System Crash (STOP error) 0x7F, Unexpected Kernel Mode Trap (Identifying Kernel Stack Overflow Crashes)

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Summary

This Knowledgebase article provides information about System Crash (STOP error) 0x7F, Unexpected Kernel Mode Trap. (Identifying Kernel Stack Overflow Crashes).


More Information

Stop Code (or Bugcheck) 0x7F (UNEXPECTED_KERNEL_MODE_TRAP) with a first parameter of 0x8 is known as a double fault.

There are two common causes of a double fault:

  • A hardware problem.
  • A kernel stack overflow.

A kernel stack overflow can occur when there are too many File System Filter Drivers (FSFDs) attempting to make use of a thread’s stack.

Neverfail Heartbeat includes a component that is a File System Filter Driver – nfdrv.sys. If a crash with this footprint is experienced on the active server when running Heartbeat, there is good chance that the root cause is a kernel stack overflow.

A kernel stack overflow is simply a result of having too many FSFDs running on the shared and limited stack resource provided by Windows.

To determine if this is the cause, the machine should be inspected for other software that makes use of such technology. These may include:

  • File level Anti-Virus software (e.g. Symantec Anti-Virus).
  • Backup Utilities (e.g. Veritas Storage Replicator).
  • Hierarchical Storage utilities.
  • Special purpose file encryption or compression utilities.

If other products with FSFD technology are installed, the end-user may have to make a priority decision and remove some of these until enough stack resource is available to those remaining. This may require a number of system configuration permutations before the crash disappears.

To conclusively determine that a kernel stack overflow is the cause of the crash and see exactly what drivers have contributed to the overflow, the memory dump must be delivered to Neverfail Support for analysis. See Knowledgebase article #146 - 'How to Retrieve the Neverfail Heartbeat Logs and Other Useful Information for Support Purposes' and Knowledgebase article #148 - 'System Crash (STOP error), General Advice for Support Partners, Including Steps Towards Initial Diagnosis' for information about collating and providing this information.

See Knowledgebase article #147 - 'System Crash (STOP error), General Advice for end-users' and Knowledgebase article #148 - 'System Crash (STOP error), General Advice for Support Partners, Including Steps Towards Initial Diagnosis' for general information relating to STOP errors.


Applies To

All Versions


Related Information

None

KBID-149

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