Subj : CondVar on Windows : what to do when a consumer thread is killed
To   : comp.programming.threads
From : adebaene
Date : Fri Jul 01 2005 03:09 am

Hello all,

I am using an implementation of condvars on Win32 based on the one that
is described here : http://www.cs.wustl.edu/~schmidt/win32-cv-1.html.
(I am using the 3.4 solution : the one using SignalAndWait). It works
great (at least for my needs) except in one situation :

Say I have only 1 thread holding the condvar (blocked calling
pthread_cond_wait). If this thread is killed, the waiters_count "leaks"
(waiters_count==1 while there is no waiters left).

If, after that, another thread try to call pthread_cond_broadcast, it
will block forecever waiting on the " WaitForSingleObject
(cv->waiters_done_, INFINITE);" line inside this function, because no
thread will ever set the waiters_done event.

Does anyone have a solution to detect this situation and avoid the
deadlock? I thought about having a timeout on
WaitForSingleObject(waiters_done), but I don't know what value to give
to this timeout, and even like that, what to do in case of timeout,
since the semaphore has already been released and I've got no idea of
the state of awaiting threads.

What does Posix says on behaviour of a condvar whenever a waiting
thread is killed?

Thanks,

Arnaud

.