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Bug 1894587 - lru-add-drain workqueue on RT is allocated without being used
Summary: lru-add-drain workqueue on RT is allocated without being used
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: kernel-rt
Version: 7.9
Hardware: x86_64
OS: Linux
unspecified
medium
Target Milestone: rc
: ---
Assignee: Juri Lelli
QA Contact: Mark Simmons
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2020-11-04 15:00 UTC by Juri Lelli
Modified: 2023-08-08 03:01 UTC (History)
6 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2021-06-08 22:33:36 UTC
Target Upstream Version:
Embargoed:


Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Gitlab redhat/rhel/src/kernel rhel-7 merge_requests 59 0 None None None 2021-03-30 09:40:30 UTC
Gitlab redhat/rhel/src/kernel rhel-7 merge_requests 68 0 None None None 2021-04-02 09:21:26 UTC

Description Juri Lelli 2020-11-04 15:00:45 UTC
Description of problem:
A customer (AltioStar, this is related to bz1886312) asked for clarifications about
lru-add-drain kthread. They were worried that it might cause latency spikes on isolated
cpus, as its affinity cannot be restricted to non-isolated cpus.

Investigation showed that, on RT kernel, this kthread is allocated (by the workqueue
subsystem), but never actually used since RT kernel doesn't use workqueues to perform
remote_lru_add_drain.

Even though there is practically no harm in creating such kthread, it would be good to
remove it as it creates confusion (at least).

Version-Release number of selected component (if applicable):
kernel-rt-3.10.0-1160.7.1.rt56.1140.el7

Comment 23 errata-xmlrpc 2021-06-08 22:33:36 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 (Important: kernel-rt security and bug fix update), 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-2021:2316


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