Swapped out pthread_rwlock_xxlock(), which doesn't return if it can't obtain...

Swapped out pthread_rwlock_xxlock(), which doesn't return if it can't obtain the lock, with pthread_rwlock_xxtrylock() followed by sched yield and error code return. The issue is sometimes a thread calling pthread_cond_init() or pthread_cond_destroy() can't acquire the lock when another thread is waiting on a condition variable notification via pthread_cond_timedwait(), and thus the thread calling pthread_cond_init() or pthread_cond_destroy() end up hanging indefinitely.