• 29.4 内核模式构造


    29.4.1 Event构造

        class Program
        {
            static void Main()
            {
                int x = 0;
                const int iterations = 10000000;
                Stopwatch sw = Stopwatch.StartNew();
                
                // 1
                for (int i = 0; i < iterations; i++)
                {
                    x++;
                }
                Console.WriteLine("incrementing x:{0:N0}", sw.ElapsedMilliseconds);
    
                // 2
                sw.Restart();
                for (int i = 0; i < iterations; i++)
                {
                    M();
                    x++;
                    M();
                }
                Console.WriteLine("incrementing in M x:{0:N0}", sw.ElapsedMilliseconds);
    
                // 3
                SpinLock s1 = new SpinLock();
                sw.Restart();
                for (int i = 0; i < iterations; i++)
                {
                    bool taken = false;
                    s1.Enter(ref taken);
                    x++;
                    s1.Exit();
                }
                Console.WriteLine("incrementing in SpinLock x:{0:N0}", sw.ElapsedMilliseconds);
    
                // 4
                using (SimpleWaitLock sw1 = new SimpleWaitLock())
                {
                    sw.Restart();
                    for (int i = 0; i < iterations; i++)
                    {
                        sw1.Enter();
                        x++;
                        sw1.Leave();
                    }
                    Console.WriteLine("incrementing x in SimpleWaitLock:{0:N0}", sw.ElapsedMilliseconds);
                }
                //incrementing x:44
                //incrementing in M x:174
                //incrementing in SpinLock x:3,186
                //incrementing x in SimpleWaitLock: 33,481
    
                Console.ReadKey();
    
                //bool createdNew;      //此代码 仅供看
                //using (new Semaphore(0, 1, "SomeUniqueStringIdentifyingMyApp", out createdNew))
                //{
                //}
            }
            [MethodImpl(MethodImplOptions.NoInlining)]
            private static void M() { }
        }
        internal sealed class SimpleWaitLock : IDisposable
        {
            private readonly AutoResetEvent m_available;
            public SimpleWaitLock()
            {
                m_available = new AutoResetEvent(true); //最开始可自由使用
            }
            public void Enter()
            {
                //在内核中阻塞,直到资源可用
                m_available.WaitOne();
            }
            public void Leave()
            {
                //让另一个线程访问资源
                m_available.Set();
            }
            public void Dispose()
            {
                m_available.Dispose();
            }
        }

     29.4.3 Mutex构造

        /// <summary>
        /// 递归式AutoResetEvent优化版本
        /// </summary>
        internal sealed class RecursiveAutoResetEvent : IDisposable
        {
            private AutoResetEvent _lock = new AutoResetEvent(true);
            private int _owningThreadId = 0;
            private int _recursionCount = 0;
            public void Enter()
            {
                int currentThreadId = Thread.CurrentThread.ManagedThreadId;
                //如果调用线程拥有锁,就递增递归计数
                if (_owningThreadId == currentThreadId)
                {
                    _recursionCount++;
                    return;
                }
                //调用线程不拥有锁,等待它
                _lock.WaitOne();
                //调用的线程拥有了锁,初始化拥有锁的线程的ID和递归计数
                _owningThreadId = currentThreadId;
                _recursionCount = 1;
            }
            public void Leave()
            {
                //如果调线程不拥有锁,就出错了
                if (_owningThreadId != Thread.CurrentThread.ManagedThreadId)
                    throw new InvalidOperationException("调线程不拥有锁");
                //从递归数减1
                if (--_recursionCount==0)
                {
                    //如果递归计数 为0,表明没有线程拥有锁
                    _owningThreadId = 0;
                    _lock.Set();    //唤醒一个正在等待的线程(如果有的话)
                }
            }
            public void Dispose()
            {
                _lock.Dispose();
            }
        }
        /// <summary>
        /// Mutex互斥锁
        /// </summary>
        internal sealed class SomeClass : IDisposable
        {
            private readonly Mutex _lock = new Mutex();
            public void Method1()
            {
                _lock.WaitOne();
                //随便做什么事情
                Method2();      //Method2递归获取锁
                _lock.ReleaseMutex();
            }
            public void Method2()
            {
                _lock.WaitOne();
                //随便做什么事情
                _lock.ReleaseMutex();
            }
            public void Dispose()
            {
                _lock.Dispose();
            }
        }
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  • 原文地址:https://www.cnblogs.com/kikyoqiang/p/10225194.html
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