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Both Condition and Mutex

Question Text​

Can we only use a mutex when signalling an event from one thread to another in?

Question Answers​

  • No, because this would imply that the signalling thread would unlock() the mutex, that the signalled thread attempts to lock(), which is an undefined behaviour

  • No, because it will result in a deadlock where the both threads will be waiting for each other

  • Yes, because only one thread can modify the shared variables in order to maintain their integrity

  • Yes and this would yield better performance because the threads would only wait for one object: the mutex

Feedback​

In some implementations, such as POSIX threads (pthreads), calling unlock() from another thread than that which called lock() can result in an undefined behaviour. For this reason, it is unsafe to only use a mutex as a notification mechanism. In addition, a mutex cannot notify more than one thread at once, if we so desire. Mutexes are only meant to be used to isolate a critical section within the same thread.