我有一个vb6多线程应用程序工作,我想使用互斥锁来保护数据。预期的行为是,当一个线程试图获得对现有互斥锁的锁定时,当调用“WaitForSingleObject”函数时,该线程将阻塞,直到发出互斥信号。我所遇到的是整个应用程序冻结。互斥锁使用多线程时冻结整个应用程序
要复制我的项目,请打开VB6并创建一个新的Active X EXE。使用默认名称创建一个模块。将此代码放置在它:
Option Explicit
Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Sub Main()
' this hack is necessary to ensure that we only 'create' the application window once..
Dim hwnd As Long
hwnd = FindWindow(vbNullString, "Form1")
If hwnd = 0 Then
Dim f As Form1
Set f = New Form1
f.Show
Set f = Nothing
End If
End Sub
接下来,创建一个类,使用默认名称和该代码添加到它:
Option Explicit
Private Const INFINITE = -1&
Private Const STANDARD_RIGHTS_REQUIRED As Long = &HF0000
Private Const SYNCHRONIZE As Long = &H100000
Private Const MUTANT_QUERY_STATE As Long = &H1
Private Const MUTANT_ALL_ACCESS As Long = (STANDARD_RIGHTS_REQUIRED Or SYNCHRONIZE Or MUTANT_QUERY_STATE)
Private Declare Function WaitForSingleObject Lib "kernel32" (ByVal hHandle As Long, ByVal dwMilliseconds As Long) As Long
Private Declare Function CreateMutex Lib "kernel32" Alias "CreateMutexA" (lpMutexAttributes As Any, ByVal bInitialOwner As Long, ByVal lpName As String) As Long
Private Declare Function OpenMutex Lib "kernel32" Alias "OpenMutexA" (ByVal dwDesiredAccess As Long, ByVal bInheritHandle As Long, ByVal lpName As String) As Long
Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
Private Declare Function ReleaseMutex Lib "kernel32" (ByVal hMutex As Long) As Long
Private Const MUTEX_NAME As String = "mymutex"
Private m_hCurrentMutex As Long
Public Sub Class_Terminate()
Call ReleaseIt
End Sub
Public Sub LockIt(success As String)
Dim hMutex As Long
MsgBox "Lockit t:" & App.ThreadID
hMutex = OpenMutex(STANDARD_RIGHTS_REQUIRED, 0, MUTEX_NAME)
If hMutex <> 0 Then
Form1.Caption = "waiting on mutex"
MsgBox "waiting t:" & App.ThreadID
Dim res As Long
Do
'MsgWaitForMultipleObjects
res = WaitForSingleObject(hMutex, INFINITE)
DoEvents
Loop While res = -1
m_hCurrentMutex = hMutex
Else
Form1.Caption = "creating mutex"
m_hCurrentMutex = CreateMutex(ByVal 0&, 1, MUTEX_NAME)
End If
Form1.Caption = success
MsgBox success
End Sub
Public Sub ReleaseIt()
If m_hCurrentMutex <> 0 Then
Call ReleaseMutex(m_hCurrentMutex)
Call CloseHandle(m_hCurrentMutex)
m_hCurrentMutex = 0
End If
End Sub
最后,在主窗体上添加4个命令按钮和下面的代码:
Option Explicit
Dim c(1) As Class1
'Lock
Private Sub Command1_Click()
If c(0) Is Nothing Then Set c(0) = CreateObject("Project1.Class1")
Call c(0).LockIt("Object0")
End Sub
Private Sub Command2_Click()
If c(1) Is Nothing Then Set c(1) = CreateObject("Project1.Class1")
Call c(1).LockIt("Object1")
End Sub
'Free
Private Sub Command3_Click()
If c(0) Is Nothing Then Set c(0) = CreateObject("Project1.Class1")
Call c(0).ReleaseIt
End Sub
Private Sub Command4_Click()
If c(1) Is Nothing Then Set c(1) = CreateObject("Project1.Class1")
Call c(1).ReleaseIt
End Sub
Private Sub Form_Unload(Cancel As Integer)
Set c(0) = Nothing
Set c(1) = Nothing
End
End Sub
前两个命令按钮锁定它们各自的互斥锁。第二两免费。注意在互斥锁被锁定之前,显示一个唯一的线程ID。这让我相信只有线程应该阻塞,而不是冻结整个应用程序。
任何援助将不胜感激。谢谢。
编辑:我忘了提及一个非常重要的部分:在项目属性部分,我已经设置为创建'每个对象的线程',这与msghox App.ThreadID调用的结果验证。
Ahh-我忘了提及一个非常重要的部分:在项目属性部分,我已经设置为创建'每个对象的线程',并且这通过msghox App.ThreadID调用的结果进行验证。关于使用相同的互斥体名称,这是必要的,因为我有各种变量需要保护。在这个演示应用程序中,没有任何内容实际上受到保护,但在应用程序中,我使用互斥体名称作为共享变量/内存的名称,以便即使我使用了互斥体,也不会冻结另一个线程的互斥体 - 因此只要它是一个不同的互斥体即可。 – 2011-12-19 20:19:44
@AuthmanApatira你能解释一下应用程序何时会阻塞(我没有安装VB6)。 – 2011-12-19 21:01:04
我会点击第一个锁按钮,并且会通知我线程ID,等待,然后我传入的字符串(object0)提醒我它已成功获取互斥锁。当我点击第二个锁按钮时,它会向我发送一个不同的,唯一的线程ID,等待---然后游戏结束。如果我将dowhile循环注释掉,并且只留下waitforsingleobject行,它将返回-1(失败)并立即继续处理该函数。所以这些事件实际上并没有帮助/做任何事情。我在想,因为它的一个新的线程,也许它需要处理窗口消息,因此msgwait线,但iono – 2011-12-19 22:53:43