2000-01-03 Kaz Kylheku <kaz@ashi.footprints.net>
Redesigned how cancellation unblocks a thread from internal
cancellation points (sem_wait, pthread_join,
pthread_cond_{wait,timedwait}).
Cancellation won't eat a signal in any of these functions
(*required* by POSIX and Single Unix Spec!).
* condvar.c: spontaneous wakeup on pthread_cond_timedwait won't eat a
simultaneous condition variable signal (not required by POSIX
or Single Unix Spec, but nice).
* spinlock.c: __pthread_lock queues back any received restarts
that don't belong to it instead of assuming ownership of lock
upon any restart; fastlock can no longer be acquired by two threads
simultaneously.
* restart.h: restarts queue even on kernels that don't have
queued real time signals (2.0, early 2.1), thanks to atomic counter,
avoiding a rare race condition in pthread_cond_timedwait.
