Applications do not show a visible window (GUI), however, the process is loaded prematurely in the background and is visible in Task Manager
I have been recently looking at an issue for my client where users would report that some applications are not loading in their Citrix Published Desktop (Windows 2016 Server based).
- Windows 2016 Session Hosts
- Citrix XenApp 7.15
- Office 2013 Professional Plus
- ControlUp Agent 126.96.36.199 with Application Load Time feature enabled for Office Applications and some more apps.
I started with a quick “spot the difference” game, where I compare a working server to one with the issue. For this exercise, I took MS Word (winword.exe) as an example.
I noticed with some help from good old Process Explorer that the number of threads loaded in a healthy process is way more compared to the one with the issue; so I now moved my suspicion to what’s hooking the process and for that, I took a full process dump for analysis.
Using Windbg to analyze the dump, I could see that perfmod32.dll is reported as a failure module.
perfmod32.dll is a DLL file used by ControlUp to hook processes that are being monitored for load time.
Now that we know the failing module, I stopped ControlUp Agent Service and uninstalled the agent. Re-launched the application again and voilà! Apps started working again.
Upon contacting ControlUp Support (Which is really prompt and helpful) They advised that this is being reported more often recently and provided a private fix for my client.