Deep understanding Net (2) kernel mode 4 Summary of kernel pattern constructs

In depth understanding of .Net The construction mode of thread synchronization in （ Two ） Kernel mode construction

Preface

Kernel-mode Constructs Generally translated as kernel mode construction ,
Constructs It is both a noun and a verb , But the translation for construction feels a bit like a verb , I think it's better to translate it into a noun , After all s Of , It means multiple , Verbs obviously can't express more than one , Such as kernel mode constructs , Kernel mode constructs .

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Environmental statement
IDE：Visual Studio 2022
OS：Win10
.NET：.Net4.6.1

One 、 The advantages of kernel mode

Ahead of us 3 The first section briefly introduces three common constructs of a kernel construct , Now let's talk about why we use kernel constructs ？ Advantages of kernel constructs ？
An important advantage of kernel mode is that it can synchronize threads across processes （ We restrict our application to only one program ）
Compared to the user mode spin , Kernel mode constructs block threads
You can synchronize between managed threads and local threads
Can be based on EventWaitHandleSecurity Perform certain thread access control

Two 、 Code writing

1. be based on EventWaitHandle Transform a simple lock

The code is as follows （ Example ）：

  public sealed class EventLock : IDisposable
    {
    
        private readonly EventWaitHandle m_available;
        public EventLock()
        {
    
            m_available = new EventWaitHandle(true,EventResetMode.AutoReset,"testEvent"); // Initially free
        }

        public void Enter()
        {
    
            Int32 currentThreadId = Thread.CurrentThread.ManagedThreadId;
            Console.WriteLine($" Threads ID：{
      currentThreadId},{
      DateTime.Now}, Blocking wait start ");
            // Block in kernel until resource available
            m_available.WaitOne();
            Console.WriteLine($" Threads ID：{
      currentThreadId},{
      DateTime.Now}, Blocking waiting for completion ");
        }

        public void Leave()
        {
    
            // Let another thread access the resource
            m_available.Set();
        }

        public void Dispose() 
        {
    
            m_available.Dispose(); 
        }
    }

2. test InterProcessLockTest The effect of cross thread locking

The code is as follows （ Example ）：

    internal class Program
    {
    
        static void Main(string[] args)
        {
    
            new InterProcessLockTest().TestStart();
            Console.ReadLine();
        }
    }
    
   public class InterProcessLockTest
    {
    
        public void TestStart()
        {
    

            Console.WriteLine(" InterProcessLockTest TestStart Start !");
            IntObj intObj = new IntObj();
            EventLock eventLock = new EventLock();
            eventLock.Enter();
            Console.WriteLine($"get lock,{
       DateTime.Now}");
            Thread.Sleep(1000*30);
            Console.WriteLine($"wait 30s,{
       DateTime.Now}");
            Console.WriteLine(" InterProcessLockTest TestStart END !");
        }
    }

Let's finish the editing first , Get into debug Run the console program directly under the directory , You can see the following

And then it starts visual studio Debugging interface

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We can analyze the code to know , After acquiring a lock , We will not release the lock , At this time, we restart a program （ Can be seen as a process ）, At this time , The process could not acquire the lock , Because there is no lock release in another process .
This is cross process synchronization