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STATUS_RING_PREVIOUSLY_ABOVE_QUOTA
Quota crossing is a flow-control event, not a packet-format failure
STATUS_RING_PREVIOUSLY_ABOVE_QUOTA describes a ring whose outstanding-transaction level has fallen below a quota after progress was made. The word quota is significant: this is a threshold crossing in accounting or flow control, not the same condition as the physical ring becoming non-full.
Packet-ring transports often track more than bytes available. Microsoft VMBus KMCL documents packet objects whose lifetime can extend until a completion packet returns from the opposite endpoint, and synchronous request support explicitly waits for a response. That makes outstanding transactions a distinct resource from raw ring capacity. The NTSTATUS definition itself does not identify a particular transport, so the returning subsystem must be recorded before assigning protocol-specific meaning.
For diagnosis, log the quota value, outstanding count before and after completion, transaction or request identifier, and whether the completion retires all associated resources. A leak in completion accounting can hold the count above quota even when the ring has free bytes. The inverse bug is decrementing twice, which can prematurely reopen submission. Treat the status as a cue to examine the admission-control path that was waiting for the count to fall.
What to inspect
- Capture quota and outstanding-transaction counters atomically with the operation.
- Correlate decrements with transaction IDs or packet completion callbacks.
- Separate byte-capacity pressure from completion/quota pressure in metrics.
References
- Microsoft Open Specifications: NTSTATUS values
- Microsoft WDK: VmbPacketSend
- Microsoft WDK: VmbChannelSendSynchronousRequest
- Microsoft WDK: VMBus KMCL API
- Linux kernel: VMBus channels and transaction IDs
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