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Thread Validator Help

Navigation: Working with IIS and Services

Example Service Source Code

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Where to put your code


When you use the functions to load and unload Thread Validator from your service, it is important that you put the function calls in the correct place in your software.


The correct place to put them is in a 'balanced' location, such that you would expect no memory leaks to occur between the load and the unload function call, assuming the service was working correctly.


Typically, this means that Thread Validator is:


loaded as the first action in the service_main() function

unloaded just before the service control manager is informed of the stopped status

The source code shown below shows an example service_main() function used in a service, demonstrating where to load and unload Thread Validator.


The long comment covers problems with the way services are stopped and what may be displayed in a debugger if this happens.


seeAlsoThe code is extracted from service\service.cpp, part of the full example of an NT service, client and a utility for controlling whether the service uses Thread Validator.







void WINAPI service_main(DWORD dwArgc, LPTSTR *lpszArgv)


 // load Thread Validator here




         // register our service control handler:


 sshStatusHandle = RegisterServiceCtrlHandler(TEXT(SZSERVICENAME), service_ctrl);


 // SERVICE_STATUS members that don't change in example


 ssStatus.dwServiceType = SERVICE_WIN32_OWN_PROCESS;

 ssStatus.dwServiceSpecificExitCode = 0;


 // report the status to the service control manager.


 if (!ReportStatusToSCMgr(SERVICE_START_PENDING, NO_ERROR, 3000))


         if (sshStatusHandle)

                 ReportStatusToSCMgr(SERVICE_STOPPED, dwErr, 0);



 // do the work of the service


 doWork(dwArgc, lpszArgv);


 // unload Thread Validator here


 // Because of the way services work, you can find that this thread which is trying to gracefully unload

 // ThreadValidator is ripped from under you by the operating system. This prevents Thread Validator from

 // removing all its hooks successfully. If Thread Validator does not remove all of its hooks successfully

 // because this happens, then you may get a crash when the service stops.


 // A callstack for such a crash is shown below. If you see this type of crash you need to put your code to

 // unload Thread Validator somewhere else. The stack trace may be different, but a fundamental point is the

 // code calling through doexit(), exit() and ExitProcess()


 //NTDLL! 77f64e70()


 //MSVCRT! 78001436()

 //MSVCRT! 7800578c()

 //DBGHELP! 6d55da25()

 //DBGHELP! 6d55de83()

 //DBGHELP! 6d53705d()

 //DBGHELP! 6d51cc69()

 //DBGHELP! 6d51f6e8()

 //DBGHELP! 6d524ebf()

 //DBGHELP! 6d52a7b0()

 //DBGHELP! 6d52b00a()

 //DBGHELP! 6d526487()

 //DBGHELP! 6d5264d7()

 //DBGHELP! 6d5264f7()









 //MSVCRT! 78001436()

 //MSVCRT! 780057db()

 //KERNEL32! 77f19fdb()


 //doexit(int 0x00000000, int 0x00000000, int 0x00000000) line 392

 //exit(int 0x00000000) line 279 + 13 bytes

 //mainCRTStartup() line 345

 //KERNEL32! 77f1b9ea()




 // try to report the stopped status to the service control manager.


 if (sshStatusHandle)

         ReportStatusToSCMgr(SERVICE_STOPPED, dwErr, 0);


 // tried putting the call to svlTVStub_UnloadThreadValidator(); here but often the thread

 // was pulled from under it by the operating system