c++ - QMutex 是否需要是静态的，以便此类实例的其他线程调用知道暂停其操作？

Question

从多个线程调用以下附加函数。我不希望数据重写追加，因为计数器尚未增加。

除了当前使用 Append 的线程之外，这是否会暂停所有进入的线程？或者其他线程会继续运行而不附加数据吗？

互斥体是否需要“静态”或每个实例都知道暂停操作？

如果我不想打嗝，我假设我必须建立一个缓冲区来备份日志数据？

void classA::Append(int _msg)
{
    static int c = 0;
    QMutex mutex; //need to be static so other threads know to suspend?
                  //there are 10 threads creating an instantiation of classA or an object of classA     

    mutex.lock();

    intArray[c] = _msg;
    c++;

    mutex.unlock();
}

Answer 1

不，它不需要static，只需让它成为您的成员，您classA还可以查看QMutexLocker来锁定和解锁互斥锁：

void classA::Append(int _msg)
{
    static int c = 0;
    QMutexLocker locker(&mutex); // mutex is a QMutex member in your class

    intArray[c] = _msg;
    c++;

    /*mutex.unlock(); this unlock is not needed anymore, because QMutexLocker unlocks the mutex when the locker scope ends, this very useful especially if you have conditional and return statements in your function*/
}

Answer 2

QMutex 不需要声明为静态，Qt 将确保其他线程将等待直到互斥锁上发生解锁，然后才允许另一个线程继续在该函数中执行。

Answer 3

为了解决我的问题，在多次运行后，由于 classA 的多个实例化，我确实不得不将互斥锁设为“静态”。使互斥锁成为成员不起作用。

void classA::Append(int _msg)
{
    static int c = 0;
    static QMutex mutex; //YES... need to be static so other threads know to suspend
                         //there are 10 threads creating an instantiation of classA or an object of classA     

    mutex.lock();

    intArray[c] = _msg;
    c++;

    mutex.unlock();
}

Answer 4

@jdl“使互斥锁成为成员不起作用”。是的，它有效。尝试像这样使互斥锁“静态”：

//classA.h
class ClassA {
    public:
        static QMutex mutex;
        // rest of variables and Methods
        // ...
}


//classA.cpp
QMutex ClassA::mutex; // Before all
ClassA::ClassA() {
    //Constructor
}
void ClassA::Append(int _msg) {
    static int c = 0
    QMutexLocker locker(&mutex)
    intArray[c] = _msg;
    c++;
}

Answer 5

由于我不知道 QMutex 是如何真正运行的，所以我只是做了自己的互斥锁。

void classA::Append(int _msg)
{
    static int c = 0;
    static int mutex = 0; //YES... need to be static so other threads know to suspend
                     //there are 10 threads creating an instantiation of classA or an object of classA     

    while(mutex == 1){
        //suspend thread
    }

    if(mutex == 0){
        mutex = 1;//lock        

        intArray[c] = _msg;
        c++;

        mutex = 0;//unlock
    }

}