What does macOS kernel return 41 (KERN_LOCK_OWNED_SELF) mean?

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: The calling thread already owns the Mach lock involved in the requested operation.

Could be also:
Constant	Type	OS
ippStsI18nMsgCatalogInvalid	Intel Ipp Status	Any
EWOULDBLOCK	errno	Linux
EPROTOTYPE	errno	Mac
ELNRNG	errno	Solaris
ENOTEMPTY	errno	Windows
SECURITY_SYSTEM	BugCheck Code	Windows

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KERN_LOCK_OWNED	KERN_SEMAPHORE_DESTROYED

KERN_LOCK_OWNED_SELF

Self-ownership exposes a reentrancy problem

KERN_LOCK_OWNED_SELF means the caller already owns the lock. This is different from contention with another thread: a simple wait cannot resolve it because the same thread must first unwind, release, or avoid the second incompatible lock operation.

The result identifies recursion or reentrancy in code that assumes a non-recursive lock contract, often through a callback, notification, error path, or helper that silently reaches the same guarded resource.

What to inspect

Capture the original acquisition stack and the second acquisition stack.
Check whether a callback executes before the first critical section has been exited.
Review cleanup and tracing code for hidden calls back into the guarded subsystem.
Do not replace a non-recursive lock with a recursive one unless the protected data invariants support reentrancy.

References

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