Description

   The sem_timedwait function locks the semaphore referenced by
   sem as in the sem_wait function. But if the semaphore cannot be
   locked without waiting for another process or thread to unlock
   the semaphore by performing a sem_post function, this wait
   terminates when the specified timeout expires.

   The timeout expires when the absolute time specified by abs_
   timeout passes, as measured by the clock on which timeouts are
   based (that is, when the value of that clock equals or exceeds
   abs_timeout, or if the absolute time specified by abs_timeout has
   already been passed at the time of the call.

   The function will not fail with a timeout if the semaphore can be
   locked immediately. The validity of abs_timeout does not need to
   be checked if the semaphore can be locked immediately.