macOS kernel return 48 (KERN_NOT_WAITING): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: A signal targeted a thread that was not waiting at that time.

Could be also:
Constant	Type	OS
ippStsSizeWrn	Intel Ipp Status	Any
ELNRNG	errno	Linux
EADDRINUSE	errno	Mac
ENOTSUP	errno	Solaris
SET_OF_INVALID_CONTEXT	BugCheck Code	Windows

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KERN_NODE_DOWN	KERN_OPERATION_TIMED_OUT

KERN_NOT_WAITING

A signal found no active wait

KERN_NOT_WAITING means the signaling operation found that the target thread was not actually waiting. It is not a timeout and does not state that the intended event is invalid; it records a mismatch between the signal attempt and the thread current wait state.

In event-driven code, this often points to a race between waking, cancellation, timeout, or state reuse. The diagnosis needs the ordering of those transitions, not a larger timeout or a blind repeat of the signal.

What to inspect

Record the event, target thread, and exact time of the signal attempt.
Capture prior wakeups, timeouts, cancellation, and destruction events for the same wait.
Check that each signal is associated with a documented wait condition rather than a stale thread reference.
Compare with KERN_ALREADY_WAITING, which indicates the opposite invalid transition: entering the same wait twice.

References

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