pthread_cond_timedwait gives a timestamp as the timeout, but libctru
expects a duration. After converting the timestamp to nanoseconds since
epoch, we were telling libctru to sleep for over 52 years!
This commit changes our impl to convert the timestamp to a duration.
Additionally, CondVar_WaitTimeout returns a boolean indicating if it
timed out or not. But pthread_cond_timedwait expects a libc-style error
code. This conversion is added as well.
The standard library RwLock checks if it's panicking while making the
guard. This check needs to use a thread local key, which it lazily
creates. This causes reentrant/recursive locking, which leads to a
deadlock.
This commit replaces the std RwLock with one from spin, which does not
need to check thread local storage to lock. It's a spin-lock, but it is
configured to yield the thread on every unsuccessful spin. Also, the
lock can be created statically, which means we don't need once_cell.
An alternative to spin is parking_lot, but that has some compile errors
(it wants condvars to support monotonic clocks) and brings in more
dependencies.
Ian Chamberlain