pthread_mutex_lock.c:62: __pthread_mutex_lock: Assertion `mutex->__data.__owner == 0' failed

Question

I received that error:

pthread_mutex_lock.c:62: __pthread_mutex_lock: Assertion `mutex->_data._owner == 0' failed.

And I cannot found any cause of that. However I'm not sure about the following piece of code:

Declarations:

std::mutex lock;
std::condition_variable cond;

Sequence of locks & unlocks:

std::unique_lock<std::mutex> lk(lock);

cond.wait(lk);

lock.unlock();

If I remove this sequence - everything works fine, but without any protection. I'm not sure if I use unique_lock properly.

Answer 1

std::unique_lock and the other locks acquire a mutex in constructor and releases it in destructor. You called lock.unlock() in your code manually, making it being called effectively twice.

After removing that statement your code should work properly.