C++ 互斥锁的所有权不会转移到另一个线程 当读卡器得到锁时

输出与我预期的不同

我所期望的是作者和读者交替拥有锁

这种行为正常吗

---

是否有锁定机构的偏好？i、 e.

共享锁

优于

升级锁

问题在于，当另一个读写器抓取互斥锁时，读写器都无法轻松克服紧密循环。看看你的要点：

锁互斥

睡眠

释放互斥

转到步骤1

第3步之后的窗口是读写器获取互斥锁的唯一机会。这个窗口很短，所以它抓住它的机会很小。这就是为什么您只能看到写入程序或读卡器打印到控制台。事实上，如果你永远等待，你很可能会看到不同的实体将获得工作的机会

那么如何修复它呢？这很简单：只需将睡眠从锁中移出，如下所示：

writerreader0started
reader3startedreader
0: Got the lock
0reader2reader3: Got the lock
reader1started
reader1: Got the lock
started
started
reader2: Got the lock
reader0: Got the lock
reader3: Got the lock
reader1: Got the lock
reader2: Got the lock
reader1: Got the lock
reader2: Got the lock
reader0: Got the lock
reader3: Got the lock
readerreader3: Got the lock
reader2: Got the lock
0: Got the lock

void编写器（int-id）
{
cerr“问题是，一旦编写器拥有互斥体或读卡器拥有互斥体，owernership就不会转移到它的相反线程（readers->writer/writer->readers）”这难道不是互斥体的全部用途吗（互斥）同步机制是关于？？你的意思是实现一个吗？我想这已经可以从当前的c+标准BTW中获得。不需要使用boost。
writer0started
readerwriterreader0: Got the lock
readerreader21started30started
started

started
writer0: Got the lock
writer0: Got the lock
writer0: Got the lock
writer0: Got the lock
writer0: Got the lock

writerreader0started
reader3startedreader
0: Got the lock
0reader2reader3: Got the lock
reader1started
reader1: Got the lock
started
started
reader2: Got the lock
reader0: Got the lock
reader3: Got the lock
reader1: Got the lock
reader2: Got the lock
reader1: Got the lock
reader2: Got the lock
reader0: Got the lock
reader3: Got the lock
readerreader3: Got the lock
reader2: Got the lock
0: Got the lock

void writer(int id)
{
    cerr << "writer" << id << "started" << endl;
    while(gSignalStatus) {
        {
            boost::upgrade_lock<boost::shared_mutex> lock(g_mutex);
            boost::upgrade_to_unique_lock<boost::shared_mutex> unique_lock(lock);
            cout << "writer" << id << ": Got the lock" << endl;
        }
        boost::this_thread::sleep(boost::posix_time::milliseconds(200));
    }
}

void reader(int id)
{
    cerr << "reader" << id << "started" << endl;
    while(gSignalStatus) {
        {
            boost::shared_lock<boost::shared_mutex> lock(g_mutex);
            cerr << "reader" << id << ": Got the lock" << endl;
        }
        boost::this_thread::sleep(boost::posix_time::milliseconds(200));
    }
}