Performance Monitor Counters Cause Stop or Error Messages

• Microsoft Windows NT Workstation version 4.0
• Microsoft Windows NT Server version 4.0

SYMPTOMS

When you use Performance Monitor to monitor a computer (either locally or from a remote computer), the following blue screen STOP message may be produced on the computer being monitored:

STOP:0xC000021A (0xe1638608, 0xc0000005, 0x00000000, 0x00000000).

WinLogon.exe App. Error - The instruction at x77f648e2 referenced memory at x001cce35. The memory could not be read. Click OK to terminate the app.

CAUSE

When you use Performance Monitor to monitor a computer remotely, the initiating computer attaches to the target computer's Winlogon process through RPC. The Winlogon process has a perflib component in it for collecting data. The shared data is passed from the performance counters' .DLL to Winlogon on the target computer. The performance counters' DLLs sometimes overwrite their buffers. In the case of remote monitoring, this overwrite occurs in the context of the Winlogon process on the target computer, which causes it to have an access violation, compromises the Winlogon subsystem (which may create a breach of security), and forces Windows NT into kernel mode to start checking for bugs.

The performance counter DLLs make three functions available to other modules: Open, Collect, and Close. It is usually the Collect function that causes the problem.

RESOLUTION

Have the malfunctioning extensible Performance Counter fixed so that it does not overwrite its buffers.

-or-

Disable the malfunctioning performance counter's .dll by renaming or removing its entry from the Windows NT registry.

To locate all extensible performance counters, use Exctrlst.exe, which is part of the Windows NT 4.0 Resource Kit. You can run Exctrlst.exe locally or remotely to bring up a list of all of the extensible counters found in the computer's registry.

The counter's registry entries are located at the following key:


Hkey_Local_Machine\System\CurrentControlSet\Services\
Service_Name\Performance\Library.

NOTE: The above registry key is one path; it has been wrapped for readability.

To disable an extensible counter .dll:

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall Windows. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the Changing Keys and Values online Help topic in Registry Editor (Regedit.exe). Note that you should make a backup copy of the registry files (System.dat and User.dat) before you edit the registry.

1. Start Registry Editor using RegEdt32.exe.



2. At each performance entry listed by Exctrlst.exe, select the Library value and modify the library name by prefixing it with two x's. For example, if the library name is OrigLib.dll, change it to xxOrigLib.dll



3. When you have changed each performance entry under the CurrentControlSet\Services key, restart Perfmon to see if it works.



4. If Perfmon works, repeat steps 1 and 2, restoring the original library name, changing a new one, and trying Perfmon after each change to see which library causes the problem.
   
   - or -

1. If Exctrlst.exe is unavailable, start the Registry Editor using RegEdt32.exe.



2. Under the HKEY_LOCAL_MACHINE subtree, go to the following subkey:
   
   System\CurrentControlSet\Services



3. Click Find Key on the View menu.



4. Type "performance" as the search string, then search down from there.



5. To disable an extensible counter DLL when you find a performance entry, select the Library value and modify the library name by prefixing it with two x's: for example, if the library name is OrigLib.dll, change it to xxOrigLib.dll.



6. When you have changed each performance entry under the CurrentControlSet\Services key, restart Perfmon to see whether it works. If it does, then repeat steps 4 and 5, restoring each original library name and trying Perfmon after each change to see which library causes the problem.

1. Start Registry Editor (Regedt32.exe) and go to the following sub-key:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\
   \CurrentVersion\Perflib
   
   NOTE: The above registry key is one path; it has been wrapped for readability.
   
   Value: ExtCounterTestLevel
   Type: REG_DWORD
   Data: 2



2. Select the desired ExtCounterTestLevel value. You can choose a value ranging from 1 to 4:
   
   
   1. Most extensive testing, can be expensive.
   
   
   
   2. Basic testing.
   
   
   
   3. No testing.
   
   
   
   4. Don't even allocate a guard page (default from SP3 onwards).
   
   
   



3. Once this is entered, restart the system.

Additional query words: 0xc21A perfmon c000021a 0xc000021a

Keywords : kbtool ntstop NTSrvWkst prodnt
Version : WinNT:4.0
Platform : winnt
Issue type : kbprb