How to wait on a system process from a user process?

Question

I have a .net Windows Service running as Local System. I have another .net process that needs to wait for the service to terminate. That process does not know the service name so it can't query the service control manager. It does know the service process Id. I can modify sources of both the windows service and the other process.

When I do:

process = Process.GetProcessById(processId);
process.WaitForExit();

from the other process, I'm getting:

System.ComponentModel.Win32Exception: Access is denied

Stack trace: 
  at System.Diagnostics.Process.GetProcessHandle(Int32 access, Boolean throwIfExited)
  at System.Diagnostics.Process.WaitForExit(Int32 milliseconds)

GetProcessHandle calls OpenProcess. Apparently the target process should allow SYNCHRONIZE bit for the above to work, which in theory can be set by SetSecurityInfo from the Windows Service. However it does not appear that there is an easy way of doing this in .NET short of calling several pinvokes to elevate, enable privilege and finally change the security.

Am I overlooking a simple way of waiting on another (system) process from a user process?

Is your process 32 bit and service is 64 bit? IIRC there are some restriction in what 32 bit process can query about 64 bit process. — Sriram Sakthivel, Oct 15 '14 at 09:49
Which line throws `Win32Exception`. It is `GetProcessById` or `WaitForExit`? — Sriram Sakthivel, Oct 15 '14 at 09:52
WaitForExit. Inside .net it calls GetProcessHandle and passes it the SYNCHRONIZE access mask. This results in the "Access Denied" we are seeing. — Andrew Savinykh, Oct 15 '14 at 09:53
Another thing you could try subscribing to Process.Exited event.. http://msdn.microsoft.com/en-us/library/system.diagnostics.process.exited.aspx — Vinoth, Oct 15 '14 at 09:54
@Vinoth I was sure that would not work either but I just tried and what do you know, it worked... Thank you. — Andrew Savinykh, Oct 15 '14 at 09:59
@zespri Are you sure that worked? Am skeptical. I get access denied when setting `EnableRaisingEvents` to true. Without that `Exited` event wont be raised — Sriram Sakthivel, Oct 15 '14 at 10:03
@SriramSakthivel Yep, I take that back, it did not. Spoke too soon. — Andrew Savinykh, Oct 15 '14 at 10:06
http://stackoverflow.com/questions/11637764/how-do-i-set-acl-for-a-windows-service-in-net — Hans Passant, Oct 15 '14 at 13:07
There's another theoretical issue with this approach: the service manager does not guarantee that the process will exit when the service stops. (Although AFAIK it always does in practice, unless multiple services share the same process.) — Harry Johnston, Oct 16 '14 at 21:14

Harley · Answer 1 · 2014-10-15T11:19:21.033

Try use the same user account to start the service and your program, Or use the built in Administrator account to run your program(Windows Vista and after).

If it still throw the exception, try set your computer's DEP(Data Execution Prevention) setting.

Updated: Maybe you could use this stupid code.. It's trouble for getting the Service Name, since it may not the same as Process.Name.

static ServiceController GetServiceControllerByPId(int processId)
{

    string serviceName = "";

    string qry = "SELECT NAME FROM WIN32_SERVICE WHERE PROCESSID = " + processId.ToString();
    System.Management.ManagementObjectSearcher searcher = new System.Management.ManagementObjectSearcher(qry);
    System.Management.ManagementObjectCollection mngntObjs = searcher.Get();

    foreach (System.Management.ManagementObject mngntObj in mngntObjs)
    {
        serviceName = (string)mngntObj["NAME"];
    }
    if (serviceName == "")
    {
        return null;
    }

    return System.ServiceProcess.ServiceController.GetServices().FirstOrDefault(x => x.ServiceName == serviceName);
}

Call this function, and monitor the ServiceController.Status

This unfortunately is not an option. The service needs to run as local system and the process needs to run under current user account. But thank you for the suggestion. — Andrew Savinykh, Oct 15 '14 at 10:07

score 0 · Answer 2 · answered Oct 15 '14 at 10:32

0

If you know the service process ID, Why can't you get the service name and check for the service status from process as follows ?

Process process = Process.GetProcessById(1);
ServiceController windowsService = ServiceController.GetServices().FirstOrDefault(x => x.ServiceName == process.ProcessName);

//Wait until the windows service stops running
while (windowsService.Status == ServiceControllerStatus.Running)
{
   Thread.Sleep(1000);
}

answered Oct 15 '14 at 10:32

Kurubaran

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The service name maybe not the same as process name. – Harley Oct 15 '14 at 11:25
Perhaps you could P/Invoke QueryServiceStatusEx to get the process ID for each service? – Harry Johnston Oct 16 '14 at 21:23

How to wait on a system process from a user process?

2 Answers2