What does macOS kernel return 0xE00002C4 (kIOReturnLockedWrite) mean?

kIOReturnLockedWrite

Do not retry a write blindly

kIOReturnLockedWrite reports that the device write path is locked. The common status does not say whether the lock is held by the same client, another client, a media transition, or a family-specific state machine. It says that the requested write cannot proceed in the current state.

This is important for recovery because writes can be state-changing. Unlike a read, a retry after a state change may duplicate a command or write data twice unless the interface defines idempotency or an operation identifier. Diagnose the locking transition and the request’s completion state before resubmission.

Useful checks

• Log the write range or command identity, caller, service state, and preceding open, claim, or configuration operations.
• Check whether a control operation, media transition, reset, or exclusive owner is expected to serialize writes.
• Wait for the documented completion or state notification instead of using a tight retry loop.
• Keep kIOReturnLockedWrite separate from a write capability failure such as kIOReturnNotWritable.

References

• Apple XNU source: IOReturn.h
• Apple: Introduction to IOKit Fundamentals
• Apple: Managing data in IOKit

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