
+        let steals = 1;
+        let prev = self.bump(steals + 1);
+
+        // If we were previously disconnected, then we know for sure that there
+        // is no thread in to_wake, so just keep going
+        let has_data = if prev == DISCONNECTED {
+            assert_eq!(self.to_wake.load(Ordering::SeqCst), 0);
+            true // there is data, that data is that we're disconnected
+        } else {
+            let cur = prev + steals + 1;
+            assert!(cur >= 0);
+
+            // If the previous count was negative, then we just made things go
+            // positive, hence we passed the -1 boundary and we're responsible
+            // for removing the to_wake() field and trashing it.
+            //
+            // If the previous count was positive then we're in a tougher
+            // situation. A possible race is that a sender just incremented
+            // through -1 (meaning it's going to try to wake a thread up), but it
+            // hasn't yet read the to_wake. In order to prevent a future recv()
+            // from waking up too early (this sender picking up the plastered
+            // over to_wake), we spin loop here waiting for to_wake to be 0.
+            // Note that this entire select() implementation needs an overhaul,
+            // and this is *not* the worst part of it, so this is not done as a
+            // final solution but rather out of necessity for now to get
+            // something working.
+            if prev < 0 {
+                drop(self.take_to_wake());
+            } else {
+                while self.to_wake.load(Ordering::SeqCst) != 0 {
+                    thread::yield_now();
+                }
+            }
+            unsafe {
+                assert_eq!(*self.steals.get(), 0);
+                *self.steals.get() = steals;
+            }
+
+            // if we were previously positive, then there's surely data to
+            // receive
+            prev >= 0
+        };
+
+        // Now that we've determined that this queue "has data", we peek at the
+        // queue to see if the data is an upgrade or not. If it's an upgrade,
+        // then we need to destroy this port and abort selection on the
+        // upgraded port.
+        if has_data {
+            match self.queue.peek() {
+                Some(&mut GoUp(..)) => {
+                    match self.queue.pop() {
+                        Some(GoUp(port)) => Err(port),
+                        _ => unreachable!(),
+                    }
+                }
+                _ => Ok(true),
+            }
+        } else {
+            Ok(false)
+        }
+    }
+}
+
+impl<T> Drop for Packet<T> {
+    fn drop(&mut self) {
+        // Note that this load is not only an assert for correctness about
+        // disconnection, but also a proper fence before the read of
+        // `to_wake`, so this assert cannot be removed with also removing
+        // the `to_wake` assert.
+        assert_eq!(self.cnt.load(Ordering::SeqCst), DISCONNECTED);
+        assert_eq!(self.to_wake.load(Ordering::SeqCst), 0);
+    }
+}

