c# - 如果另一个线程已获得关键部分的锁，如何停止线程？

Question

我创建了一个调度程序，它以 x 分钟的时间间隔执行一段程序。如果程序执行需要更多时间，则下一个作业不应等待当前作业完成。我正在使用 System.Timers.Timer。

_scheduler = new System.Timers.Timer(SomeMinutes);
_scheduler.Elapsed += new ElapsedEventHandler(OnTimedEvent);
_scheduler.Enabled = true;
_scheduler.AutoReset = true;

private void OnTimedEvent(object source, ElapsedEventArgs e)
{
   lock(obj)
   {
     //Critical Section
   }
}

如果我使用锁，下一个线程等待当前线程释放锁。我不想要这种行为。如果一个线程在临界区获得锁对象，那么另一个线程应该退出而不执行临界区

Answer 1

您可以使用Monitor。

MSDN:

The Monitor class controls access to objects by granting a lock for an object to a single thread. Object locks provide the ability to restrict access to a block of code, commonly called a critical section. While a thread owns the lock for an object, no other thread can acquire that lock. You can also use Monitor class to ensure that no other thread is allowed to access a section of application code being executed by the lock owner, unless the other thread is executing the code using a different locked object. More please...

但您可能会问，“这不是 c# 的 lock() 所做的吗？” 在某些方面是的。然而，Monitor 的真正好处是，您可以尝试获取锁并指定超时 等待，而不是阻塞线程直到时间可能结束或至少直到你读完那本 war 与和平。

此外，与 Mutex 不同，Monitor 使用起来很轻量级!就像 Windows 操作系统深层管道中的关键部分一样。

更改您的代码

private void OnTimedEvent(object source, ElapsedEventArgs e)
{
   lock(obj)
   {
     //Critical Section
   }
}

...到:

object _locker = new object();
const int SomeTimeout=1000;

private void OnTimedEvent(object source, ElapsedEventArgs e)
{
    if (!Monitor.TryEnter(_locker, SomeTimeout))
    {
        throw new TimeoutException("Oh darn");
    }

    try
    {
        // we have the lock so do something
    }
    finally
    {
        // must ensure to release the lock safely
        Monitor.Exit(_locker);
    }   
}

以下是 MSDN 对 TryEnter 的说明:

Attempts, for the specified number of milliseconds, to acquire an exclusive lock on the specified object - Tell me more...