Fix deadlocks in cipher ctr mt #7
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added 4 commits
September 7, 2016 11:40
…ES-CTR cipher The threads spend a lot of time in pthread_cond_wait waiting for the state of a queue to change, but sometimes a thread will change the state of a queue without notifying other threads. This makes sure other threads will always get notified to avoid deadlocks. This uses pthread_cond_broadcast rather than pthread_cond_signal since pthread_cond_signal only notifies one thread, which could end up being the parent thread, which will just loop back to the cond, and nothing will continue.
There is no gurantee that pthread_create will have filled in the thread id field when the thread starts, so there was a race condition. Sometimes the first thread would see c->tid[0] as 0, and not initialize the first queue, and the entire thing would deadlock. This uses a rwlock to make sure that the tid is filled in before trying to access it.
Currently it's possible that the other threads will transition the first queue to another state than KQDRAINING before the starting thread gets woken up, and if the queue never goes back to KQDRAINING then the init thread will never continue.
…y are cancelled It seems that on OSX a pthread_cancel does not necessarily wake up a thread that is in pthread_cond_wait. This results in the process hanging indefinetly when the main thread does a pthread_join on a thread that is sleeping. This adds an explicit call to pthread_cond_broadcast to every queue's condition so all the threads get woken up after they are cancelled.
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