ctr-std/src/sync/mpsc/sync.rs

@@ -0,0 +1,528 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/// Synchronous channels/ports
+///
+/// This channel implementation differs significantly from the asynchronous
+/// implementations found next to it (oneshot/stream/share). This is an
+/// implementation of a synchronous, bounded buffer channel.
+///
+/// Each channel is created with some amount of backing buffer, and sends will
+/// *block* until buffer space becomes available. A buffer size of 0 is valid,
+/// which means that every successful send is paired with a successful recv.
+///
+/// This flavor of channels defines a new `send_opt` method for channels which
+/// is the method by which a message is sent but the thread does not panic if it
+/// cannot be delivered.
+///
+/// Another major difference is that send() will *always* return back the data
+/// if it couldn't be sent. This is because it is deterministically known when
+/// the data is received and when it is not received.
+///
+/// Implementation-wise, it can all be summed up with "use a mutex plus some
+/// logic". The mutex used here is an OS native mutex, meaning that no user code
+/// is run inside of the mutex (to prevent context switching). This
+/// implementation shares almost all code for the buffered and unbuffered cases
+/// of a synchronous channel. There are a few branches for the unbuffered case,
+/// but they're mostly just relevant to blocking senders.
+
+pub use self::Failure::*;
+use self::Blocker::*;
+
+use core::intrinsics::abort;
+use core::isize;
+use core::mem;
+use core::ptr;
+
+use sync::atomic::{Ordering, AtomicUsize};
+use sync::mpsc::blocking::{self, WaitToken, SignalToken};
+use sync::mpsc::select::StartResult::{self, Installed, Abort};
+use sync::{Mutex, MutexGuard};
+use time::Instant;
+
+const MAX_REFCOUNT: usize = (isize::MAX) as usize;
+
+pub struct Packet<T> {
+    /// Only field outside of the mutex. Just done for kicks, but mainly because
+    /// the other shared channel already had the code implemented
+    channels: AtomicUsize,
+
+    lock: Mutex<State<T>>,
+}
+
+unsafe impl<T: Send> Send for Packet<T> { }
+
+unsafe impl<T: Send> Sync for Packet<T> { }
+
+struct State<T> {
+    disconnected: bool, // Is the channel disconnected yet?
+    queue: Queue,       // queue of senders waiting to send data
+    blocker: Blocker,   // currently blocked thread on this channel
+    buf: Buffer<T>,     // storage for buffered messages
+    cap: usize,         // capacity of this channel
+
+    /// A curious flag used to indicate whether a sender failed or succeeded in
+    /// blocking. This is used to transmit information back to the thread that it
+    /// must dequeue its message from the buffer because it was not received.
+    /// This is only relevant in the 0-buffer case. This obviously cannot be
+    /// safely constructed, but it's guaranteed to always have a valid pointer
+    /// value.
+    canceled: Option<&'static mut bool>,
+}
+
+unsafe impl<T: Send> Send for State<T> {}
+
+/// Possible flavors of threads who can be blocked on this channel.
+enum Blocker {
+    BlockedSender(SignalToken),
+    BlockedReceiver(SignalToken),
+    NoneBlocked
+}
+
+/// Simple queue for threading threads together. Nodes are stack-allocated, so
+/// this structure is not safe at all
+struct Queue {
+    head: *mut Node,
+    tail: *mut Node,
+}
+
+struct Node {
+    token: Option<SignalToken>,
+    next: *mut Node,
+}
+
+unsafe impl Send for Node {}
+
+/// A simple ring-buffer
+struct Buffer<T> {
+    buf: Vec<Option<T>>,
+    start: usize,
+    size: usize,
+}
+
+#[derive(Debug)]
+pub enum Failure {
+    Empty,
+    Disconnected,
+}
+
+/// Atomically blocks the current thread, placing it into `slot`, unlocking `lock`
+/// in the meantime. This re-locks the mutex upon returning.
+fn wait<'a, 'b, T>(lock: &'a Mutex<State<T>>,
+                   mut guard: MutexGuard<'b, State<T>>,
+                   f: fn(SignalToken) -> Blocker)
+                   -> MutexGuard<'a, State<T>>
+{
+    let (wait_token, signal_token) = blocking::tokens();
+    match mem::replace(&mut guard.blocker, f(signal_token)) {
+        NoneBlocked => {}
+        _ => unreachable!(),
+    }
+    drop(guard);         // unlock
+    wait_token.wait();   // block
+    lock.lock().unwrap() // relock
+}
+
+/// Same as wait, but waiting at most until `deadline`.
+fn wait_timeout_receiver<'a, 'b, T>(lock: &'a Mutex<State<T>>,
+                                    deadline: Instant,
+                                    mut guard: MutexGuard<'b, State<T>>,
+                                    success: &mut bool)
+                                    -> MutexGuard<'a, State<T>>
+{
+    let (wait_token, signal_token) = blocking::tokens();
+    match mem::replace(&mut guard.blocker, BlockedReceiver(signal_token)) {
+        NoneBlocked => {}
+        _ => unreachable!(),
+    }
+    drop(guard);         // unlock
+    *success = wait_token.wait_max_until(deadline);   // block
+    let mut new_guard = lock.lock().unwrap(); // relock
+    if !*success {
+        abort_selection(&mut new_guard);
+    }
+    new_guard
+}
+
+fn abort_selection<'a, T>(guard: &mut MutexGuard<'a , State<T>>) -> bool {
+    match mem::replace(&mut guard.blocker, NoneBlocked) {
+        NoneBlocked => true,
+        BlockedSender(token) => {
+            guard.blocker = BlockedSender(token);
+            true
+        }
+        BlockedReceiver(token) => { drop(token); false }
+    }
+}
+
+/// Wakes up a thread, dropping the lock at the correct time
+fn wakeup<T>(token: SignalToken, guard: MutexGuard<State<T>>) {
+    // We need to be careful to wake up the waiting thread *outside* of the mutex
+    // in case it incurs a context switch.
+    drop(guard);
+    token.signal();
+}
+
+impl<T> Packet<T> {
+    pub fn new(cap: usize) -> Packet<T> {
+        Packet {
+            channels: AtomicUsize::new(1),
+            lock: Mutex::new(State {
+                disconnected: false,
+                blocker: NoneBlocked,
+                cap: cap,
+                canceled: None,
+                queue: Queue {
+                    head: ptr::null_mut(),
+                    tail: ptr::null_mut(),
+                },
+                buf: Buffer {
+                    buf: (0..cap + if cap == 0 {1} else {0}).map(|_| None).collect(),
+                    start: 0,
+                    size: 0,
+                },
+            }),
+        }
+    }
+
+    // wait until a send slot is available, returning locked access to
+    // the channel state.
+    fn acquire_send_slot(&self) -> MutexGuard<State<T>> {
+        let mut node = Node { token: None, next: ptr::null_mut() };
+        loop {
+            let mut guard = self.lock.lock().unwrap();
+            // are we ready to go?
+            if guard.disconnected || guard.buf.size() < guard.buf.cap() {
+                return guard;
+            }
+            // no room; actually block
+            let wait_token = guard.queue.enqueue(&mut node);
+            drop(guard);
+            wait_token.wait();
+        }
+    }
+
+    pub fn send(&self, t: T) -> Result<(), T> {
+        let mut guard = self.acquire_send_slot();
+        if guard.disconnected { return Err(t) }
+        guard.buf.enqueue(t);
+
+        match mem::replace(&mut guard.blocker, NoneBlocked) {
+            // if our capacity is 0, then we need to wait for a receiver to be
+            // available to take our data. After waiting, we check again to make
+            // sure the port didn't go away in the meantime. If it did, we need
+            // to hand back our data.
+            NoneBlocked if guard.cap == 0 => {
+                let mut canceled = false;
+                assert!(guard.canceled.is_none());
+                guard.canceled = Some(unsafe { mem::transmute(&mut canceled) });
+                let mut guard = wait(&self.lock, guard, BlockedSender);
+                if canceled {Err(guard.buf.dequeue())} else {Ok(())}
+            }
+
+            // success, we buffered some data
+            NoneBlocked => Ok(()),
+
+            // success, someone's about to receive our buffered data.
+            BlockedReceiver(token) => { wakeup(token, guard); Ok(()) }
+
+            BlockedSender(..) => panic!("lolwut"),
+        }
+    }
+
+    pub fn try_send(&self, t: T) -> Result<(), super::TrySendError<T>> {
+        let mut guard = self.lock.lock().unwrap();
+        if guard.disconnected {
+            Err(super::TrySendError::Disconnected(t))
+        } else if guard.buf.size() == guard.buf.cap() {
+            Err(super::TrySendError::Full(t))
+        } else if guard.cap == 0 {
+            // With capacity 0, even though we have buffer space we can't
+            // transfer the data unless there's a receiver waiting.
+            match mem::replace(&mut guard.blocker, NoneBlocked) {
+                NoneBlocked => Err(super::TrySendError::Full(t)),
+                BlockedSender(..) => unreachable!(),
+                BlockedReceiver(token) => {
+                    guard.buf.enqueue(t);
+                    wakeup(token, guard);
+                    Ok(())
+                }
+            }
+        } else {
+            // If the buffer has some space and the capacity isn't 0, then we
+            // just enqueue the data for later retrieval, ensuring to wake up
+            // any blocked receiver if there is one.
+            assert!(guard.buf.size() < guard.buf.cap());
+            guard.buf.enqueue(t);
