为什么第三个线程不执行？ ( 积分: 30 )

awfigsk · 2005-11-16

unit threadUnit; interface uses  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,  StdCtrls, Gauges; type  TForm1 = class(TForm)    CreateThread: TButton;    procedure CreateThreadClick(Sender: TObject);  private    ThreadHandle : THandle;    ThreadHandle1 : THandle;    ThreadHandle2 : THandle;    MutexHandle: THandle;    { Private declarations }  public    { Public declarations }  end; var  Form1: TForm1; implementation {$R *.DFM} function ThreadFunc0(Info: Pointer): Integer; stdcall var  ICount: Integer;        // general loop counter  CountStr: string;       // holds a string representation of the counter begin  WaitForSingleObject(Form1.MutexHandle, INFINITE);  for ICount := 1 to 10000 do  begin    CountStr := IntToStr(ICount);    Form1.Canvas.TextOut(10, 10, 'Thread 1 '+CountStr);  end;  ReleaseMutex(Form1.MutexHandle);  ExitThread(1); end; function ThreadFunc1(Info: Pointer): Integer; stdcall var  ICount: Integer;        // general loop counter  CountStr: string;       // holds a string representation of the counter begin  WaitForSingleObject(Form1.MutexHandle, INFINITE);  for ICount := 1 to 10000 do  begin    CountStr := IntToStr(ICount);    Form1.Canvas.TextOut(110, 10, 'Thread 2 '+CountStr);  end;  ReleaseMutex(Form1.MutexHandle);  ExitThread(2); end; function ThreadFunc2(Info: Pointer): Integer; stdcall var  ICount: Integer;           // general loop counter  CountStr: string;          // holds a string representation of the counter  LocalMutexHandle: THandle; // holds a handle to the mutex begin  LocalMutexHandle := OpenMutex(MUTEX_ALL_ACCESS, FALSE, 'MyMutex');  WaitForSingleObject(LocalMutexHandle, INFINITE);  for ICount := 1 to 10000 do  begin    CountStr := IntToStr(ICount);    Form1.canvas.TextOut(210, 10, 'Thread 3 '+CountStr);  end;  ReleaseMutex(LocalMutexHandle);  CloseHandle(LocalMutexHandle);  ExitThread(3); end; procedure TForm1.CreateThreadClick(Sender: TObject); var  ThreadId0, ThreadId1, ThreadId2: DWORD; // holds thread identifiers begin  MutexHandle := CreateMutex(nil, False,'MyMutex');  ThreadHandle := Windows.CreateThread(nil, 0, @ThreadFunc0, nil, 0, ThreadId0);  ThreadHandle1 := Windows.CreateThread(nil,0, @ThreadFunc1, nil, 0, ThreadId1);  ThreadHandle2 := Windows.CreateThread(nil,0, @ThreadFunc2, nil, 0, ThreadId2);  Sleep(1000);  WaitForSingleObject(MutexHandle, INFINITE);  CloseHandle(MutexHandle); end; 上面这段代码执行后，线程3好像不会执行，但是我如果将线程３的建立语句ThreadHandle2=....放到ThreadHandle或Threadhandle1前面，则处理第三个位置的Thread建立语句好像都不会执行，并且我将Sleep的值设大也不会执行。 但当我在ThreadFunc2中最前面加入一个showmessage()语句来进行调试时，Thread3又可以执行，去掉这条语句就不会执行。这个问题是出在哪？ 还请高手大侠们指点，谢谢！

