[提问]请教关于QMutex的用法？？ [复制链接]

如果有两个函数fun1,和fun2，分别在两个线程中调用，是不是必须在两个函数中同时加锁才有用，如果只在一个线程中加锁会怎么样？
比如： int d = 0;


QMutex mutex;


void fun1(int& d)
{
  mutex.lock();
  d += 5;
  d /= 4;
  mutex.unlock();
}

void fun2(int& d)
{
  mutex.lock(); //如果将此处注释掉会怎么样？
  d *= 2;
  d -= 2;
  mutex.unlock();//如果将此处注释掉会怎么样？
}

难道就没有一个人能说说吗？？

lock和unlock必须配对使用，如果没有unlock，这个mutex会被锁住，想要lock的其它线程就会卡住，一直等待mutex被unlock。

Locks the mutex. If another thread has locked the mutex then this call will block until that thread has unlocked it.
Calling this function multiple times on the same mutex from the same thread is allowed if this mutex is a recursive mutex. If this mutex is a non-recursive mutex, this function will dead-lock when the mutex is locked recursively


Unlocking a mutex that is not locked results in undefined behavior.