+            match mem::replace(&mut guard.blocker, NoneBlocked) {
+                BlockedReceiver(token) => wakeup(token, guard),
+                NoneBlocked => {}
+                BlockedSender(..) => unreachable!(),
+            }
+            Ok(())
+        }
+    }
+
+    // Receives a message from this channel
+    //
+    // When reading this, remember that there can only ever be one receiver at
+    // time.
+    pub fn recv(&self, deadline: Option<Instant>) -> Result<T, Failure> {
+        let mut guard = self.lock.lock().unwrap();
+
+        let mut woke_up_after_waiting = false;
+        // Wait for the buffer to have something in it. No need for a
+        // while loop because we're the only receiver.
+        if !guard.disconnected && guard.buf.size() == 0 {
+            if let Some(deadline) = deadline {
+                guard = wait_timeout_receiver(&self.lock,
+                                              deadline,
+                                              guard,
+                                              &mut woke_up_after_waiting);
+            } else {
+                guard = wait(&self.lock, guard, BlockedReceiver);
+                woke_up_after_waiting = true;
+            }
+        }
+
+        // NB: Channel could be disconnected while waiting, so the order of
+        // these conditionals is important.
+        if guard.disconnected && guard.buf.size() == 0 {
+            return Err(Disconnected);
+        }
+
+        // Pick up the data, wake up our neighbors, and carry on
+        assert!(guard.buf.size() > 0 || (deadline.is_some() && !woke_up_after_waiting));
+
+        if guard.buf.size() == 0 { return Err(Empty); }
+
+        let ret = guard.buf.dequeue();
+        self.wakeup_senders(woke_up_after_waiting, guard);
+        Ok(ret)
+    }
+
+    pub fn try_recv(&self) -> Result<T, Failure> {
+        let mut guard = self.lock.lock().unwrap();
+
+        // Easy cases first
+        if guard.disconnected && guard.buf.size() == 0 { return Err(Disconnected) }
+        if guard.buf.size() == 0 { return Err(Empty) }
+
+        // Be sure to wake up neighbors
+        let ret = Ok(guard.buf.dequeue());
+        self.wakeup_senders(false, guard);
+        ret
+    }
+
+    // Wake up pending senders after some data has been received
+    //
+    // * `waited` - flag if the receiver blocked to receive some data, or if it
+    //              just picked up some data on the way out
+    // * `guard` - the lock guard that is held over this channel's lock
+    fn wakeup_senders(&self, waited: bool, mut guard: MutexGuard<State<T>>) {
+        let pending_sender1: Option<SignalToken> = guard.queue.dequeue();
+
+        // If this is a no-buffer channel (cap == 0), then if we didn't wait we
+        // need to ACK the sender. If we waited, then the sender waking us up
+        // was already the ACK.
+        let pending_sender2 = if guard.cap == 0 && !waited {
+            match mem::replace(&mut guard.blocker, NoneBlocked) {
+                NoneBlocked => None,
+                BlockedReceiver(..) => unreachable!(),
+                BlockedSender(token) => {
+                    guard.canceled.take();
+                    Some(token)
+                }
+            }
+        } else {
+            None
+        };
+        mem::drop(guard);
+
+        // only outside of the lock do we wake up the pending threads
+        pending_sender1.map(|t| t.signal());
+        pending_sender2.map(|t| t.signal());
+    }
+
+    // Prepares this shared packet for a channel clone, essentially just bumping
+    // a refcount.
+    pub fn clone_chan(&self) {
+        let old_count = self.channels.fetch_add(1, Ordering::SeqCst);
+
+        // See comments on Arc::clone() on why we do this (for `mem::forget`).
+        if old_count > MAX_REFCOUNT {
+            unsafe {
+                abort();
+            }
+        }
+    }
+
+    pub fn drop_chan(&self) {
+        // Only flag the channel as disconnected if we're the last channel
+        match self.channels.fetch_sub(1, Ordering::SeqCst) {
+            1 => {}
+            _ => return
+        }
+
+        // Not much to do other than wake up a receiver if one's there
+        let mut guard = self.lock.lock().unwrap();
+        if guard.disconnected { return }
+        guard.disconnected = true;
+        match mem::replace(&mut guard.blocker, NoneBlocked) {
+            NoneBlocked => {}
+            BlockedSender(..) => unreachable!(),
+            BlockedReceiver(token) => wakeup(token, guard),
+        }
+    }
+
+    pub fn drop_port(&self) {
+        let mut guard = self.lock.lock().unwrap();
+
+        if guard.disconnected { return }
+        guard.disconnected = true;
+
+        // If the capacity is 0, then the sender may want its data back after
+        // we're disconnected. Otherwise it's now our responsibility to destroy
+        // the buffered data. As with many other portions of this code, this
+        // needs to be careful to destroy the data *outside* of the lock to
+        // prevent deadlock.
+        let _data = if guard.cap != 0 {
+            mem::replace(&mut guard.buf.buf, Vec::new())
+        } else {
+            Vec::new()
+        };
+        let mut queue = mem::replace(&mut guard.queue, Queue {
+            head: ptr::null_mut(),
+            tail: ptr::null_mut(),
+        });
+
+        let waiter = match mem::replace(&mut guard.blocker, NoneBlocked) {
+            NoneBlocked => None,
+            BlockedSender(token) => {
+                *guard.canceled.take().unwrap() = true;
+                Some(token)
+            }
+            BlockedReceiver(..) => unreachable!(),
+        };
+        mem::drop(guard);
+
+        while let Some(token) = queue.dequeue() { token.signal(); }
+        waiter.map(|t| t.signal());
+    }
+
+    ////////////////////////////////////////////////////////////////////////////
+    // select implementation
+    ////////////////////////////////////////////////////////////////////////////
+
+    // If Ok, the value is whether this port has data, if Err, then the upgraded
+    // port needs to be checked instead of this one.
+    pub fn can_recv(&self) -> bool {
+        let guard = self.lock.lock().unwrap();
+        guard.disconnected || guard.buf.size() > 0
+    }
+
+    // Attempts to start selection on this port. This can either succeed or fail
+    // because there is data waiting.
+    pub fn start_selection(&self, token: SignalToken) -> StartResult {
+        let mut guard = self.lock.lock().unwrap();
+        if guard.disconnected || guard.buf.size() > 0 {
+            Abort
+        } else {
+            match mem::replace(&mut guard.blocker, BlockedReceiver(token)) {
+                NoneBlocked => {}
+                BlockedSender(..) => unreachable!(),
+                BlockedReceiver(..) => unreachable!(),
+            }
+            Installed
+        }
+    }
+
+    // Remove a previous selecting thread from this port. This ensures that the
+    // blocked thread will no longer be visible to any other threads.
+    //
+    // The return value indicates whether there's data on this port.
+    pub fn abort_selection(&self) -> bool {
+        let mut guard = self.lock.lock().unwrap();
+        abort_selection(&mut guard)
+    }
+}
+
+impl<T> Drop for Packet<T> {
+    fn drop(&mut self) {
+        assert_eq!(self.channels.load(Ordering::SeqCst), 0);
+        let mut guard = self.lock.lock().unwrap();
+        assert!(guard.queue.dequeue().is_none());
+        assert!(guard.canceled.is_none());
+    }
+}
+
+
+////////////////////////////////////////////////////////////////////////////////
+// Buffer, a simple ring buffer backed by Vec<T>
+////////////////////////////////////////////////////////////////////////////////
+
+impl<T> Buffer<T> {
+    fn enqueue(&mut self, t: T) {
+        let pos = (self.start + self.size) % self.buf.len();
+        self.size += 1;
+        let prev = mem::replace(&mut self.buf[pos], Some(t));
+        assert!(prev.is_none());
+    }
+
+    fn dequeue(&mut self) -> T {
+        let start = self.start;
+        self.size -= 1;
+        self.start = (self.start + 1) % self.buf.len();
+        let result = &mut self.buf[start];
+        result.take().unwrap()
+    }
+
+    fn size(&self) -> usize { self.size }
+    fn cap(&self) -> usize { self.buf.len() }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Queue, a simple queue to enqueue threads with (stack-allocated nodes)
+////////////////////////////////////////////////////////////////////////////////
+
+impl Queue {
+    fn enqueue(&mut self, node: &mut Node) -> WaitToken {
+        let (wait_token, signal_token) = blocking::tokens();
+        node.token = Some(signal_token);
+        node.next = ptr::null_mut();
+
+        if self.tail.is_null() {
+            self.head = node as *mut Node;
+            self.tail = node as *mut Node;
+        } else {
+            unsafe {
+                (*self.tail).next = node as *mut Node;
+                self.tail = node as *mut Node;
+            }
+        }
+
+        wait_token
+    }
+
+    fn dequeue(&mut self) -> Option<SignalToken> {
+        if self.head.is_null() {
+            return None
+        }
+        let node = self.head;
+        self.head = unsafe { (*node).next };
+        if self.head.is_null() {
+            self.tail = ptr::null_mut();
+        }
+        unsafe {
+            (*node).next = ptr::null_mut();
+            Some((*node).token.take().unwrap())
+        }
+    }
+}

