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Cisco Bug: CSCta15807 - 12.2(33)SCB: PXF queues stuck with CIR queues configured

Last Modified

Jan 24, 2017

Products (1)

  • Cisco uBR10000 Series Universal Broadband Routers

Known Affected Releases

12.2(33)SCB1

Description (partial)

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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Bug Details Include

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