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Bug 647434

Summary: perf: Mark software events as irqsafe
Product: Red Hat Enterprise MRG Reporter: John Kacur <jkacur>
Component: realtime-kernelAssignee: John Kacur <jkacur>
Status: CLOSED ERRATA QA Contact: David Sommerseth <davids>
Severity: medium Docs Contact:
Priority: low    
Version: 1.3CC: bhu, lgoncalv, ovasik, williams
Target Milestone: ---   
Target Release: ---   
Hardware: Unspecified   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
* Cause: * Consequence: * Fix: * Result:
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Clone Of: Environment:
Last Closed: 2010-12-08 19:11:05 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
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Description Flags
bz647434-perf-Mark-software-events-as-irqsafe.patch none

Description John Kacur 2010-10-28 11:10:53 UTC 
From: Peter Zijlstra <peterz>

Noticed while using 'perf top' on a machine without a supported PMU on
2.6.33.7-rt29, when top falls back to using the "cpu-clock" software
event.

Reproduced on other machines where the problem was masked due to the
existence and use of hardware events, by explicitely asking for a
software event using:

perf top -e cpu-clock
Comment 1 John Kacur 2010-10-28 11:17:38 UTC 
Created attachment 456218 [details]
bz647434-perf-Mark-software-events-as-irqsafe.patch
Comment 3 Clark Williams 2010-11-22 22:28:26 UTC 
    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
* Cause: 
* Consequence: 
* Fix: 
* Result:
Comment 5 John Kacur 2010-11-24 20:27:04 UTC 
(In reply to comment #3)
>     Technical note added. If any revisions are required, please edit the
> "Technical Notes" field
>     accordingly. All revisions will be proofread by the Engineering Content
> Services team.
> 
>     New Contents:
> * Cause: 
> * Consequence: 
> * Fix: 
> * Result:

Cause: using 'perf top' on a machine without a supported PMU on
2.6.33.7-rt29, when top falls back to using the "cpu-clock" software
event.

Consequence: BUG: scheduling while atomic

Fix: Patch is attached to this bugzilla

Result: no BUG is triggered
Comment 6 David Sommerseth 2010-12-03 15:45:05 UTC 
Verified by code review and by running 'perf top'.

Found bz647434-perf-Mark-software-events-as-irqsafe.patch (mrg-rt-v2.git 8676f3c7afd090d5881b998e8e809d00546990e7) applied to kernel-rt-2.6.33.7-rt29.47.src.rpm.

When running 'perf top' on athlon4.rhts.eng.bos.redhat.com with -rt29.45 the box froze completely after a short time.  When running -rt29.47 'perf top' did it's job and the box did not freeze at all.
Comment 8 errata-xmlrpc 2010-12-08 19:11:05 UTC 
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2010-0958.html