Bug 1640875

Summary:	ofproto-dpif-xlate: Avoid deadlock on multicast snooping recursion.
Product:	Red Hat OpenStack	Reporter:	Brendan Shephard <bshephar>
Component:	openvswitch	Assignee:	Assaf Muller <amuller>
Status:	CLOSED CURRENTRELEASE	QA Contact:	Eran Kuris <ekuris>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	13.0 (Queens)	CC:	aguetta, amuller, apevec, chrisw, fleitner, jlibosva, rhos-maint
Target Milestone:	---	Keywords:	Triaged, ZStream
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:
Clones:	1640930 1643065 (view as bug list)		Environment:
Last Closed:	2020-02-25 14:25:17 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:	1643071
Bug Blocks:

Description Brendan Shephard 2018-10-19 03:36:19 UTC

Description of problem:
Issue: https://github.com/openvswitch/ovs-issues/issues/153
Copied from the github issue: https://github.com/openvswitch/ovs/commit/ed56f8bd6a668df3664f68b00c5396c268aa1821

Until now, OVS did multicast snooping outputs holding the read-lock on
the mcast_snooping object.  This could recurse via a patch port to try to
take the write-lock on the same object, which deadlocked.  This patch fixes
the problem, by releasing the read-lock before doing any outputs.

It would probably be better to use RCU for mcast_snooping.  That would be
a bigger patch and less suitable for backporting.

Version-Release number of selected component (if applicable):
2.9

How reproducible:


Steps to Reproduce:
1.
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Actual results:


Expected results:


Additional info:
Creating this BZ to address customer concern about upstream issue that has recently been patched. Looking to backport the fix into RHEL OvS release for OpenStack.

Comment 3 Flavio Leitner 2018-10-25 13:05:42 UTC

Looks like the patch is backported in upstream already, so I opened the RHEL bugs to track the backport. I am proposing for the next batch FDP:18.12.

2.10 https://bugzilla.redhat.com/show_bug.cgi?id=1643065
2.9 https://bugzilla.redhat.com/show_bug.cgi?id=1643071