ctr-std/src/sync/mutex.rs

@@ -133,11 +133,13 @@ unsafe impl<T: ?Sized + Send> Sync for Mutex<T> { }
 /// dropped (falls out of scope), the lock will be unlocked.
 ///
 /// The data protected by the mutex can be access through this guard via its
-/// `Deref` and `DerefMut` implementations.
+/// [`Deref`] and [`DerefMut`] implementations.
 ///
 /// This structure is created by the [`lock()`] and [`try_lock()`] methods on
 /// [`Mutex`].
 ///
+/// [`Deref`]: ../../std/ops/trait.Deref.html
+/// [`DerefMut`]: ../../std/ops/trait.DerefMut.html
 /// [`lock()`]: struct.Mutex.html#method.lock
 /// [`try_lock()`]: struct.Mutex.html#method.try_lock
 /// [`Mutex`]: struct.Mutex.html

ctr-std/src/sync/once.rs

@@ -0,0 +1,496 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! A "once initialization" primitive
+//!
+//! This primitive is meant to be used to run one-time initialization. An
+//! example use case would be for initializing an FFI library.
+
+// A "once" is a relatively simple primitive, and it's also typically provided
+// by the OS as well (see `pthread_once` or `InitOnceExecuteOnce`). The OS
+// primitives, however, tend to have surprising restrictions, such as the Unix
+// one doesn't allow an argument to be passed to the function.
+//
+// As a result, we end up implementing it ourselves in the standard library.
+// This also gives us the opportunity to optimize the implementation a bit which
+// should help the fast path on call sites. Consequently, let's explain how this
+// primitive works now!
+//
+// So to recap, the guarantees of a Once are that it will call the
+// initialization closure at most once, and it will never return until the one
+// that's running has finished running. This means that we need some form of
+// blocking here while the custom callback is running at the very least.
+// Additionally, we add on the restriction of **poisoning**. Whenever an
+// initialization closure panics, the Once enters a "poisoned" state which means
+// that all future calls will immediately panic as well.
+//
+// So to implement this, one might first reach for a `StaticMutex`, but those
+// unfortunately need to be deallocated (e.g. call `destroy()`) to free memory
+// on all OSes (some of the BSDs allocate memory for mutexes). It also gets a
+// lot harder with poisoning to figure out when the mutex needs to be
+// deallocated because it's not after the closure finishes, but after the first
+// successful closure finishes.
+//
+// All in all, this is instead implemented with atomics and lock-free
+// operations! Whee! Each `Once` has one word of atomic state, and this state is
+// CAS'd on to determine what to do. There are four possible state of a `Once`:
+//
+// * Incomplete - no initialization has run yet, and no thread is currently
+//                using the Once.
+// * Poisoned - some thread has previously attempted to initialize the Once, but
+//              it panicked, so the Once is now poisoned. There are no other
+//              threads currently accessing this Once.
+// * Running - some thread is currently attempting to run initialization. It may
+//             succeed, so all future threads need to wait for it to finish.
+//             Note that this state is accompanied with a payload, described
+//             below.
+// * Complete - initialization has completed and all future calls should finish
+//              immediately.
+//
+// With 4 states we need 2 bits to encode this, and we use the remaining bits
+// in the word we have allocated as a queue of threads waiting for the thread
+// responsible for entering the RUNNING state. This queue is just a linked list
+// of Waiter nodes which is monotonically increasing in size. Each node is
+// allocated on the stack, and whenever the running closure finishes it will
+// consume the entire queue and notify all waiters they should try again.
+//
+// You'll find a few more details in the implementation, but that's the gist of
+// it!
+
+use fmt;
+use marker;
+use ptr;
+use sync::atomic::{AtomicUsize, AtomicBool, Ordering};
+use thread::{self, Thread};
+
+/// A synchronization primitive which can be used to run a one-time global
+/// initialization. Useful for one-time initialization for FFI or related
+/// functionality. This type can only be constructed with the `ONCE_INIT`
+/// value.
+///
+/// # Examples
+///
+/// ```
+/// use std::sync::{Once, ONCE_INIT};
+///
+/// static START: Once = ONCE_INIT;
+///
+/// START.call_once(|| {
+///     // run initialization here
+/// });
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct Once {
+    // This `state` word is actually an encoded version of just a pointer to a
+    // `Waiter`, so we add the `PhantomData` appropriately.
+    state: AtomicUsize,
+    _marker: marker::PhantomData<*mut Waiter>,
+}
+
+// The `PhantomData` of a raw pointer removes these two auto traits, but we
+// enforce both below in the implementation so this should be safe to add.
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl Sync for Once {}
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl Send for Once {}
+
+/// State yielded to the `call_once_force` method which can be used to query
+/// whether the `Once` was previously poisoned or not.
+#[unstable(feature = "once_poison", issue = "33577")]
+#[derive(Debug)]
+pub struct OnceState {
+    poisoned: bool,
+}
+
+/// Initialization value for static `Once` values.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub const ONCE_INIT: Once = Once::new();
+
+// Four states that a Once can be in, encoded into the lower bits of `state` in
+// the Once structure.
+const INCOMPLETE: usize = 0x0;
+const POISONED: usize = 0x1;
+const RUNNING: usize = 0x2;
+const COMPLETE: usize = 0x3;
+
+// Mask to learn about the state. All other bits are the queue of waiters if
+// this is in the RUNNING state.
+const STATE_MASK: usize = 0x3;
+
+// Representation of a node in the linked list of waiters in the RUNNING state.
+struct Waiter {
+    thread: Option<Thread>,
+    signaled: AtomicBool,
+    next: *mut Waiter,
+}
+
+// Helper struct used to clean up after a closure call with a `Drop`
+// implementation to also run on panic.
+struct Finish {
+    panicked: bool,
+    me: &'static Once,
+}
+
+impl Once {
+    /// Creates a new `Once` value.
+    #[stable(feature = "once_new", since = "1.2.0")]
+    pub const fn new() -> Once {
+        Once {
+            state: AtomicUsize::new(INCOMPLETE),
+            _marker: marker::PhantomData,
+        }
+    }
+
+    /// Performs an initialization routine once and only once. The given closure
+    /// will be executed if this is the first time `call_once` has been called,
+    /// and otherwise the routine will *not* be invoked.
+    ///
+    /// This method will block the calling thread if another initialization
+    /// routine is currently running.
+    ///
+    /// When this function returns, it is guaranteed that some initialization
+    /// has run and completed (it may not be the closure specified). It is also
+    /// guaranteed that any memory writes performed by the executed closure can
+    /// be reliably observed by other threads at this point (there is a
+    /// happens-before relation between the closure and code executing after the
+    /// return).
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::{Once, ONCE_INIT};
+    ///
+    /// static mut VAL: usize = 0;
+    /// static INIT: Once = ONCE_INIT;
+    ///
+    /// // Accessing a `static mut` is unsafe much of the time, but if we do so
+    /// // in a synchronized fashion (e.g. write once or read all) then we're
+    /// // good to go!
+    /// //
+    /// // This function will only call `expensive_computation` once, and will
+    /// // otherwise always return the value returned from the first invocation.
+    /// fn get_cached_val() -> usize {
+    ///     unsafe {
+    ///         INIT.call_once(|| {
+    ///             VAL = expensive_computation();
+    ///         });
+    ///         VAL
+    ///     }
+    /// }
+    ///
+    /// fn expensive_computation() -> usize {
+    ///     // ...
+    /// # 2
+    /// }
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// The closure `f` will only be executed once if this is called
+    /// concurrently amongst many threads. If that closure panics, however, then
+    /// it will *poison* this `Once` instance, causing all future invocations of
+    /// `call_once` to also panic.
+    ///
+    /// This is similar to [poisoning with mutexes][poison].
+    ///
+    /// [poison]: struct.Mutex.html#poisoning
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn call_once<F>(&'static self, f: F) where F: FnOnce() {
+        // Fast path, just see if we've completed initialization.
+        if self.state.load(Ordering::SeqCst) == COMPLETE {
+            return
+        }
+
+        let mut f = Some(f);
+        self.call_inner(false, &mut |_| f.take().unwrap()());
+    }
+
+    /// Performs the same function as `call_once` except ignores poisoning.
+    ///
+    /// If this `Once` has been poisoned (some initialization panicked) then
+    /// this function will continue to attempt to call initialization functions
+    /// until one of them doesn't panic.
+    ///
+    /// The closure `f` is yielded a structure which can be used to query the
+    /// state of this `Once` (whether initialization has previously panicked or
+    /// not).
+    #[unstable(feature = "once_poison", issue = "33577")]
+    pub fn call_once_force<F>(&'static self, f: F) where F: FnOnce(&OnceState) {
+        // same as above, just with a different parameter to `call_inner`.
+        if self.state.load(Ordering::SeqCst) == COMPLETE {
+            return
+        }
+
+        let mut f = Some(f);
+        self.call_inner(true, &mut |p| {
+            f.take().unwrap()(&OnceState { poisoned: p })
+        });
+    }
+
+    // This is a non-generic function to reduce the monomorphization cost of
+    // using `call_once` (this isn't exactly a trivial or small implementation).
+    //
+    // Additionally, this is tagged with `#[cold]` as it should indeed be cold
+    // and it helps let LLVM know that calls to this function should be off the
+    // fast path. Essentially, this should help generate more straight line code
+    // in LLVM.
+    //
+    // Finally, this takes an `FnMut` instead of a `FnOnce` because there's
+    // currently no way to take an `FnOnce` and call it via virtual dispatch
+    // without some allocation overhead.
+    #[cold]
+    fn call_inner(&'static self,
+                  ignore_poisoning: bool,
+                  mut init: &mut FnMut(bool)) {
+        let mut state = self.state.load(Ordering::SeqCst);
+
+        'outer: loop {
+            match state {
+                // If we're complete, then there's nothing to do, we just
+                // jettison out as we shouldn't run the closure.
+                COMPLETE => return,
+
+                // If we're poisoned and we're not in a mode to ignore
+                // poisoning, then we panic here to propagate the poison.
+                POISONED if !ignore_poisoning => {
+                    panic!("Once instance has previously been poisoned");
+                }
+
+                // Otherwise if we see a poisoned or otherwise incomplete state
+                // we will attempt to move ourselves into the RUNNING state. If
+                // we succeed, then the queue of waiters starts at null (all 0
+                // bits).
+                POISONED |
+                INCOMPLETE => {
+                    let old = self.state.compare_and_swap(state, RUNNING,
+                                                          Ordering::SeqCst);
+                    if old != state {
+                        state = old;
+                        continue
+                    }
+
+                    // Run the initialization routine, letting it know if we're
+                    // poisoned or not. The `Finish` struct is then dropped, and
+                    // the `Drop` implementation here is responsible for waking
+                    // up other waiters both in the normal return and panicking
+                    // case.
+                    let mut complete = Finish {
+                        panicked: true,
+                        me: self,
+                    };
+                    init(state == POISONED);
+                    complete.panicked = false;
+                    return
+                }
+
+                // All other values we find should correspond to the RUNNING
+                // state with an encoded waiter list in the more significant
+                // bits. We attempt to enqueue ourselves by moving us to the
+                // head of the list and bail out if we ever see a state that's
+                // not RUNNING.
+                _ => {
+                    assert!(state & STATE_MASK == RUNNING);
+                    let mut node = Waiter {
+                        thread: Some(thread::current()),
+                        signaled: AtomicBool::new(false),
+                        next: ptr::null_mut(),
+                    };
+                    let me = &mut node as *mut Waiter as usize;
+                    assert!(me & STATE_MASK == 0);
+
+                    while state & STATE_MASK == RUNNING {
+                        node.next = (state & !STATE_MASK) as *mut Waiter;
+                        let old = self.state.compare_and_swap(state,
+                                                              me | RUNNING,
+                                                              Ordering::SeqCst);
+                        if old != state {
+                            state = old;
+                            continue
+                        }
+
+                        // Once we've enqueued ourselves, wait in a loop.
+                        // Afterwards reload the state and continue with what we
+                        // were doing from before.
+                        while !node.signaled.load(Ordering::SeqCst) {
+                            thread::park();
+                        }
+                        state = self.state.load(Ordering::SeqCst);
+                        continue 'outer
+                    }
+                }
+            }
+        }
+    }
+}
+
+#[stable(feature = "std_debug", since = "1.16.0")]
+impl fmt::Debug for Once {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("Once { .. }")
+    }
+}
+
+impl Drop for Finish {
+    fn drop(&mut self) {
+        // Swap out our state with however we finished. We should only ever see
+        // an old state which was RUNNING.
+        let queue = if self.panicked {
+            self.me.state.swap(POISONED, Ordering::SeqCst)
+        } else {
+            self.me.state.swap(COMPLETE, Ordering::SeqCst)
+        };
+        assert_eq!(queue & STATE_MASK, RUNNING);
+
+        // Decode the RUNNING to a list of waiters, then walk that entire list
+        // and wake them up. Note that it is crucial that after we store `true`
+        // in the node it can be free'd! As a result we load the `thread` to
+        // signal ahead of time and then unpark it after the store.
+        unsafe {
+            let mut queue = (queue & !STATE_MASK) as *mut Waiter;
+            while !queue.is_null() {
+                let next = (*queue).next;
+                let thread = (*queue).thread.take().unwrap();
+                (*queue).signaled.store(true, Ordering::SeqCst);
+                thread.unpark();
+                queue = next;
+            }
+        }
+    }
+}
+
+impl OnceState {
+    /// Returns whether the associated `Once` has been poisoned.
+    ///
+    /// Once an initalization routine for a `Once` has panicked it will forever
+    /// indicate to future forced initialization routines that it is poisoned.
+    #[unstable(feature = "once_poison", issue = "33577")]
+    pub fn poisoned(&self) -> bool {
+        self.poisoned
+    }
+}
+
+#[cfg(all(test, not(target_os = "emscripten")))]
+mod tests {
+    use panic;
+    use sync::mpsc::channel;
+    use thread;
+    use super::Once;
+
+    #[test]
+    fn smoke_once() {
+        static O: Once = Once::new();
+        let mut a = 0;
+        O.call_once(|| a += 1);
+        assert_eq!(a, 1);
+        O.call_once(|| a += 1);
+        assert_eq!(a, 1);
+    }
+
+    #[test]
+    fn stampede_once() {
+        static O: Once = Once::new();
+        static mut RUN: bool = false;
+
+        let (tx, rx) = channel();
+        for _ in 0..10 {
+            let tx = tx.clone();
+            thread::spawn(move|| {
+                for _ in 0..4 { thread::yield_now() }
+                unsafe {
+                    O.call_once(|| {
+                        assert!(!RUN);
+                        RUN = true;
+                    });
+                    assert!(RUN);
+                }
+                tx.send(()).unwrap();
+            });
+        }
+
+        unsafe {
+            O.call_once(|| {
+                assert!(!RUN);
+                RUN = true;
+            });
+            assert!(RUN);
+        }
+
+        for _ in 0..10 {
+            rx.recv().unwrap();
+        }
+    }
+
+    #[test]
+    fn poison_bad() {
+        static O: Once = Once::new();
+
+        // poison the once
+        let t = panic::catch_unwind(|| {
+            O.call_once(|| panic!());
+        });
+        assert!(t.is_err());
+
+        // poisoning propagates
+        let t = panic::catch_unwind(|| {
+            O.call_once(|| {});
+        });
+        assert!(t.is_err());
+
+        // we can subvert poisoning, however
+        let mut called = false;
+        O.call_once_force(|p| {
+            called = true;
+            assert!(p.poisoned())
+        });
+        assert!(called);
+
+        // once any success happens, we stop propagating the poison
+        O.call_once(|| {});
+    }
+
+    #[test]
+    fn wait_for_force_to_finish() {
+        static O: Once = Once::new();
+
+        // poison the once
+        let t = panic::catch_unwind(|| {
+            O.call_once(|| panic!());
+        });
+        assert!(t.is_err());
+
+        // make sure someone's waiting inside the once via a force
+        let (tx1, rx1) = channel();
+        let (tx2, rx2) = channel();
+        let t1 = thread::spawn(move || {
+            O.call_once_force(|p| {
+                assert!(p.poisoned());
+                tx1.send(()).unwrap();
+                rx2.recv().unwrap();
+            });
+        });
+
+        rx1.recv().unwrap();
+
+        // put another waiter on the once
+        let t2 = thread::spawn(|| {
+            let mut called = false;
+            O.call_once(|| {
+                called = true;
+            });
+            assert!(!called);
+        });
+
+        tx2.send(()).unwrap();
+
+        assert!(t1.join().is_ok());
+        assert!(t2.join().is_ok());
+
+    }
+}

