How to give priority to privileged thread in mutex locking?

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失恋的感觉 2020-12-01 02:48

First of all: I am completely a newbie in mutex/multithread programming, so sorry for any error in advance...

I have a program that runs multiple threads. The threads

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既然无缘 (楼主)

2020-12-01 03:42

Try something like the following. You could make the class a thread-safe singleton and you could even make it a functor.

#include 
#include 
#include 

class ThreadPrioFun
{
    typedef std::multimap priomap_t;
public:
    ThreadPrioFun()
    {
        pthread_mutex_init(&mtx, NULL);
    }
    ~ThreadPrioFun()
    {
        pthread_mutex_destroy(&mtx);
    }
    void fun(int prio, sem_t* pSem)
    {
        pthread_mutex_lock(&mtx);
        bool bWait = !(pm.empty());
        priomap_t::iterator it = pm.insert(std::pair(prio, pSem) );
        pthread_mutex_unlock(&mtx);

        if( bWait ) sem_wait(pSem);

        // do the actual job
        // ....
        //

        pthread_mutex_lock(&mtx);
        // done, remove yourself
        pm.erase(it);
        if( ! pm.empty() )
        {
             // let next guy run:
            sem_post((pm.begin()->second));
        }
        pthread_mutex_unlock(&mtx);
    }
private:
    pthread_mutex_t mtx;
    priomap_t pm;
};

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