Cisco Bug: CSCta15807 - 12.2(33)SCB: PXF queues stuck with CIR queues configured
Jan 24, 2017
- Cisco uBR10000 Series Universal Broadband Routers
Known Affected Releases
Symptom: A number of customer scenarios have been seen recently running various flavors of 12.2SCB based images where pxf output queues become stuck. Dequeue counts stop incrementing for the queue, the queue fills up and eventually begins to tail drop. This has been seen on both cable interfaces as well as GE interfaces. In some instances the entire interface appears to be stuck. Often data corruption messages similar to the following are observed on the system: %DATACORRUPTION-1-DATAINCONSISTENCY: Doubly-linked list corruption Additionally, it is possible to sometimes see duplicate QID messages similar to the following: %GENERAL-2-CRITEVENT: duplicate qid Conditions: We believe that most if not all of these issues are the result of two bugs that have been identified in the toaster client. Both of these bugs cause corruption in the IOS maintained free and active lists for QIDs. The first occurs because of a bondry condition error in the code that returns a qtype from a QID. The result is that the last QID in the CIR pool (131071) is treated as a best effort QID by some pieces of code, and eventually returned to the BE free list instead of the CIR free list. The second bug places interface pak priority queues on the CIR active list instead of the BE active list (pak priority queue were at one point going to be CIR queues). This results in issues when the QIDs are eventually freed. In both cases list corruption occurs which can lead to incorrect programming in toaster and potential duplicate QID problems. The stuck queues are believed to be the result of mismatched flag settings in toaster as a result of the corrupted lists. Note that the first bug will only be observed once the complete CIR QID pool has been used at least one time (such that CIR QID 131071 gets allocated. The second problem can only be observed if interfaces are removed (such as through an OIR and subsequent config removal). We also believe that customers must have CIR queues configured to see these problems.
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