ctr-std/src/sync/rwlock.rs

@@ -0,0 +1,666 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use cell::UnsafeCell;
+use fmt;
+use marker;
+use mem;
+use ops::{Deref, DerefMut};
+use ptr;
+use sys_common::poison::{self, LockResult, TryLockError, TryLockResult};
+use sys_common::rwlock as sys;
+
+/// A reader-writer lock
+///
+/// This type of lock allows a number of readers or at most one writer at any
+/// point in time. The write portion of this lock typically allows modification
+/// of the underlying data (exclusive access) and the read portion of this lock
+/// typically allows for read-only access (shared access).
+///
+/// The priority policy of the lock is dependent on the underlying operating
+/// system's implementation, and this type does not guarantee that any
+/// particular policy will be used.
+///
+/// The type parameter `T` represents the data that this lock protects. It is
+/// required that `T` satisfies `Send` to be shared across threads and `Sync` to
+/// allow concurrent access through readers. The RAII guards returned from the
+/// locking methods implement `Deref` (and `DerefMut` for the `write` methods)
+/// to allow access to the contained of the lock.
+///
+/// # Poisoning
+///
+/// An `RwLock`, like `Mutex`, will become poisoned on a panic. Note, however,
+/// that an `RwLock` may only be poisoned if a panic occurs while it is locked
+/// exclusively (write mode). If a panic occurs in any reader, then the lock
+/// will not be poisoned.
+///
+/// # Examples
+///
+/// ```
+/// use std::sync::RwLock;
+///
+/// let lock = RwLock::new(5);
+///
+/// // many reader locks can be held at once
+/// {
+///     let r1 = lock.read().unwrap();
+///     let r2 = lock.read().unwrap();
+///     assert_eq!(*r1, 5);
+///     assert_eq!(*r2, 5);
+/// } // read locks are dropped at this point
+///
+/// // only one write lock may be held, however
+/// {
+///     let mut w = lock.write().unwrap();
+///     *w += 1;
+///     assert_eq!(*w, 6);
+/// } // write lock is dropped here
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct RwLock<T: ?Sized> {
+    inner: Box<sys::RWLock>,
+    poison: poison::Flag,
+    data: UnsafeCell<T>,
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<T: ?Sized + Send + Sync> Send for RwLock<T> {}
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<T: ?Sized + Send + Sync> Sync for RwLock<T> {}
+
+/// RAII structure used to release the shared read access of a lock when
+/// dropped.
+///
+/// This structure is created by the [`read()`] and [`try_read()`] methods on
+/// [`RwLock`].
+///
+/// [`read()`]: struct.RwLock.html#method.read
+/// [`try_read()`]: struct.RwLock.html#method.try_read
+/// [`RwLock`]: struct.RwLock.html
+#[must_use]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct RwLockReadGuard<'a, T: ?Sized + 'a> {
+    __lock: &'a RwLock<T>,
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, T: ?Sized> !marker::Send for RwLockReadGuard<'a, T> {}
+
+/// RAII structure used to release the exclusive write access of a lock when
+/// dropped.
+///
+/// This structure is created by the [`write()`] and [`try_write()`] methods
+/// on [`RwLock`].
+///
+/// [`write()`]: struct.RwLock.html#method.write
+/// [`try_write()`]: struct.RwLock.html#method.try_write
+/// [`RwLock`]: struct.RwLock.html
+#[must_use]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct RwLockWriteGuard<'a, T: ?Sized + 'a> {
+    __lock: &'a RwLock<T>,
+    __poison: poison::Guard,
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, T: ?Sized> !marker::Send for RwLockWriteGuard<'a, T> {}
+
+impl<T> RwLock<T> {
+    /// Creates a new instance of an `RwLock<T>` which is unlocked.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::RwLock;
+    ///
+    /// let lock = RwLock::new(5);
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn new(t: T) -> RwLock<T> {
+        RwLock {
+            inner: box sys::RWLock::new(),
+            poison: poison::Flag::new(),
+            data: UnsafeCell::new(t),
+        }
+    }
+}
+
+impl<T: ?Sized> RwLock<T> {
+    /// Locks this rwlock with shared read access, blocking the current thread
+    /// until it can be acquired.
+    ///
+    /// The calling thread will be blocked until there are no more writers which
+    /// hold the lock. There may be other readers currently inside the lock when
+    /// this method returns. This method does not provide any guarantees with
+    /// respect to the ordering of whether contentious readers or writers will
+    /// acquire the lock first.
+    ///
+    /// Returns an RAII guard which will release this thread's shared access
+    /// once it is dropped.
+    ///
+    /// # Errors
+    ///
+    /// This function will return an error if the RwLock is poisoned. An RwLock
+    /// is poisoned whenever a writer panics while holding an exclusive lock.
+    /// The failure will occur immediately after the lock has been acquired.
+    ///
+    /// # Panics
+    ///
+    /// This function might panic when called if the lock is already held by the current thread.
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn read(&self) -> LockResult<RwLockReadGuard<T>> {
+        unsafe {
+            self.inner.read();
+            RwLockReadGuard::new(self)
+        }
+    }
+
+    /// Attempts to acquire this rwlock with shared read access.
+    ///
+    /// If the access could not be granted at this time, then `Err` is returned.
+    /// Otherwise, an RAII guard is returned which will release the shared access
+    /// when it is dropped.
+    ///
+    /// This function does not block.
+    ///
+    /// This function does not provide any guarantees with respect to the ordering
+    /// of whether contentious readers or writers will acquire the lock first.
+    ///
+    /// # Errors
+    ///
+    /// This function will return an error if the RwLock is poisoned. An RwLock
+    /// is poisoned whenever a writer panics while holding an exclusive lock. An
+    /// error will only be returned if the lock would have otherwise been
+    /// acquired.
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn try_read(&self) -> TryLockResult<RwLockReadGuard<T>> {
+        unsafe {
+            if self.inner.try_read() {
+                Ok(RwLockReadGuard::new(self)?)
+            } else {
+                Err(TryLockError::WouldBlock)
+            }
+        }
+    }
+
+    /// Locks this rwlock with exclusive write access, blocking the current
+    /// thread until it can be acquired.
+    ///
+    /// This function will not return while other writers or other readers
+    /// currently have access to the lock.
+    ///
+    /// Returns an RAII guard which will drop the write access of this rwlock
+    /// when dropped.
+    ///
+    /// # Errors
+    ///
+    /// This function will return an error if the RwLock is poisoned. An RwLock
+    /// is poisoned whenever a writer panics while holding an exclusive lock.
+    /// An error will be returned when the lock is acquired.
+    ///
+    /// # Panics
+    ///
+    /// This function might panic when called if the lock is already held by the current thread.
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn write(&self) -> LockResult<RwLockWriteGuard<T>> {
+        unsafe {
+            self.inner.write();
+            RwLockWriteGuard::new(self)
+        }
+    }
+
+    /// Attempts to lock this rwlock with exclusive write access.
+    ///
+    /// If the lock could not be acquired at this time, then `Err` is returned.
+    /// Otherwise, an RAII guard is returned which will release the lock when
+    /// it is dropped.
+    ///
+    /// This function does not block.
+    ///
+    /// This function does not provide any guarantees with respect to the ordering
+    /// of whether contentious readers or writers will acquire the lock first.
+    ///
+    /// # Errors
+    ///
+    /// This function will return an error if the RwLock is poisoned. An RwLock
+    /// is poisoned whenever a writer panics while holding an exclusive lock. An
+    /// error will only be returned if the lock would have otherwise been
+    /// acquired.
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn try_write(&self) -> TryLockResult<RwLockWriteGuard<T>> {
+        unsafe {
+            if self.inner.try_write() {
+                Ok(RwLockWriteGuard::new(self)?)
+            } else {
+                Err(TryLockError::WouldBlock)
+            }
+        }
+    }
+
+    /// Determines whether the lock is poisoned.
+    ///
+    /// If another thread is active, the lock can still become poisoned at any
+    /// time.  You should not trust a `false` value for program correctness
+    /// without additional synchronization.
+    #[inline]
+    #[stable(feature = "sync_poison", since = "1.2.0")]
+    pub fn is_poisoned(&self) -> bool {
+        self.poison.get()
+    }
+
+    /// Consumes this `RwLock`, returning the underlying data.
+    ///
+    /// # Errors
+    ///
+    /// This function will return an error if the RwLock is poisoned. An RwLock
+    /// is poisoned whenever a writer panics while holding an exclusive lock. An
+    /// error will only be returned if the lock would have otherwise been
+    /// acquired.
+    #[stable(feature = "rwlock_into_inner", since = "1.6.0")]
+    pub fn into_inner(self) -> LockResult<T> where T: Sized {
+        // We know statically that there are no outstanding references to
+        // `self` so there's no need to lock the inner lock.
+        //
+        // To get the inner value, we'd like to call `data.into_inner()`,
+        // but because `RwLock` impl-s `Drop`, we can't move out of it, so
+        // we'll have to destructure it manually instead.
+        unsafe {
+            // Like `let RwLock { inner, poison, data } = self`.
+            let (inner, poison, data) = {
+                let RwLock { ref inner, ref poison, ref data } = self;
+                (ptr::read(inner), ptr::read(poison), ptr::read(data))
+            };
+            mem::forget(self);
+            inner.destroy();  // Keep in sync with the `Drop` impl.
+            drop(inner);
+
+            poison::map_result(poison.borrow(), |_| data.into_inner())
+        }
+    }
+
+    /// Returns a mutable reference to the underlying data.
+    ///
+    /// Since this call borrows the `RwLock` mutably, no actual locking needs to
+    /// take place---the mutable borrow statically guarantees no locks exist.
+    ///
+    /// # Errors
+    ///
+    /// This function will return an error if the RwLock is poisoned. An RwLock
+    /// is poisoned whenever a writer panics while holding an exclusive lock. An
+    /// error will only be returned if the lock would have otherwise been
+    /// acquired.
+    #[stable(feature = "rwlock_get_mut", since = "1.6.0")]
