"A CLR Profiler has already been attached" after few run with ForceGC

[bigbearzhu]

I used "HeapDump /ForceGC" directly to trigger GC on some process periodically. However I noticed that after it runs few times it start to throw errors like this: "A CLR Profiler has already been attached. You cannot attach another. (a process restart will fix)"

The problem is that I need keep the process running, e.g. w3wp process from iis. Is there anyway to find out why the profiler is still attached and how to detach it if possible?

[bigbearzhu]

Seems that the w3wp process is still having EtwClrProfiler.dll loaded after HeapDump quits.

[mjsabby]

@bigbearzhu you have to tear down the process, the dll once loaded in a certain way (i.e. from process startup) will always have it attached.

[bigbearzhu]

It is not attached at process startup. It is attached when HeapDump runs and detached after it finishes. It succeeds for a few times, and then start to fail to detach for some reason. Had a look at CorProfilerTracer.cpp line 298: if ((MatchAnyKeywords & DetachKeyword) != 0 && !m_profilerLoadedAtStartup && !m_detaching) Could m_profilerLoadedAtStartup be true when detaching so it is not detached?

https://msdn.microsoft.com/en-us/library/dd997942(v=vs.100).aspx#attach_details

Within the target process, the procedure for loading a profiler at attach-time is similar to the procedure for loading a profiler at startup-time: The CLR CoCreates the given CLSID, queries for the ICorProfilerCallback3 interface, and calls the ICorProfilerCallback3::InitializeForAttach method.

[bigbearzhu]

looked into the log of the EtwClrProfiler.dll. Seems it is getting error when trying to detach the profiler:

Creating new CorProfilerInstance
ClrProfiler Initializing
Registering the ETW provider
Initialize() returns 0
ProfilerControlCallback DoETWCommand IsEnabled 0x2 Level 0x5I64 MatchAny 0x0
DoETWCommand(IsEnabled=2, Level=5 Keywords=0x8000,0)
Detaching
Done Detaching Detaching ret = 0x80131363

while a successful detaching log is like this:

Creating new CorProfilerInstance
ClrProfiler Initializing
Registering the ETW provider
Initialize() returns 0
ProfilerControlCallback DoETWCommand IsEnabled 0x2 Level 0x5I64 MatchAny 0x0
DoETWCommand(IsEnabled=2, Level=5 Keywords=0x8000,0)
Detaching
Done Detaching Detaching ret = 0x0
ProfilerDetachSucceeded
Shutdown 
Destroying CorProfilerInstance

As far as I can find, 0x80131363 is CORPROF_E_UNSUPPORTED_CALL_SEQUENCE as from here which I totally have no clue how that could happen and be solved. :(

[MatteoPiovanelli-Laser]

I landed here because I have the same issue when attempting to force GC on w3wp

[msfcolombo]

I have same issue found on a different process (unrelated to w3wp). Mine is a very thread-hungry process, in case that rings some bells.