CLRviaC#读书笔记3-4锁-条件变量模式

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条件变量模式(The Condition variable Pattern)

指的是一个任务在等待一个变量的状态.(例如一个线程当变量为true的时候执行,否则就一直在休眠状态)

以下代码演示了Thread1 一直在等待m_condition的状态

Thread1在等待状态改变的过程中,间歇性的暂时释放锁的控制权

这样Thread2就有机会获得到锁,改变m_condition的状态,并且执行Pulse(All)方法, 该方法将在执行Mointor.Exit(m_lock)的时候唤醒所有等待者,此时等待者发现状态已经改变,那么就开始执行相应的业务逻辑

代码


internal sealed class ConditionVariablePattern
{
private readonly Object m_lock = new Object();
private Boolean m_condition = false;
public void Thread1()
    {
        Monitor.Enter(m_lock); // Acquire a mutual-exclusive lock
// While under the lock, test the complex condition "atomically"
        while (!m_condition)
        {
// If condition is not met, wait for another thread to change the condition
            Monitor.Wait(m_lock); // Temporarily release lock so other threads can get it
        }
// The condition was met, process the data...
        Monitor.Exit(m_lock); // Permanently release lock
    }
public void Thread2()
    {
        Monitor.Enter(m_lock); // Acquire a mutual-exclusive lock
// Process data and modify the condition...
        m_condition = true;
// Monitor.Pulse(m_lock); // Wakes one waiter AFTER lock is released
        Monitor.PulseAll(m_lock); // Wakes all waiters AFTER lock is released
        Monitor.Exit(m_lock); // Release lock
    }
}