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Jul 2

Written by: Shawn Bass
Thursday, July 02, 2009 10:35:17 AM 

So I've got a client that I've been rolling out HRP04 for XenApp 4.5 in order to resolve a nasty conflict between Microsoft App-V and Citrix's Client Drive provider cdm.sys that results in BSODs in certain circumstances when users of App-V applications try to perform I/O to their client drives.  The system BSODs with a Stop 8E.  I've been cautious about rolling out HRP04 because we've found re-introduction of some multimonitor glitches that were quite stable with HRP02 (as long as Post-HRP02 3040/3044 wasn't deployed - can't remember which of those two the seamless problem came from).  Anyway, I've got HRP04 rolled out to about 80% of the farm, but we have one app that was bombing in Seamless mode because the application didn't think that the session had an 800x600 sized display.  What's strange about this issue is that I ran a utility as a published app that clearly demonstrated that the session believed it had a multimonitor config with the correct screen resolutions.

In situations like this in the past, I've simply disabled Citrix's DLL hooking for whatever feature I had issues with.  I've done this successfully with the multimonitor hook in the past by following CTX110301  But in testing this particular app, I found it only solved the issue about 50% of the time.  The other 50% of the time it threw up the same minimum monitor resolution message and exited.  Well, I was in the process of opening a support case with Citrix (which was taking FOREVER BTW) when I stumbled across this gem in the above mentioned KB:

"The name should include the extension, is case-sensitive, and should be semicolon-delimited."

Sure enough switching the process name to it's proper case as displayed in Task Manager and the app was properly skipping the multimonitor hooking 100% of the time and is running without incident now.

My question is now this:  Is this truely a limitation of how the process hooking works?  Or is it merely a case-sensitive string comparison issue?  I'm hoping it's the former.

Secondly, we've learned that reading really IS important.  Your teachers were just giving you crap back in grade school

 

 

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1 comment(s) so far...

Re: MS App-V and Citrix CDM.SYS can BSOD Citrix servers and Citrix XenApp Multimonitor exception hooking is case sensitive, but why?

> My question is now this: Is this truely a limitation of how the process hooking works?
> Or is it merely a case-sensitive string comparison issue? I'm hoping it's the former.

That the failure exists 50% of the time says that the filename case changes 50% of the time and that doesn't make much sense. Put your "hooker hat" on, would you really want a module to "escape hooking" if the case on the file were changed? Answer: No, so you'd spend the extra cycles to do the case insensitive search. This means that the answer will be case insensitive despite claims and measurements. Sum that up and it isn't much help. Good luck Shawn.

By Joe Nord on   Thursday, July 02, 2009 2:55:11 PM

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