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copied!<p>This is pretty easy to solve with a timed latch. A latch is synchronization mechanism that is either opened or closed. When open threads are allowed to pass through. When closed threads cannot get through. A timed latch is one that will automatically reopen or reclose after a certain amount of time has elapsed. In this case we want a "normally opened" latch so the behavior is biased towards staying open. That means the latch will reopen automatically after the timeout, but close only if <code>Close</code> is explicitly called. Multiple calls to <code>Close</code> will reset the timer.</p> <pre><code>static NormallyOpenTimedLatch LatchThis = new NormallyOpenTimedLatch(t2); static NormallyOpenTimedLatch LatchThat = new NormallyOpenTimedLatch(t1); static void DoThis() { LatchThis.Wait(); // Wait for it open. DoThisStuff(); LatchThat.Close(); } static void DoThat() { LatchThat.Wait(); // Wait for it open. DoThatStuff(); LatchThis.Close(); } </code></pre> <p>And we can implement our timed latch like the following.</p> <pre><code>public class NormallyOpenTimedLatch { private TimeSpan m_Timeout; private bool m_Open = true; private object m_LockObject = new object(); private DateTime m_TimeOfLastClose = DateTime.MinValue; public NormallyOpenTimedLatch(TimeSpan timeout) { m_Timeout = timeout; } public void Wait() { lock (m_LockObject) { while (!m_Open) { Monitor.Wait(m_LockObject); } } } public void Open() { lock (m_LockObject) { m_Open = true; Monitor.PulseAll(m_LockObject); } } public void Close() { lock (m_LockObject) { m_TimeOfLastClose = DateTime.UtcNow; if (m_Open) { new Timer(OnTimerCallback, null, (long)m_Timeout.TotalMilliseconds, Timeout.Infinite); } m_Open = false; } } private void OnTimerCallback(object state) { lock (m_LockObject) { TimeSpan span = DateTime.UtcNow - m_TimeOfLastClose; if (span > m_Timeout) { Open(); } else { TimeSpan interval = m_Timeout - span; new Timer(OnTimerCallback, null, (long)interval.TotalMilliseconds, Timeout.Infinite); } } } } </code></pre>

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