awfigsk · 2005-11-16

unit threadUnit; interface uses  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,  StdCtrls, Gauges; type  TForm1 = class(TForm)    CreateThread: TButton;    procedure CreateThreadClick(Sender: TObject);  private    ThreadHandle : THandle;    ThreadHandle1 : THandle;    ThreadHandle2 : THandle;    MutexHandle: THandle;    { Private declarations }  public    { Public declarations }  end; var  Form1: TForm1; implementation {$R *.DFM} function ThreadFunc0(Info: Pointer): Integer; stdcall var  ICount: Integer;        // general loop counter  CountStr: string;       // holds a string representation of the counter begin  WaitForSingleObject(Form1.MutexHandle, INFINITE);  for ICount := 1 to 10000 do  begin    CountStr := IntToStr(ICount);    Form1.Canvas.TextOut(10, 10, 'Thread 1 '+CountStr);  end;  ReleaseMutex(Form1.MutexHandle);  ExitThread(1); end; function ThreadFunc1(Info: Pointer): Integer; stdcall var  ICount: Integer;        // general loop counter  CountStr: string;       // holds a string representation of the counter begin  WaitForSingleObject(Form1.MutexHandle, INFINITE);  for ICount := 1 to 10000 do  begin    CountStr := IntToStr(ICount);    Form1.Canvas.TextOut(110, 10, 'Thread 2 '+CountStr);  end;  ReleaseMutex(Form1.MutexHandle);  ExitThread(2); end; function ThreadFunc2(Info: Pointer): Integer; stdcall var  ICount: Integer;           // general loop counter  CountStr: string;          // holds a string representation of the counter  LocalMutexHandle: THandle; // holds a handle to the mutex begin  LocalMutexHandle := OpenMutex(MUTEX_ALL_ACCESS, FALSE, 'MyMutex');  WaitForSingleObject(LocalMutexHandle, INFINITE);  for ICount := 1 to 10000 do  begin    CountStr := IntToStr(ICount);    Form1.canvas.TextOut(210, 10, 'Thread 3 '+CountStr);  end;  ReleaseMutex(LocalMutexHandle);  CloseHandle(LocalMutexHandle);  ExitThread(3); end; procedure TForm1.CreateThreadClick(Sender: TObject); var  ThreadId0, ThreadId1, ThreadId2: DWORD; // holds thread identifiers begin  MutexHandle := CreateMutex(nil, False,'MyMutex');  ThreadHandle := Windows.CreateThread(nil, 0, @ThreadFunc0, nil, 0, ThreadId0);  ThreadHandle1 := Windows.CreateThread(nil,0, @ThreadFunc1, nil, 0, ThreadId1);  ThreadHandle2 := Windows.CreateThread(nil,0, @ThreadFunc2, nil, 0, ThreadId2);  Sleep(1000);  WaitForSingleObject(MutexHandle, INFINITE);  CloseHandle(MutexHandle); end; 上面这段代码执行后，线程3好像不会执行，但是我如果将线程３的建立语句ThreadHandle2=....放到ThreadHandle或Threadhandle1前面，则处理第三个位置的Thread建立语句好像都不会执行，并且我将Sleep的值设大也不会执行。 但当我在ThreadFunc2中最前面加入一个showmessage()语句来进行调试时，Thread3又可以执行，去掉这条语句就不会执行。这个问题是出在哪？ 还请高手大侠们指点，谢谢！

bbscom · 2005-11-16

单独建立一个线程单位，然后引用公共的执行事件就可以了。

awfigsk · 2005-11-16

主要是为什么第三个线程执行不了？ 我将CreateThread按钮的Click事件改成如下，并且将线程中循环的值加大，设为１０００００，这时有时可以三个线程的TextOut都显示出来，但有时只能显示第一和第三个线程，第二个线程反而不执行,并且有时第三个线程的值不会到达１０００００，而是小于１０００００的值,就不执行了。 在下面的第一个Textout有时会将'主线程'显示出来，很少可以三个Textout都显示出来，有时一个TextOut都不会显示出来。 procedure TForm1.CreateThreadClick(Sender: TObject); var  ThreadId0, ThreadId1, ThreadId2: DWORD; // holds thread identifiers begin  MutexHandle := CreateMutex(nil, False,'MyMutex');  ThreadHandle := Windows.CreateThread(nil, 0, @ThreadFunc0, nil, 0, ThreadId0);  ThreadHandle1 := Windows.CreateThread(nil,0, @ThreadFunc1, nil, 0, ThreadId1);  ThreadHandle2 := Windows.CreateThread(nil,0, @ThreadFunc2, nil, 0, ThreadId2);  Sleep(5000);  Form1.Canvas.TextOut(10,30,'主线程');  Form1.Canvas.TextOut(10,60,'主线程WaitForSingleObject');  CloseHandle(MutexHandle);  Form1.Canvas.TextOut(10,80,'主线程CloseHandle'); end; 上面这个程序的执行原理是怎么样的呢？很是糊涂！

Lucker · 2005-11-22

是因为建立第三个线程的语句的下面代码不管是 Sleep(1000) 还是 WaitForSingleObject(MutexHandle, INFINITE); 都会使主线程阻塞，也就是说这时它不会处理任何消息，包括刷新界面，但你的第三个 个线程此时又正在更新界面，由于主线程已经被阻塞，所以线程三会在等待，主线程也会 在等待，这就是线程三看起来不会被执行的原因。 ------------------------------------------------------------------------------ 自由界面和报表的完美解决方案 http://www.anylib.com

Lucker · 2005-11-22

不管是哪个子线程，只要主线程进入阻塞，那么子线程(可能正在执行到半或还没执行)都会被挂起，这也能解释你把循环加大出现的状况。

wqyzsh · 2005-11-22

Sleep(1000); WaitForSingleObject(MutexHandle, INFINITE); CloseHandle(MutexHandle); 去掉就可以了,

为什么第三个线程不执行？ ( 积分: 30 )

awfigsk

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awfigsk

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bbscom

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awfigsk

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Lucker

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Lucker

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wqyzsh

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