+    pub fn get_mut(&mut self) -> LockResult<&mut T> {
+        // We know statically that there are no other references to `self`, so
+        // there's no need to lock the inner lock.
+        let data = unsafe { &mut *self.data.get() };
+        poison::map_result(self.poison.borrow(), |_| data)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<#[may_dangle] T: ?Sized> Drop for RwLock<T> {
+    fn drop(&mut self) {
+        // IMPORTANT: This code needs to be kept in sync with `RwLock::into_inner`.
+        unsafe { self.inner.destroy() }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + fmt::Debug> fmt::Debug for RwLock<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self.try_read() {
+            Ok(guard) => write!(f, "RwLock {{ data: {:?} }}", &*guard),
+            Err(TryLockError::Poisoned(err)) => {
+                write!(f, "RwLock {{ data: Poisoned({:?}) }}", &**err.get_ref())
+            },
+            Err(TryLockError::WouldBlock) => write!(f, "RwLock {{ <locked> }}")
+        }
+    }
+}
+
+#[stable(feature = "rw_lock_default", since = "1.9.0")]
+impl<T: Default> Default for RwLock<T> {
+    /// Creates a new `RwLock<T>`, with the `Default` value for T.
+    fn default() -> RwLock<T> {
+        RwLock::new(Default::default())
+    }
+}
+
+impl<'rwlock, T: ?Sized> RwLockReadGuard<'rwlock, T> {
+    unsafe fn new(lock: &'rwlock RwLock<T>)
+                  -> LockResult<RwLockReadGuard<'rwlock, T>> {
+        poison::map_result(lock.poison.borrow(), |_| {
+            RwLockReadGuard {
+                __lock: lock,
+            }
+        })
+    }
+}
+
+impl<'rwlock, T: ?Sized> RwLockWriteGuard<'rwlock, T> {
+    unsafe fn new(lock: &'rwlock RwLock<T>)
+                  -> LockResult<RwLockWriteGuard<'rwlock, T>> {
+        poison::map_result(lock.poison.borrow(), |guard| {
+            RwLockWriteGuard {
+                __lock: lock,
+                __poison: guard,
+            }
+        })
+    }
+}
+
+#[stable(feature = "std_debug", since = "1.16.0")]
+impl<'a, T: fmt::Debug> fmt::Debug for RwLockReadGuard<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("RwLockReadGuard")
+            .field("lock", &self.__lock)
+            .finish()
+    }
+}
+
+#[stable(feature = "std_debug", since = "1.16.0")]
+impl<'a, T: fmt::Debug> fmt::Debug for RwLockWriteGuard<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("RwLockWriteGuard")
+            .field("lock", &self.__lock)
+            .finish()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'rwlock, T: ?Sized> Deref for RwLockReadGuard<'rwlock, T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        unsafe { &*self.__lock.data.get() }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'rwlock, T: ?Sized> Deref for RwLockWriteGuard<'rwlock, T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        unsafe { &*self.__lock.data.get() }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'rwlock, T: ?Sized> DerefMut for RwLockWriteGuard<'rwlock, T> {
+    fn deref_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.__lock.data.get() }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, T: ?Sized> Drop for RwLockReadGuard<'a, T> {
+    fn drop(&mut self) {
+        unsafe { self.__lock.inner.read_unlock(); }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, T: ?Sized> Drop for RwLockWriteGuard<'a, T> {
+    fn drop(&mut self) {
+        self.__lock.poison.done(&self.__poison);
+        unsafe { self.__lock.inner.write_unlock(); }
+    }
+}
+
+#[cfg(all(test, not(target_os = "emscripten")))]
+mod tests {
+    #![allow(deprecated)] // rand
+
+    use rand::{self, Rng};
+    use sync::mpsc::channel;
+    use thread;
+    use sync::{Arc, RwLock, TryLockError};
+    use sync::atomic::{AtomicUsize, Ordering};
+
+    #[derive(Eq, PartialEq, Debug)]
+    struct NonCopy(i32);
+
+    #[test]
+    fn smoke() {
+        let l = RwLock::new(());
+        drop(l.read().unwrap());
+        drop(l.write().unwrap());
+        drop((l.read().unwrap(), l.read().unwrap()));
+        drop(l.write().unwrap());
+    }
+
+    #[test]
+    fn frob() {
+        const N: usize = 10;
+        const M: usize = 1000;
+
+        let r = Arc::new(RwLock::new(()));
+
+        let (tx, rx) = channel::<()>();
+        for _ in 0..N {
+            let tx = tx.clone();
+            let r = r.clone();
+            thread::spawn(move || {
+                let mut rng = rand::thread_rng();
+                for _ in 0..M {
+                    if rng.gen_weighted_bool(N) {
+                        drop(r.write().unwrap());
+                    } else {
+                        drop(r.read().unwrap());
+                    }
+                }
+                drop(tx);
+            });
+        }
+        drop(tx);
+        let _ = rx.recv();
+    }
+
+    #[test]
+    fn test_rw_arc_poison_wr() {
+        let arc = Arc::new(RwLock::new(1));
+        let arc2 = arc.clone();
+        let _: Result<(), _> = thread::spawn(move|| {
+            let _lock = arc2.write().unwrap();
+            panic!();
+        }).join();
+        assert!(arc.read().is_err());
+    }
+
+    #[test]
+    fn test_rw_arc_poison_ww() {
+        let arc = Arc::new(RwLock::new(1));
+        assert!(!arc.is_poisoned());
+        let arc2 = arc.clone();
+        let _: Result<(), _> = thread::spawn(move|| {
+            let _lock = arc2.write().unwrap();
+            panic!();
+        }).join();
+        assert!(arc.write().is_err());
+        assert!(arc.is_poisoned());
+    }
+
+    #[test]
+    fn test_rw_arc_no_poison_rr() {
+        let arc = Arc::new(RwLock::new(1));
+        let arc2 = arc.clone();
+        let _: Result<(), _> = thread::spawn(move|| {
+            let _lock = arc2.read().unwrap();
+            panic!();
+        }).join();
+        let lock = arc.read().unwrap();
+        assert_eq!(*lock, 1);
+    }
+    #[test]
+    fn test_rw_arc_no_poison_rw() {
+        let arc = Arc::new(RwLock::new(1));
+        let arc2 = arc.clone();
+        let _: Result<(), _> = thread::spawn(move|| {
+            let _lock = arc2.read().unwrap();
+            panic!()
+        }).join();
+        let lock = arc.write().unwrap();
+        assert_eq!(*lock, 1);
+    }
+
+    #[test]
+    fn test_rw_arc() {
+        let arc = Arc::new(RwLock::new(0));
+        let arc2 = arc.clone();
+        let (tx, rx) = channel();
+
+        thread::spawn(move|| {
+            let mut lock = arc2.write().unwrap();
+            for _ in 0..10 {
+                let tmp = *lock;
+                *lock = -1;
+                thread::yield_now();
+                *lock = tmp + 1;
+            }
+            tx.send(()).unwrap();
+        });
+
+        // Readers try to catch the writer in the act
+        let mut children = Vec::new();
+        for _ in 0..5 {
+            let arc3 = arc.clone();
+            children.push(thread::spawn(move|| {
+                let lock = arc3.read().unwrap();
+                assert!(*lock >= 0);
+            }));
+        }
+
+        // Wait for children to pass their asserts
+        for r in children {
+            assert!(r.join().is_ok());
+        }
+
+        // Wait for writer to finish
+        rx.recv().unwrap();
+        let lock = arc.read().unwrap();
+        assert_eq!(*lock, 10);
+    }
+
+    #[test]
+    fn test_rw_arc_access_in_unwind() {
+        let arc = Arc::new(RwLock::new(1));
+        let arc2 = arc.clone();
+        let _ = thread::spawn(move|| -> () {
+            struct Unwinder {
+                i: Arc<RwLock<isize>>,
+            }
+            impl Drop for Unwinder {
+                fn drop(&mut self) {
+                    let mut lock = self.i.write().unwrap();
+                    *lock += 1;
+                }
+            }
+            let _u = Unwinder { i: arc2 };
+            panic!();
+        }).join();
+        let lock = arc.read().unwrap();
+        assert_eq!(*lock, 2);
+    }
+
+    #[test]
+    fn test_rwlock_unsized() {
+        let rw: &RwLock<[i32]> = &RwLock::new([1, 2, 3]);
+        {
+            let b = &mut *rw.write().unwrap();
+            b[0] = 4;
+            b[2] = 5;
+        }
+        let comp: &[i32] = &[4, 2, 5];
+        assert_eq!(&*rw.read().unwrap(), comp);
+    }
+
+    #[test]
+    fn test_rwlock_try_write() {
+        let lock = RwLock::new(0isize);
+        let read_guard = lock.read().unwrap();
+
+        let write_result = lock.try_write();
+        match write_result {
+            Err(TryLockError::WouldBlock) => (),
+            Ok(_) => assert!(false, "try_write should not succeed while read_guard is in scope"),
+            Err(_) => assert!(false, "unexpected error"),
+        }
+
+        drop(read_guard);
+    }
+
+    #[test]
+    fn test_into_inner() {
+        let m = RwLock::new(NonCopy(10));
+        assert_eq!(m.into_inner().unwrap(), NonCopy(10));
+    }
+
+    #[test]
+    fn test_into_inner_drop() {
+        struct Foo(Arc<AtomicUsize>);
+        impl Drop for Foo {
+            fn drop(&mut self) {
+                self.0.fetch_add(1, Ordering::SeqCst);
+            }
+        }
+        let num_drops = Arc::new(AtomicUsize::new(0));
+        let m = RwLock::new(Foo(num_drops.clone()));
+        assert_eq!(num_drops.load(Ordering::SeqCst), 0);
+        {
+            let _inner = m.into_inner().unwrap();
+            assert_eq!(num_drops.load(Ordering::SeqCst), 0);
+        }
+        assert_eq!(num_drops.load(Ordering::SeqCst), 1);
+    }
+
+    #[test]
+    fn test_into_inner_poison() {
+        let m = Arc::new(RwLock::new(NonCopy(10)));
+        let m2 = m.clone();
+        let _ = thread::spawn(move || {
+            let _lock = m2.write().unwrap();
+            panic!("test panic in inner thread to poison RwLock");
+        }).join();
+
+        assert!(m.is_poisoned());
+        match Arc::try_unwrap(m).unwrap().into_inner() {
+            Err(e) => assert_eq!(e.into_inner(), NonCopy(10)),
+            Ok(x) => panic!("into_inner of poisoned RwLock is Ok: {:?}", x),
+        }
+    }
+
+    #[test]
+    fn test_get_mut() {
+        let mut m = RwLock::new(NonCopy(10));
+        *m.get_mut().unwrap() = NonCopy(20);
+        assert_eq!(m.into_inner().unwrap(), NonCopy(20));
+    }
+
+    #[test]
+    fn test_get_mut_poison() {
+        let m = Arc::new(RwLock::new(NonCopy(10)));
+        let m2 = m.clone();
+        let _ = thread::spawn(move || {
+            let _lock = m2.write().unwrap();
+            panic!("test panic in inner thread to poison RwLock");
+        }).join();
+
+        assert!(m.is_poisoned());
+        match Arc::try_unwrap(m).unwrap().get_mut() {
+            Err(e) => assert_eq!(*e.into_inner(), NonCopy(10)),
+            Ok(x) => panic!("get_mut of poisoned RwLock is Ok: {:?}", x),
+        }
+    }
+}

