2008 April 11th Friday (四月 十一日 金曜日）

This week there are three weddings at our departments.  Oh, Olympic year!!!     pthread_cond_wait atomically unlocks  the  mutex  (as  per pthread_unlock_mutex) and waits for the condition variable cond to be signaled. The thread execution is suspended and does not consume any CPU time until the condition variable is signaled. The mutex  must  be  locked  by  the  calling thread on entrance to pthread_cond_wait. Before returning to the calling thread, pthread_cond_wait re-acquires mutex (as per pthread_lock_mutex).   Unlocking  the mutex and suspending on the condition variable is done  atomically.  Thus, if all threads always acquire the mutex before signaling the condition, this guarantees that the condition cannot be signaled (and thus ignored) between the time a thread locks the mutex and the time it waits on the condition variable.