【IT168 技术文档】前段时间仔细看过些关于多线程方面的资料，项目中用到线程的地方也不少，可是，当看了Jeffrey的一篇关于锁的文章后，发现自己虽然一直都在使用多线程，但是缺少了做多线程编程需要的思维！所以想从Jeffrey的Optex（锁）入手，来谈谈我从其中体会的东西。
在.NET中，我们用的最多的锁机制就是lock，用起来很简单，短短几行程序就可以实现，例如：
Lock 's Code
public class TestThreading
{
private System.Object lockThis = new System.Object();
public void Function()
{
lock (lockThis)
{
// Access thread-sensitive resources.
}
}
}
public class TestThreading
{
private System.Object lockThis = new System.Object();
public void Function()
{
lock (lockThis)
{
// Access thread-sensitive resources.
}
}
}
其实我们也明白，lock并不是锁，而是MS提供的一个简便式的写法，真正实现的是Monitor类中的Enter和Exit方法，既然提到了Monitor类也就说下有个需要注意的地方：
Pulse和PulseAll方法，这两个方法就是把锁状态将要改变的消息通知给等待队列中的线程，不过这时如果等待队列中没有线程，那么该方法就会一直等待下去，直到有等待的线程进入队列，也就是说该方法可能造成类试死锁的情况出现。
上面的lock + 线程(Thread和ThreadPool) = 多线程编程(N%)！？
对于该公式我曾经的N是80，现在是20。其中有很多东西影响我，让我从80->20，下面的Optex就是一个入口点。
Optex 's Code
public sealed class Optex : IDisposable {
private Int32 m_Waiters = 0;
private Semaphore m_WaiterLock = new Semaphore(0, Int32.MaxValue);
public Optex() { }
public void Dispose() {
if (m_WaiterLock != null)
{
m_WaiterLock.Close();
m_WaiterLock = null;
}
}
public void Enter() {
Thread.BeginCriticalRegion();
// Add ourself to the set of threads interested in the Optex
if (Interlocked.Increment(ref m_Waiters) == 1) {
// If we were the first thread to show interest, we got it.
return;
}
// Another thread has the Optex, we need to wait for it
m_WaiterLock.WaitOne();
// When WaitOne returns, this thread now has the Optex
}
public void Exit() {
// Subtract ourself from the set of threads interested in the Optex
if (Interlocked.Decrement(ref m_Waiters) > 0) {
// Other threads are waiting, wake 1 of them
m_WaiterLock.Release(1);
}
Thread.EndCriticalRegion();
}
}
public sealed class Optex : IDisposable {
private Int32 m_Waiters = 0;
private Semaphore m_WaiterLock = new Semaphore(0, Int32.MaxValue);
public Optex() { }
public void Dispose() {
if (m_WaiterLock != null)
{
m_WaiterLock.Close();
m_WaiterLock = null;
}
}
public void Enter() {
Thread.BeginCriticalRegion();
// Add ourself to the set of threads interested in the Optex
if (Interlocked.Increment(ref m_Waiters) == 1) {
// If we were the first thread to show interest, we got it.
return;
}
// Another thread has the Optex, we need to wait for it
m_WaiterLock.WaitOne();
// When WaitOne returns, this thread now has the Optex
}
public void Exit() {
// Subtract ourself from the set of threads interested in the Optex
if (Interlocked.Decrement(ref m_Waiters) > 0) {
// Other threads are waiting, wake 1 of them
m_WaiterLock.Release(1);
}
Thread.EndCriticalRegion();
}
}
