KB2984972 May Cause Problems with 32-bit App-V 4.6 Applications Using splwow64.exe to Print on 64-bit Windows 7 Print E-mail
Windows 64-bit
Written by Darwin Sanoy   
Wednesday, October 29, 2014 6:24pm
On 64-Bit Windows splwow64.exe is automatically used to interface 32-bit applications with 64-bit print drivers as part of the overall WOW64 subsystem.  Recently we applied KB2984972 and printing stopped working on most 32-bit App-V packages.

Once splwow64.exe is started - all 32-bit applications will use the same instance to print - until it timeouts and unloads itself.  So once an App-V 4.6 packaged application starts splwow64.exe it affects all 32-bit software that attempts to print - whether or not it is an App-V packaged application.  

Also, if the in memory instance of splwow64.exe is was started by a non-virtualized application - it prints fine for both virtualized and non-virtualized apps.

From a procexp.exe stack trace (with symbols configured), it appears that splwow64 starts to spin while waiting for an API "WaitforLsmStart" in winsta.dll.  LSM -= local security manager.  Since KB2984972 was the only one of six recent security updates we applied that played with LSA (Local Security Authority) files - it was isolated for testing with it uninstalled.

These are the kinds of skills we help you get started with in Windows Application Packaging, Provisioning and Troubleshooting Engineer Bootcamp (ENG-55) which was recently held in Utrecht, Netherlands.