VB.NET并行与分布式编程(6)-线程与内核同步[16]

多线程与读写锁

最新推荐文章于 2025-06-01 12:14:40 发布

最新推荐文章于 2025-06-01 12:14:40 发布 · 121 阅读

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本文通过一个具体的示例程序介绍了如何使用.NET Framework中的ReaderWriterLockSlim来实现多线程环境下的读写操作。该程序创建了三个线程，分别进行读取和修改全局变量的操作，展示了读写锁的工作原理。

Imports System
Imports System.Threading
Imports System.Diagnostics
Imports System.Diagnostics.ThreadState











Module Module1
    Dim myLock As New ReaderWriterLockSlim()
    Dim jg As Double = 300
    Sub Main()

        Dim mythread1 As Thread
        Dim mythread2 As Thread
        Dim mythread3 As Thread





        '创建线程对象
        mythread1 = New Thread(AddressOf mythreadrun)
        mythread2 = New Thread(AddressOf mythreadrun)
        mythread3 = New Thread(AddressOf mythreadread)
        mythread1.Name = "thread_1"
        mythread2.Name = "thread_2"
        mythread3.Name = "thread_3"
        '设置线程优先级








        Console.WriteLine(Now.ToLongTimeString & "线程对象创建完毕,开始执行线程")
        Dim myprocess As Process = Process.GetCurrentProcess()
        Console.WriteLine("进程名称:" & myprocess.ProcessName)
        '执行线程
        mythread3.Start()
        mythread2.Start()
        mythread1.Start()





        '等待线程完成
        mythread1.Join()
        mythread2.Join()
        mythread3.Join()


        '线程执行完毕
        Console.WriteLine(Now.ToLongTimeString & "线程执行完毕!")

    End Sub
    Public Sub mythreadrun()
        Dim mynum As Double





        Try
            For mynum = 1 To 100
                '在3毫秒内获得写锁
                If myLock.TryEnterWriteLock(3) Then
                    jg -= mynum
                    Console.WriteLine(Thread.CurrentThread.Name & "获得写锁==>" & Now.ToLongTimeString & "=>" & (jg + mynum) & "-" & mynum & "，计算结果为：" & jg)
                    Thread.Sleep(3)
                    '退出写锁
                    myLock.ExitWriteLock()
                Else
                    Console.WriteLine(Thread.CurrentThread.Name & "==>" & Now.ToLongTimeString & "=>获得写锁失败")
                End If
                If jg < 0 Then
                    Exit For
                End If
                Thread.Sleep(8)
            Next
        Catch
            Console.WriteLine(Thread.CurrentThread.Name & "  " & Now.ToLongTimeString & "线程异常终止!")
            '终止线程
            Thread.CurrentThread.Abort()
        Finally
            Console.WriteLine(Thread.CurrentThread.Name & "优先级:  " & Thread.CurrentThread.Priority.ToString)
            Console.WriteLine(Thread.CurrentThread.Name & "  " & Now.ToLongTimeString & "线程运行完毕!")
        End Try
    End Sub
    Public Sub mythreadread()
        While jg > 0
            If myLock.TryEnterReadLock(2) Then
                Console.WriteLine(Thread.CurrentThread.Name & " 获得读锁，当前计算值为{0}", jg)
                Thread.Sleep(2)
                myLock.ExitReadLock()
            Else
                Console.WriteLine(Thread.CurrentThread.Name & " 获得读锁失败")
            End If
            Thread.Sleep(4)
        End While
    End Sub
End Module

ReaderWriterLockSlim.TryEnterReadLock 方法尝试进入读取模式锁定状态，可以选择整数超时时间。

如果调用线程已进入读取模式，则为 true；否则为 false。

效果如下: