Question

For the below C++ code

volatile bool keepRunning = true;

void run() {
    while (keepRunning) {
        doSomeWork();
    }
}

void stop() {
    keepRunning = false;
}

suppose one thread executes stop() and multiple threads are executing run()

I believe this kind of construct (one writer, no synchronization primitives) is quite prevalent in embedded systems. Is this guaranteed to work, assuming there’s no multiple processors/cores?

Thanks

Answer 1

Yes, because on a unicore machine there is only one CPU and one CPU-cache.

Another reason: To the CPU, it looks like there is only one thread running. The CPU is obliged to present the application a view of memory which is equivalent to single-threaded execution because the CPU can’t even tell that there are multiple threads.