How can I reject a Windows "Service Stop" request in ATL 7? - com

Question

I have a Windows service built upon ATL 7's CAtlServiceModuleT class. This service serves up COM objects that are used by various applications on the system, and these other applications naturally start getting errors if the service is stopped while they are still running.
I know that ATL DLLs solve this problem by returning S_OK in DllCanUnloadNow() if CComModule's GetLockCount() returns 0. That is, it checks to make sure no one is currently using any COM objects served up by the DLL. I want equivalent functionality in the service.
Here is what I've done in my override of CAtlServiceModuleT::OnStop():
void CMyServiceModule::OnStop()
{
if( GetLockCount() != 0 ) {
return;
}
BaseClass::OnStop();
}
Now, when the user attempts to Stop the service from the Services panel, they are presented with an error message:
Windows could not stop the XYZ service on Local Computer.
The service did not return an error. This could be an internal Windows error or an internal service error.
If the problem persists, contact your system administrator.
The Stop request is indeed refused, but it appears to put the service in a bad state. A second Stop request results in this error message:
Windows could not stop the XYZ service on Local Computer.
Error 1061: The service cannot accept control messages at this time.
Interestingly, the service does actually stop this time (although I'd rather it not, since there are still outstanding COM references).
I have two questions:
Is it considered bad practice for a service to refuse to stop when asked?
Is there a polite way to signify that the Stop request is being refused; one that doesn't put the Service into a bad state?

Answer 1

You can't do this. Once the SCM sends a SERVICE_CONTROL_STOP to your service, you have to stop.
If your other apps are also services, you can make them dependencies within the SCM. Of course, if the apps using this service are just regular applications that can't be used.

Answer 2

When ATL's lock count increments to 1, call SetServiceStatus() with the SERVICE_ACCEPT_STOP flag omitted in the SERVICE_STATUS::dwControlsAccepted field. Then you will not receive any SERVICE_CONTROL_STOP requests at all. Any attempt to stop the service will fail immediately. When ATL's lock count falls back to 0, call SetServiceStatus() again with the SERVICE_ACCEPT_STOP flag specified.
I just had to do this in 2 (older) ATL-based services, and it works well. Granted, I was unable to figure out the best way to override Lock() and Unlock() directly, so I just put a small loop inside my service that checks GetLockCount() at frequent intervals and calls SetServiceStatus() when needed.

Answer 3

In your constructor, update m_status.dwControlsAccepted removing SERVICE_ACCEPT_STOP. For instance:
CMyServiceModule::CMyServiceModule()
: ATL::CAtlServiceModuleT<CMyServiceModule, IDS_SERVICENAME>()
{
m_status.dw &= ~SERVICE_ACCEPT_STOP
}