Bug 1427647

Summary:	[rt] dump stack: don't disable preemption during trace
Product:	Red Hat Enterprise Linux 7	Reporter:	Clark Williams <williams>
Component:	kernel-rt	Assignee:	Luis Claudio R. Goncalves <lgoncalv>
kernel-rt sub component:	Memory Management	QA Contact:	Jiri Kastner <jkastner>
Status:	CLOSED ERRATA	Docs Contact:
Severity:	medium
Priority:	low	CC:	bhu, williams
Version:	7.4
Target Milestone:	rc
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2017-08-01 19:00:29 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1353018, 1410158

Description Clark Williams 2017-02-28 20:03:36 UTC

We see large latencies during a stack dump on x86. The
preempt_disable() and get_cpu() should forbid moving the task to another
CPU during a stack dump and avoiding two stack traces in parallel on the
same CPU. However a stack trace from a second CPU may still happen in
parallel. Also nesting is allowed so a stack trace happens in
process-context and we may have another one from IRQ context. With migrate
disable we keep this code preemptible and allow a second backtrace on
the same CPU by another task.

Comment 7 errata-xmlrpc 2017-08-01 19:00:29 UTC

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://access.redhat.com/errata/RHSA-2017:2077

Comment 8 errata-xmlrpc 2017-08-02 00:24:28 UTC

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://access.redhat.com/errata/RHSA-2017:2077