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Bug 2143719 - numad freezes during multiple access
Summary: numad freezes during multiple access
Keywords:
Status: CLOSED MIGRATED
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: numad
Version: 8.6
Hardware: x86_64
OS: Linux
unspecified
high
Target Milestone: rc
: ---
Assignee: Lukáš Nykrýn
QA Contact: qe-baseos-daemons
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2022-11-17 16:20 UTC by Ajeco Support
Modified: 2023-09-21 09:56 UTC (History)
1 user (show)

Fixed In Version:
Doc Type: ---
Doc Text:
Clone Of:
Environment:
Last Closed: 2023-09-21 09:56:19 UTC
Type: Bug
Target Upstream Version:
Embargoed:
pm-rhel: mirror+

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Issue Tracker   RHEL-5780 0 None Migrated None 2023-09-21 09:56:15 UTC
Red Hat Issue Tracker RHELPLAN-139824 0 None None None 2022-11-17 16:24:33 UTC

Description Ajeco Support 2022-11-17 16:20:53 UTC 
Description of problem:
numad -w will occasionally freeze if invoked concurrently with the numad daemon running

Version-Release number of selected component (if applicable):
0.5-26.20150602git

How reproducible:
Always

Steps to Reproduce:
1.Execute numad -w 4:4096 from multiple concurrent sessions. A good command line is: while true; do numad -w 4:4096; numad -w 4:4096; numad -w 4:4096; done

2.Wait for some time. Perhaps restart the command sequence to create a suitable timing skew.
3.

Actual results:
You will see one of the sessions freezing after a while

Expected results:
The sequence should run smoothly

Additional info:

This problem appeared during concurrent migration of several (n>3) VM:s in a KVM cluster. The VM:s had a numatune section looking like this:

  <vcpu placement='auto'>8</vcpu>
  <numatune>
    <memory mode='strict' placement='auto'/>
  </numatune>

libvirt tried to use numad -w 8:4096 to figure out the placement and the freeze of numad would also freeze libvirtd, which led to pcs rebooting the node.

Looking at the source of numad it seems like the potential problem is that each instance of numad will run init_msg_queue() at invocation. As this also does a flush_msg_queue() the queue will be emptied at every invocation. If this happens in the middle of the send/rcv-sequence of another invocation the other process will never get an answer and hang.
Comment 1 dag 2022-11-18 05:10:52 UTC 
Actually therea are two flaws in numad:
1. Only the daemon should flush the queue at init
2. There should be a timeout mechanism in the recieve message from ipc function

It should also be considered if there is a risk of the first invocation wrongly being seen as a daemon if we have multiple concurrent numad -w invocations. Havenät had the time to look into the daemon detection code.
Comment 2 RHEL Program Management 2023-09-21 09:55:58 UTC 
Issue migration from Bugzilla to Jira is in process at this time. This will be the last message in Jira copied from the Bugzilla bug.
Comment 3 RHEL Program Management 2023-09-21 09:56:19 UTC 
This BZ has been automatically migrated to the issues.redhat.com Red Hat Issue Tracker. All future work related to this report will be managed there.

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