macOS kernel return 36 (KERN_NOT_DEPRESSED): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: thread_depress_abort was called when the target thread had no active scheduling depression.

Could be also:
Constant	Type	OS
ERROR_SHARING_BUFFER_EXCEEDED	Win32 error	Windows
ippStsNotSupportedCpu	Intel Ipp Status	Any
ENAMETOOLONG	errno	Linux
EINPROGRESS	errno	Mac
EIDRM	errno	Solaris
EDEADLK	errno	Windows
NTFS_FILE_SYSTEM	BugCheck Code	Windows

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KERN_INVALID_SECURITY	KERN_TERMINATED

KERN_NOT_DEPRESSED

No active scheduling depression to cancel

KERN_NOT_DEPRESSED is tied to the historical Mach scheduling-depression mechanism. thread_depress_abort cancels a depression caused by thread_switch; this result means that no such active depression was present for the target thread when the abort was attempted.

The condition can be a normal timing outcome: the depression may already have expired, the thread may have run, or another path may have cleared it. It is not evidence that the target thread is blocked, terminated, or permanently low priority.

What to inspect

Log the original thread_switch option and requested duration together with the later abort attempt.
Capture the target thread lifecycle and scheduler state at both points.
Use an idempotent cleanup policy when the caller only needs to ensure that no depression remains.
Do not reinterpret this code as a user-space thread-priority failure.

References

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