Tue, 31 Mar 2009 15:37:33 +0200, Stefan Rohe wrote: > could someone explain us this "synchronize" behaviour? We do not understand > it. > > Two Threads. > First Thread should wait for a condition. This we do in a > synchronized(mutex) block. > The second Thread broadcasts then a notify. This also in a synchronized > block, synchronizing on the same mutex. This should be impossible!? Does the > condition.wait modify the Mutex object so that it after this has another > address?
The whole point of a condition variable is to allow other threads to acquire the same mutex while you're waiting. What happens is the mutex associated with the conditional variable is unlocked the same instant you start waiting on that variable. When the other thread notifies you, the cond var attempts to lock the mutex again and therefore waits until the other thread either leaves the critical section or starts waiting itself.