Bug 1293229 – RCU stalls message on realtime kernel

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Bug 1293229 - RCU stalls message on realtime kernel

Summary:	RCU stalls message on realtime kernel

Status:	CLOSED ERRATA

Aliases:	None

Product:	Red Hat Enterprise Linux 7
Classification:	Red Hat
Component:	kernel-rt (Show other bugs)
Sub Component:
Version:	7.3
Hardware:	x86_64 Linux

Priority	high Severity high
Target Milestone:	rc
Target Release:	---
Assigned To:	Luis Claudio R. Goncalves
QA Contact:
Docs Contact:

URL:
Whiteboard:
Keywords:	ZStream

Depends On:	1292927
Blocks:	1295885
	Show dependency tree / graph

Reported:	2015-12-21 02:06 EST by Jan Kurik
Modified:	2016-02-16 05:49 EST (History)
CC List:	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
Clones:	1295885 (view as bug list)
Environment:
Last Closed:	2016-02-16 05:49:54 EST
Type:	---
Regression:	---
Mount Type:	---
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
Add an attachment (proposed patch, testcase, etc.)

External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Red Hat Product Errata	RHSA-2016:0212	normal	SHIPPED_LIVE	Important: kernel-rt security, bug fix, and enhancement update	2016-02-16 10:46:40 EST

Groups: 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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