ctr-std/src/sys/unix/condvar.rs

@@ -0,0 +1,111 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// *Implementation adapted from `/sys/redox/condvar.rs`
+
+use cell::UnsafeCell;
+use intrinsics::atomic_cxchg;
+use ptr;
+use time::Duration;
+
+use sys::mutex::{self, Mutex};
+
+use libctru::synchronization::{__sync_get_arbiter, LightLock};
+use libctru::svc::{svcArbitrateAddress, ArbitrationType};
+
+pub struct Condvar {
+    lock: UnsafeCell<*mut LightLock>,
+}
+
+unsafe impl Send for Condvar {}
+unsafe impl Sync for Condvar {}
+
+impl Condvar {
+    pub const fn new() -> Condvar {
+        Condvar {
+            lock: UnsafeCell::new(ptr::null_mut()),
+        }
+    }
+
+    #[inline]
+    pub unsafe fn init(&self) {
+        *self.lock.get() = ptr::null_mut();
+    }
+
+    #[inline]
+    pub fn notify_one(&self) {
+        unsafe {
+            let arbiter = __sync_get_arbiter();
+
+            svcArbitrateAddress(arbiter,
+                                *self.lock.get() as u32,
+                                ArbitrationType::ARBITRATION_SIGNAL,
+                                1,
+                                0);
+        }
+    }
+
+    #[inline]
+    pub fn notify_all(&self) {
+        unsafe {
+            let lock = self.lock.get();
+
+            if *lock == ptr::null_mut() {
+                return;
+            }
+
+            let arbiter = __sync_get_arbiter();
+
+            svcArbitrateAddress(arbiter,
+                                *self.lock.get() as u32,
+                                ArbitrationType::ARBITRATION_SIGNAL,
+                                -1,
+                                0);
+        }
+    }
+
+    #[inline]
+    pub fn wait(&self, mutex: &Mutex) {
+        unsafe {
+            let lock = self.lock.get();
+
+            if *lock != mutex::raw(mutex) {
+                if *lock != ptr::null_mut() {
+                    panic!("Condvar used with more than one Mutex");
+                }
+                
+                atomic_cxchg(lock as *mut usize, 0, mutex::raw(mutex) as usize);
+            }
+
+            mutex.unlock();
+
+            let arbiter = __sync_get_arbiter();
+
+            svcArbitrateAddress(arbiter,
+                                *self.lock.get() as u32,
+                                ArbitrationType::ARBITRATION_WAIT_IF_LESS_THAN,
+                                0,
+                                0);
+
+            mutex.lock();
+        }
+    }
+
+    #[inline]
+    pub fn wait_timeout(&self, _mutex: &Mutex, _dur: Duration) -> bool {
+        ::sys_common::util::dumb_print(format_args!("condvar wait_timeout\n"));
+        unimplemented!();
+    }
+
+    #[inline]
+    pub unsafe fn destroy(&self) {
+        *self.lock.get() = ptr::null_mut();
+    }
+}

ctr-std/src/sys/unix/mod.rs

@@ -13,6 +13,7 @@
 use io::{self, ErrorKind};
 use libc;
 
+pub mod condvar;
 pub mod ext;
 pub mod fast_thread_local;
 pub mod fd;
@@ -22,6 +23,8 @@ pub mod mutex;
 pub mod os;
 pub mod os_str;
 pub mod path;
+pub mod rwlock;
+pub mod thread;
 pub mod thread_local;
 pub mod time;
 

ctr-std/src/sys/unix/rwlock.rs

@@ -0,0 +1,61 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use super::mutex::Mutex;
+
+pub struct RWLock {
+    mutex: Mutex
+}
+
+unsafe impl Send for RWLock {}
+unsafe impl Sync for RWLock {}
+
+impl RWLock {
+    pub const fn new() -> RWLock {
+        RWLock {
+            mutex: Mutex::new()
+        }
+    }
+
+    #[inline]
+    pub unsafe fn read(&self) {
+        self.mutex.lock();
+    }
+
+    #[inline]
+    pub unsafe fn try_read(&self) -> bool {
+        self.mutex.try_lock()
+    }
+
+    #[inline]
+    pub unsafe fn write(&self) {
+        self.mutex.lock();
+    }
+
+    #[inline]
+    pub unsafe fn try_write(&self) -> bool {
+        self.mutex.try_lock()
+    }
+
+    #[inline]
+    pub unsafe fn read_unlock(&self) {
+        self.mutex.unlock();
+    }
+
+    #[inline]
+    pub unsafe fn write_unlock(&self) {
+        self.mutex.unlock();
+    }
+
+    #[inline]
+    pub unsafe fn destroy(&self) {
+        self.mutex.destroy();
+    }
+}

ctr-std/src/sys/unix/thread.rs

@@ -0,0 +1,97 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use alloc::boxed::FnBox;
+use libc;
+use cmp;
+use ffi::CStr;
+use io;
+use mem;
+use ptr;
+use sys_common::thread::start_thread;
+use time::Duration;
+
+use libctru::svc::{svcSleepThread, svcGetThreadPriority};
+use libctru::thread::{threadCreate, threadJoin, threadFree};
+use libctru::thread::Thread as ThreadHandle;
+
+pub struct Thread {
+    handle: ThreadHandle,
+}
+
+// Some platforms may have pthread_t as a pointer in which case we still want
+// a thread to be Send/Sync
+unsafe impl Send for Thread {}
+unsafe impl Sync for Thread {}
+
+impl Thread {
+    pub unsafe fn new<'a>(stack: usize, p: Box<FnBox() + 'a>) -> io::Result<Thread> {
+        let p = box p;
+        let stack_size = cmp::max(stack, 0x10000);
+
+        // this retrieves the main thread's priority value. child threads need
+        // to be spawned with a greater priority (smaller priority value) than
+        // the main thread
+        let mut priority = 0;
+        svcGetThreadPriority(&mut priority, 0xFFFF8000);
+        priority -= 1;
+
+        let handle = threadCreate(Some(thread_func), &*p as *const _ as *mut _,
+                                  stack_size, priority, -2, 0);
+
+        return if handle == ptr::null_mut() {
+            Err(io::Error::from_raw_os_error(libc::EAGAIN))
+        } else {
+            mem::forget(p); // ownership passed to the new thread
+            Ok(Thread { handle: handle })
+        };
+
+        extern "C" fn thread_func(start: *mut libc::c_void) {
+            unsafe { start_thread(start) }
+        }
+    }
+
+    pub fn yield_now() {
+        unimplemented!()
+    }
+
+    pub fn set_name(_name: &CStr) {
+        // can't set thread names on the 3DS
+    }
+
+    pub fn sleep(dur: Duration) {
+        unsafe {
+            let nanos = dur.as_secs() * 1_000_000_000 + dur.subsec_nanos() as u64;
+            svcSleepThread(nanos as i64)
+        }
+    }
+
+    pub fn join(self) {
+        unsafe {
+            let ret = threadJoin(self.handle, u64::max_value());
+            threadFree(self.handle);
+            mem::forget(self);
+            debug_assert_eq!(ret, 0);
+        }
+    }
+
+    pub fn id(&self) -> usize {
+        unimplemented!()
+    }
+
+    pub fn into_id(self) -> usize {
+        unimplemented!()
+    }
+}
+
+pub mod guard {
+    pub unsafe fn current() -> Option<usize> { None }
+    pub unsafe fn init() -> Option<usize> { None }
+}

ctr-std/src/sys/unix/time.rs

@@ -106,6 +106,7 @@ impl Ord for Timespec {
 mod inner {
     use fmt;
     use libc;
+    use sync::Once;
     use sys::cvt;
     use sys_common::mul_div_u64;
     use time::Duration;
@@ -113,7 +114,6 @@ mod inner {
     use super::NSEC_PER_SEC;
     use super::Timespec;
 
-    use spin;
     use libctru;
 
     #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]
@@ -164,7 +164,7 @@ mod inner {
     }
 
     // The initial system tick after which all Instants occur
-    static TICK: spin::Once<u64> = spin::Once::new();
+    static mut TICK: u64 = 0;
 
     // A source of monotonic time based on ticks of the 3DS CPU. Returns the
     // number of system ticks elapsed since an arbitrary point in the past
@@ -180,7 +180,13 @@ mod inner {
     // subsequent calls to this function return the previously generated
     // tick value
     fn get_first_tick() -> u64 {
-        *TICK.call_once(get_system_tick)
+        static ONCE: Once = Once::new();
+        unsafe { 
+            ONCE.call_once(|| {
+                TICK = get_system_tick();
+            });
+            TICK
+        }
     }
 
