pthread_mutex_timedlock(3) on FreeBSD
The text cfec936f39ec, as FreeBSD 6.3-RELEASE, FreeBSD 6.2-RELEASE, FreeBSD 6.1-RELEASE, FreeBSD 6.0-RELEASE, FreeBSD 5.5-RELEASE, FreeBSD 5.4-RELEASE, FreeBSD 5.3-RELEASE shipped it.
lock a mutex without blocking indefinitely