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kOSKextReturnInUse
Unload is blocked by active use or references
kOSKextReturnInUse means that the kext is currently in use or has outstanding references and cannot be unloaded. XNU’s OSKext API documentation explains that autounload requires no outstanding references and no live instances of the kext’s Libkern C++ subclasses.
This is a lifecycle status, not a policy or integrity failure. The correct evidence is the ownership chain that retains the kext, not a repeated force-unload attempt that might obscure the client or service still using it.
What to inspect
- Outstanding references, active service instances, mounts, devices, or other clients depending on the kext.
- Whether the kext has autounload enabled and which condition keeps its last reference from being released.
- Whether the operation is an explicit unload or a stop transition with concurrent users.
Do not confuse this status with kOSKextReturnStopping: that code says the stop process is already in progress and further requests cannot be made.
References
- Apple XNU: OSKextLib.h, reference and autounload behavior
- Apple Platform Security: modern alternatives to in-kernel extensions
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