c++multithreadingsynchronizationshared-state

Two threads using a same variable

I have two threads: 'main' and 'worker', and one global variable bool isQuitRequested that will be used by the main thread to inform worker, when it's time to quit its while loop (something like this: while(isQuitRequested == false) { ... do some stuff ... })

Now, I'm a bit concerned... Do I need to use some kind of mutex protection for isQuitRequested, considering that only one thread (main) performs isQuitRequested = true operation, and the other (worker) just performs checking and nothing else?

I have read What could happen if two threads access the same bool variable at the same time?. I'ts something similar, but not the same situation...

Solution

  • You have not specified which language you are using and from the small code snippet that you posted it could be either C#, Java or C++. Here are some common solutions for this "pattern" for each of them:

    C#: 

    volatile bool isQuitRequested;

    Java:

    volatile boolean isQuitRequested;

    C++: volatile in C++ is not nearly as useful. Go with:

    std::atomic<bool> isQuitRequested;