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[mynickmynick]

From the following source code

int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
{
volatile pthread_descr self = thread_self();

__pthread_lock(&cond->__c_lock, self);
enqueue(&cond->__c_waiting, self);
__pthread_unlock(&cond->__c_lock);
pthread_mutex_unlock(mutex);
suspend_with_cancellation(self);
pthread_mutex_lock(mutex);
/* This is a cancellation point */
if (THREAD_GETMEM(self, p_canceled)
&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
/* Remove ourselves from the waiting queue if we're still on it */
__pthread_lock(&cond->__c_lock, self);
remove_from_queue(&cond->__c_waiting, self);
__pthread_unlock(&cond->__c_lock);
pthread_exit(PTHREAD_CANCELED);
}
return 0;
}

it seems that when a thread gets canceled while waiting for cond it performs
pthread_mutex_lock(mutex);
...
pthread_exit(PTHREAD_CANCELED);

and leaves mutex locked?!
so anothe thread is potentially deadlocked?!
I tried to look in the source for pthread_exit() if and when the mutex is released but I didn't figure out!


So may be to prevent this the correct usage is

  pthread_mutex_lock(mutex);

  pthread_cleanup_push(pthread_mutex_unlock,mutex);

  while (...) pthread_cond_wait(cond,mutex); 

......

  pthread_cleanup_pop();

  pthread_mutex_unlock(mutex);

what you think?

Edited by mynickmynick, 08 May 2008 - 05:55 AM.