Bug 1293229 - RCU stalls message on realtime kernel
RCU stalls message on realtime kernel
Status: CLOSED ERRATA
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: kernel-rt (Show other bugs)
7.3
x86_64 Linux
high Severity high
: rc
: ---
Assigned To: Luis Claudio R. Goncalves
: ZStream
Depends On: 1292927
Blocks: 1295885
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Reported: 2015-12-21 02:06 EST by Jan Kurik
Modified: 2016-02-16 05:49 EST (History)
5 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Cause: A possible livelock in the NAPI polling and busy polling routines could lead the system to a livelock on threads running at high, realtime, priorities. Consequence: threads running at priorities lower than the ones of the threads involved in the livelock would be prevented from running on the CPUs affected by the livelock. Among those threads are the rcuc/ threads. Fix: right before (4 jiffies) a RCU stall is detected, the rcuc/ threads on the CPUs facing the livelock have their priorities boosted above the priority of the threads involved in the livelock. Also, the softirqs are now handled in a way closer to the behavior of the upstream kernel. Result: Even under pressure thre rcuc/ threads are able to run, mitigating the RCU stalls.
Story Points: ---
Clone Of: 1292927
: 1295885 (view as bug list)
Environment:
Last Closed: 2016-02-16 05:49:54 EST
Type: ---
Regression: ---
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Documentation: ---
CRM:
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---


Attachments (Terms of Use)
rcu: Boost rcuc if it has 4 jiffies before splatting (3.25 KB, patch)
2016-01-06 23:01 EST, Luis Claudio R. Goncalves
no flags Details | Diff
softirq: Perform softirqs in local_bh_enable() for a limited amount of time (3.63 KB, patch)
2016-01-06 23:02 EST, Luis Claudio R. Goncalves
no flags Details | Diff

  None (edit)
Description Jan Kurik 2015-12-21 02:06:33 EST
This bug has been copied from bug #1292927 and has been proposed
to be backported to 7.2 z-stream (EUS).
Comment 3 Luis Claudio R. Goncalves 2016-01-06 23:01 EST
Created attachment 1112334 [details]
rcu: Boost rcuc if it has 4 jiffies before splatting
Comment 4 Luis Claudio R. Goncalves 2016-01-06 23:02 EST
Created attachment 1112335 [details]
softirq: Perform softirqs in local_bh_enable() for a limited amount of time
Comment 9 errata-xmlrpc 2016-02-16 05:49:54 EST
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHSA-2016-0212.html

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