mbed-os/libraries/tests/rtos/mbed/mutex/main.cpp

#include "mbed.h"
#include "test_env.h"
#include "rtos.h"

#define THREAD_DELAY     50
#define SIGNALS_TO_EMIT  100

void print_char(char c = '*')
{
    printf("%c", c);
    fflush(stdout);
}

Mutex stdio_mutex;
DigitalOut led(LED1);

volatile int change_counter = 0;
volatile bool changing_counter = false;

bool manipulate_protected_zone(const int thread_delay) {
    bool result = true;

    stdio_mutex.lock(); // LOCK
    if (changing_counter == true) {
        print_char('e');    // if changing_counter is true access is not exclusively
        result = false;
        notify_completion(false);
        exit(1);
    }
    changing_counter = true;

    // Some action on protected
    led = !led;
    change_counter++;
    print_char('.');
    Thread::wait(thread_delay);

    changing_counter = false;
    stdio_mutex.unlock();   // UNLOCK
    return result;
}

void test_thread(void const *args) {
    const int thread_delay = int(args);
    while (true) {
        manipulate_protected_zone(thread_delay);
    }
}

int main() {
    const int t1_delay = THREAD_DELAY * 1;
    const int t2_delay = THREAD_DELAY * 2;
    const int t3_delay = THREAD_DELAY * 3;
    Thread t2(test_thread, (void *)t2_delay);
    Thread t3(test_thread, (void *)t3_delay);
    bool result = true;

    while (true) {
        // Thread 1 action
        Thread::wait(t1_delay);
        manipulate_protected_zone(t1_delay);
        if (change_counter >= SIGNALS_TO_EMIT) {
            break;
        }
    }

    notify_completion(result);
    return 0;
}