What does NTSTATUS 0xC000071E (STATUS_CALLBACK_RETURNED_LDR_LOCK) mean?

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STATUS_CALLBACK_RETURNED_TRANSACTION	STATUS_CALLBACK_RETURNED_LANG

STATUS_CALLBACK_RETURNED_LDR_LOCK

The callback leaked the loader lock

The loader lock serializes sensitive DLL load, unload, and initialization activity. Returning a pooled worker while it still owns this lock can block future module operations and create lock-order deadlocks in unrelated callbacks. The status indicates a severe cleanup failure, not ordinary DLL search failure.

Avoid performing broad callback work from DllMain or other loader-locked paths. If callback code dynamically loads modules, do not call back into shutdown code that waits for pool work while holding loader-sensitive locks. Every acquisition must be balanced before the worker returns.

What to inspect

• Capture the worker stack, module operation, loader-lock owner, and any thread waiting for callback completion.
• Review DllMain for waits, thread synchronization, COM initialization, or pool teardown.
• Use documented load APIs without retaining private loader-lock state across callbacks.
• Check lock-order cycles between loader operations and cleanup-group waits.

References

• Microsoft Open Specifications: NTSTATUS values
• Microsoft: Dynamic-Link Library Best Practices
• Microsoft: SetThreadpoolCallbackLibrary
• Microsoft: pooled threads and callback environments

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