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Bug 1536370

Summary:	If IRQ disappears and reappears later the IRQ is not balanced correctly due to overflow in irq_count
Product:	Red Hat Enterprise Linux 6	Reporter:	Welterlen Benoit <bwelterl>
Component:	irqbalance	Assignee:	Petr Oros <poros>
Status:	CLOSED ERRATA	QA Contact:	Evan McNabb <emcnabb>
Severity:	high	Docs Contact:	Petr Bokoc <pbokoc>
Priority:	urgent
Version:	6.7	CC:	fkrska, jbainbri, jdluhos, jeder, pbokoc, skozina, toneata
Target Milestone:	rc	Keywords:	ZStream
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	irqbalance-1.0.7-9.el6	Doc Type:	Bug Fix
Doc Text:	Previously, if a device disappeared and then reappeared, the "irq_count" interrupt request (IRQ) counter in irqbalance overflowed, which resulted in a failure to balance IRQs. This update adds a check which triggers a rescan of the IRQ database if the counter decreases. As a result, IRQs remain correctly balanced for disappearing and reappearing devices.	Story Points:	---
Clone Of:
Clones:	1536373 1541290 1541293 (view as bug list)		Environment:
Last Closed:	2018-06-19 05:19:19 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:	1536373, 1541290, 1541293

Description Welterlen Benoit 2018-01-19 09:14:43 UTC

Description of problem:

If IRQ disappears and reappears later the IRQ is not balanced correctly due to overflow in irq_count (as the counter got smaller and difference cause overflow).
Rescan if this happens fix the problem.

Version-Release number of selected component (if applicable):
irqbalance-1.0.7-8

How reproducible:
Reproducible when a device disappears and reappears, for example when vm has high network load on aws vms with an enavf device

Steps to Reproduce:
1. Make a device disappears and reappears
2.
3.

Actual results:
the IRQ is not balanced correctly when a device disappears and reappears


Expected results:
the IRQ is balanced correctly


Additional info:
ENA driver resets look like they deassign and reassign the IRQs thus resetting counts.
This is fixed in version 1.0.8 thanks to this patch "Balance correctly IRQs reappearing" :
https://github.com/Irqbalance/irqbalance/commit/93ed80181e0ce7b81bc88a67fabad1ad829fc460

Comment 14 errata-xmlrpc 2018-06-19 05:19:19 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/RHBA-2018:1896