MemoryBarrier[通俗易懂]

         MemoryBarrier is required only on multiprocessor systems with weak memory ordering (for example, a system employing multiple Intel Itanium processors).

         Synchronizes memory access as follows: The processor executing the current thread cannot reorder instructions in such a way that memory accesses prior to the call to MemoryBarrier execute after memory accesses that follow the call to MemoryBarrier.

        就是说多核处理器会对运行CPU指令顺序重排优化，MemoryBarrier可以阻止指令重排，调用Thread.MemoryBarrier()之后的代码中内存访问不能再这之前就完成了。也就是它可以限制指令重排和内存读写的缓存。

     下面有段代码，在release编译情况下会死循环(debug应该是没做instructions reorder而不会有问题)

        bool complete = false;
        var t = new Thread(() =>
        {
            bool toggle = false;
            while (!complete)
                toggle = !toggle;
        });
        t.Start();
        Thread.Sleep(1000);
        complete = true;
        t.Join();

        bool complete = false;
        var t = new Thread(() =>
        {
            bool toggle = false;
            while (!complete)
            {
               Thread.MemoryBarrier();
                toggle = !toggle;
            }
        });
        t.Start();
        Thread.Sleep(1000);
        complete = true;
        t.Join();