C++ pthread blocking queue deadlock (I think)

Question

I am having a problem with pthreads where i think i am getting a deadlock. I have created a blocking queue which I thought was working, but after doing some more testing I h

Answer 1

I've had similar experience with pthread_cond_wait() / pthread_cancel(). I had issues with a lock still being held after the thread returned for some reason, and it was impossible to unlock it, since you have to unlock in the same thread as you locked. I noticed these errors when doing pthread_mutex_destroy() since I had a single producer, single consumer situation so the deadlock didn't occur.

pthread_cond_wait() is supposed to lock the mutex when returning, and this could have happened, but the final unlock didn't go through since we forcefully canceled the thread. For safety I generally try to avoid using pthread_cancel() altogether since some platforms don't even support this. You could use a volatile bool or atomics and check if thread should be shut down. That way, the mutexes will be handled cleanly as well.