We might have come across the deadlock detected error for a IIS hosted web application. When the issue happens it gets automatically fixed as IIS will recycle the w3wp process once the error happens. So the data collection over here has to be automated some or the other way. Below are some of the deadlock detected entries that we might see.
1) ISAPI 'C:\Windows\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll' reported itself as unhealthy for the following reason: 'Deadlock detected'.
2) ISAPI’C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll’ reported itself as unhealthy for the following reason: ‘Deadlock detected’”
3) Description: ISAPI 'C:\Windows\system32\inetsrv\asp.dll' reported itself as unhealthy for the following reason: 'ASP unhealthy because 100% of executing requests are hung and 0% of the request queue is full.'
In the below blog or link i have discussed as to why we see this error and what are the steps we need to follow to automate the data collection in case we see this issue to find out the root cause.
Hope this helps