Correct way to register for pre-shutdown notification from C++

Question

I write a local service application using C++ and I can't find the correct way of registering for a pre-shut-down notification (for OS later than Windows XP). I believe that SERVICE_CONTROL_PRESHUTDOWN notification has been added since Vista, but when you call SetServiceStatus do we need to specify:

dwServiceStatus.dwControlsAccepted = SERVICE_ACCEPT_PRESHUTDOWN;

or

dwServiceStatus.dwControlsAccepted = SERVICE_ACCEPT_SHUTDOWN | SERVICE_ACCEPT_PRESHUTDOWN;

Answer 1

You cannot accept both a shutdown and a preshutdown if your service is correctly coded. The documentation explicitly states this.

From http://msdn.microsoft.com/en-us/library/windows/desktop/ms683241(v=vs.85).aspx:

Referring to SERVICE_CONTROL_PRESHUTDOWN:

A service that handles this notification blocks system shutdown until the service stops or the preshutdown time-out interval specified through SERVICE_PRESHUTDOWN_INFO expires.

In the same page, the section about SERVICE_CONTROL_SHUTDOWN adds:

Note that services that register for SERVICE_CONTROL_PRESHUTDOWN notifications cannot receive this notification because they have already stopped.

So, the correct way is to set the dwControlsAccepted to include either SERVICE_ACCEPT_SHUTDOWN or SERVICE_ACCEPT_PRESHUTDOWN, depending on your needs, but not to both at the same time.

But do note that you probably want to accept more controls. You should always allow at least SERVICE_CONTROL_INTERROGATE, and almost certainly allow SERVICE_CONTROL_STOP, since without the latter the service cannot be stopped (e.g. in order to uninstall the software) and the process will have to be forcibly terminated (i.e. killed).

Answer 2

As noted by the commenters above, you will need to choose from either SERVICE_ACCEPT_SHUTDOWN or SERVICE_ACCEPT_PRESHUTDOWN (Vista or later). If you are using SERVICE_ACCEPT_PRESHUTDOWN, you will need to register your service with the SCM using RegisterServiceCtrlHandlerEx instead of RegisterServiceCtrlHandler else you will not be receiving the pre-shutdown notifications. The handler prototype also changes from Handler to HandlerEx.

Another point to note is that handling pure shutdown events is limited to 5 seconds in Windows Server 2012 (and presumably Windows 8), 12 seconds in Windows 7 and Windows Server 2008, 20 seconds in Windows XP before your service is killed while stopping. This is the reason why you may need the pre-shutdown notification. You may want to change this at \\HKLM\SYSTEM\CurrentControlSet\Control\WaitToKillServiceTimeout.