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kIOFireWireOutOfTLabels
Asynchronous request correlation has run out
kIOFireWireOutOfTLabels reports exhaustion of FireWire transaction labels. Transaction labels are used to correlate outstanding asynchronous request/response activity; this is a request-concurrency limit, not an isochronous channel or bandwidth allocation error.
The likely cause is outstanding work that did not retire: a device response is delayed, a bus reset invalidated an operation path, cancellation failed to release state, or the caller submits work without bounded concurrency. The correct recovery begins by finding the oldest live transactions and their completion state.
Measure outstanding work
- Track each asynchronous request by transaction label, destination node, bus generation, tcode, submit time, and completion state.
- On reset, invalidate or reissue work only under the API's defined recovery rules; do not leave orphaned labels in application bookkeeping.
- Use a bounded per-node or per-controller request window and release capacity only on real completion or confirmed cancellation.
- Do not solve this by changing isochronous channel allocation; transaction labels belong to a different FireWire mechanism.
References
- Apple: IOFireWireFamilyCommon.h
- Apple: IOFireWireDeviceInterface
- Linux kernel: FireWire driver interface guide
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