IIS errors since upgrading to dot net 4

Question

Back in October we upgraded one of our sites (on IIS 6) from .net 3.5 to .net 4.0. Since then we have been getting the following warning and error pretty much everyday:

Warning:

ISAPI 'c:\windows\microsoft.net\framework\v4.0.30319\aspnet_isapi.dll' reported itself as unhealthy for the following reason: 'Deadlock detected'.

Error:

It is not possible to run two different versions of ASP.NET in the same IIS process. Please use the IIS Administration Tool to reconfigure your server to run the application in a separate process.

We have checked all applications and ensured that they are running on the correct versions of ASP.NET and also in their own separate app pools.

We have looked at the IIS logs at the time the errors are recorded but this doesn't give any clues as to the issue. Is there a tool available that could give us more information as as to which application is causing the errors and what was happening at the time?

Answer 1

The discussion here might be helpfull for you as well:

You can configure the application pool to orphan the worker process rather than kill it when this condition happens - you can then use adplus to collect a hang dump of the worker process which can be analyzed to figure out what in the process is deadlocked.

(...)

It means that the asp.net thrads have not returned from whatever activity they were doing for a very long time and asp.net has run out of threads - this would normally indicate deadlock. This kb also talks about how to generate dumps for analysis for this condition.