EXC_BAD_INSTRUCTION.m

    dispatch_semaphore_t semaphore = dispatch_semaphore_create(1);

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        sleep(1);
        dispatch_semaphore_signal(semaphore);
        sleep(1);
        dispatch_semaphore_signal(semaphore);
        sleep(1);
        dispatch_semaphore_signal(semaphore);
    });
    
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    NSLog(@"Start");
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    NSLog(@"1");
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    NSLog(@"2");
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    NSLog(@"3");
    
    dispatch_release(semaphore);

OK.m

    dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
    dispatch_semaphore_signal(semaphore);

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        sleep(1);
        dispatch_semaphore_signal(semaphore);
        sleep(1);
        dispatch_semaphore_signal(semaphore);
        sleep(1);
        dispatch_semaphore_signal(semaphore);
    });
    
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    NSLog(@"Start");
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    NSLog(@"1");
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    NSLog(@"2");
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    NSLog(@"3");
    
    dispatch_release(semaphore);