     // Gets the current system tick
@@ -201,11 +207,12 @@ mod inner {
     // on a New 3DS running in 804MHz mode
     //
     // See https://www.3dbrew.org/wiki/Hardware#Common_hardware
-    fn info() -> CtrClockInfo {
+    fn info() -> &'static CtrClockInfo {
-        CtrClockInfo {
+        static INFO: CtrClockInfo = CtrClockInfo {
             numer: 1_000_000_000,
             denom: 268_111_856,
-        }
+        };
+        &INFO
     }
 
     fn dur2intervals(dur: &Duration) -> u64 {

ctr-std/src/sys_common/condvar.rs

@@ -0,0 +1,70 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use time::Duration;
+use sys_common::mutex::{self, Mutex};
+use sys::condvar as imp;
+
+/// An OS-based condition variable.
+///
+/// This structure is the lowest layer possible on top of the OS-provided
+/// condition variables. It is consequently entirely unsafe to use. It is
+/// recommended to use the safer types at the top level of this crate instead of
+/// this type.
+pub struct Condvar(imp::Condvar);
+
+impl Condvar {
+    /// Creates a new condition variable for use.
+    ///
+    /// Behavior is undefined if the condition variable is moved after it is
+    /// first used with any of the functions below.
+    pub const fn new() -> Condvar { Condvar(imp::Condvar::new()) }
+
+    /// Prepares the condition variable for use.
+    ///
+    /// This should be called once the condition variable is at a stable memory
+    /// address.
+    #[inline]
+    pub unsafe fn init(&mut self) { self.0.init() }
+
+    /// Signals one waiter on this condition variable to wake up.
+    #[inline]
+    pub unsafe fn notify_one(&self) { self.0.notify_one() }
+
+    /// Awakens all current waiters on this condition variable.
+    #[inline]
+    pub unsafe fn notify_all(&self) { self.0.notify_all() }
+
+    /// Waits for a signal on the specified mutex.
+    ///
+    /// Behavior is undefined if the mutex is not locked by the current thread.
+    /// Behavior is also undefined if more than one mutex is used concurrently
+    /// on this condition variable.
+    #[inline]
+    pub unsafe fn wait(&self, mutex: &Mutex) { self.0.wait(mutex::raw(mutex)) }
+
+    /// Waits for a signal on the specified mutex with a timeout duration
+    /// specified by `dur` (a relative time into the future).
+    ///
+    /// Behavior is undefined if the mutex is not locked by the current thread.
+    /// Behavior is also undefined if more than one mutex is used concurrently
+    /// on this condition variable.
+    #[inline]
+    pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
+        self.0.wait_timeout(mutex::raw(mutex), dur)
+    }
+
+    /// Deallocates all resources associated with this condition variable.
+    ///
+    /// Behavior is undefined if there are current or will be future users of
+    /// this condition variable.
+    #[inline]
+    pub unsafe fn destroy(&self) { self.0.destroy() }
+}

ctr-std/src/sys_common/mod.rs

@@ -25,11 +25,16 @@
 #![allow(missing_docs)]
 
 pub mod at_exit_imp;
+pub mod condvar;
 pub mod io;
 pub mod mutex;
 pub mod poison;
 pub mod remutex;
+pub mod rwlock;
+pub mod thread;
+pub mod thread_info;
 pub mod thread_local;
+pub mod util;
 
 // common error constructors
 

ctr-std/src/sys_common/rwlock.rs

@@ -0,0 +1,82 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use sys::rwlock as imp;
+
+/// An OS-based reader-writer lock.
+///
+/// This structure is entirely unsafe and serves as the lowest layer of a
+/// cross-platform binding of system rwlocks. It is recommended to use the
+/// safer types at the top level of this crate instead of this type.
+pub struct RWLock(imp::RWLock);
+
+impl RWLock {
+    /// Creates a new reader-writer lock for use.
+    ///
+    /// Behavior is undefined if the reader-writer lock is moved after it is
+    /// first used with any of the functions below.
+    pub const fn new() -> RWLock { RWLock(imp::RWLock::new()) }
+
+    /// Acquires shared access to the underlying lock, blocking the current
+    /// thread to do so.
+    ///
+    /// Behavior is undefined if the rwlock has been moved between this and any
+    /// previous method call.
+    #[inline]
+    pub unsafe fn read(&self) { self.0.read() }
+
+    /// Attempts to acquire shared access to this lock, returning whether it
+    /// succeeded or not.
+    ///
+    /// This function does not block the current thread.
+    ///
+    /// Behavior is undefined if the rwlock has been moved between this and any
+    /// previous method call.
+    #[inline]
+    pub unsafe fn try_read(&self) -> bool { self.0.try_read() }
+
+    /// Acquires write access to the underlying lock, blocking the current thread
+    /// to do so.
+    ///
+    /// Behavior is undefined if the rwlock has been moved between this and any
+    /// previous method call.
+    #[inline]
+    pub unsafe fn write(&self) { self.0.write() }
+
+    /// Attempts to acquire exclusive access to this lock, returning whether it
+    /// succeeded or not.
+    ///
+    /// This function does not block the current thread.
+    ///
+    /// Behavior is undefined if the rwlock has been moved between this and any
+    /// previous method call.
+    #[inline]
+    pub unsafe fn try_write(&self) -> bool { self.0.try_write() }
+
+    /// Unlocks previously acquired shared access to this lock.
+    ///
+    /// Behavior is undefined if the current thread does not have shared access.
+    #[inline]
+    pub unsafe fn read_unlock(&self) { self.0.read_unlock() }
+
+    /// Unlocks previously acquired exclusive access to this lock.
+    ///
+    /// Behavior is undefined if the current thread does not currently have
+    /// exclusive access.
+    #[inline]
+    pub unsafe fn write_unlock(&self) { self.0.write_unlock() }
+
+    /// Destroys OS-related resources with this RWLock.
+    ///
+    /// Behavior is undefined if there are any currently active users of this
+    /// lock.
+    #[inline]
+    pub unsafe fn destroy(&self) { self.0.destroy() }
+}

ctr-std/src/sys_common/thread.rs

@@ -0,0 +1,22 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use alloc::boxed::FnBox;
+use libc;
+//use sys::stack_overflow;
+
+pub unsafe fn start_thread(main: *mut libc::c_void) {
+    // Next, set up our stack overflow handler which may get triggered if we run
+    // out of stack.
+    // let _handler = stack_overflow::Handler::new();
+
+    // Finally, let's run some code.
+    Box::from_raw(main as *mut Box<FnBox()>)()
+}

ctr-std/src/sys_common/thread_info.rs

@@ -0,0 +1,61 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(dead_code)] // stack_guard isn't used right now on all platforms
+
+use cell::RefCell;
+use thread::Thread;
+use thread::LocalKeyState;
+
+struct ThreadInfo {
+    stack_guard: Option<usize>,
+    thread: Thread,
+}
+
+thread_local! { static THREAD_INFO: RefCell<Option<ThreadInfo>> = RefCell::new(None) }
+
+impl ThreadInfo {
+    fn with<R, F>(f: F) -> Option<R> where F: FnOnce(&mut ThreadInfo) -> R {
+        if THREAD_INFO.state() == LocalKeyState::Destroyed {
+            return None
+        }
+
+        THREAD_INFO.with(move |c| {
+            if c.borrow().is_none() {
+                *c.borrow_mut() = Some(ThreadInfo {
+                    stack_guard: None,
+                    thread: NewThread::new(None),
+                })
+            }
+            Some(f(c.borrow_mut().as_mut().unwrap()))
+        })
+    }
+}
+
+pub fn current_thread() -> Option<Thread> {
+    ThreadInfo::with(|info| info.thread.clone())
+}
+
+pub fn stack_guard() -> Option<usize> {
+    ThreadInfo::with(|info| info.stack_guard).and_then(|o| o)
+}
+
+pub fn set(stack_guard: Option<usize>, thread: Thread) {
+    THREAD_INFO.with(|c| assert!(c.borrow().is_none()));
+    THREAD_INFO.with(move |c| *c.borrow_mut() = Some(ThreadInfo{
+        stack_guard: stack_guard,
+        thread: thread,
+    }));
+}
+
+// a hack to get around privacy restrictions; implemented by `std::thread`
+pub trait NewThread {
+    fn new(name: Option<String>) -> Self;
+}

ctr-std/src/sys_common/util.rs

@@ -0,0 +1,49 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use fmt;
+use io::prelude::*;
+use sync::atomic::{self, Ordering};
+use sys::stdio::Stderr;
+
+pub fn min_stack() -> usize {
+    static MIN: atomic::AtomicUsize = atomic::AtomicUsize::new(0);
+    match MIN.load(Ordering::SeqCst) {
+        0 => {}
+        n => return n - 1,
+    }
+
+	// NOTE: We don't have env variable support on the 3DS so let's just use the
+	// default minimum
+
+    // let amt = env::var("RUST_MIN_STACK").ok().and_then(|s| s.parse().ok());
+    // let amt = amt.unwrap_or(2 * 1024 * 1024);
+
+	let amt = 2 * 1024 * 1024;
+
+    // 0 is our sentinel value, so ensure that we'll never see 0 after
+    // initialization has run
+    MIN.store(amt + 1, Ordering::SeqCst);
+    amt
+}
+
+pub fn dumb_print(args: fmt::Arguments) {
+    let _ = Stderr::new().map(|mut stderr| stderr.write_fmt(args));
+}
+
+// Other platforms should use the appropriate platform-specific mechanism for
+// aborting the process.  If no platform-specific mechanism is available,
+// ::intrinsics::abort() may be used instead.  The above implementations cover
+// all targets currently supported by libstd.
+
+pub fn abort(args: fmt::Arguments) -> ! {
+    dumb_print(format_args!("fatal runtime error: {}\n", args));
+    unsafe { ::sys::abort_internal(); }
+}