stupid_threads.cpp

bool thread2_is_waiting_for_sync = false;


auto mutex  = PTHREAD_MUTEX_INITIALIZER;
auto cond_m = PTHREAD_MUTEX_INITIALIZER;
auto cond   = PTHREAD_COND_INITIALIZER ;

void* thread1(void*) {
    
    mutex  = PTHREAD_MUTEX_INITIALIZER;
    cond_m = PTHREAD_MUTEX_INITIALIZER;
    cond   = PTHREAD_COND_INITIALIZER ;
    assert(!pthread_mutex_lock(&mutex));
    
    pthread_create(&thread_handle, NULL, thread2, NULL);
    
    for(;;) {
        
        // ...
        
        if (thread2_is_waiting_for_sync) {
            
            assert(!pthread_mutex_unlock(&mutex));
            
            assert(!pthread_mutex_lock(&cond_m));
            while (thread2_is_waiting_for_sync) {
                assert(!pthread_cond_wait(&cond, &cond_m));
            }
            assert(!pthread_mutex_unlock(&cond_m));
            
            assert(!pthread_mutex_lock(&mutex));
            
        }
        // ...
    }
}



void* thread1(void*) {
    
    for (;;) {
        block_on_something_for_a_long_time();
        
        assert(!pthread_mutex_lock(&cond_m));
        thread2_is_waiting_for_sync = true;
        assert(!pthread_mutex_unlock(&cond_m));
        
        assert(!pthread_mutex_lock(&mutex));
        assert(!pthread_mutex_lock(&cond_m));
        
        // Do stuff with thread1's data...
        
        thread2_is_waiting_for_sync = false;
        
        assert(!pthread_cond_broadcast(&cond));
        assert(!pthread_mutex_unlock(&cond_m));
        assert(!pthread_mutex_unlock(&mutex));
    }
}