hadoop-mapreduce-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1436) Deadlock in preemption code in fair scheduler
Date Wed, 17 Feb 2010 06:52:28 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1436?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12834665#action_12834665

Todd Lipcon commented on MAPREDUCE-1436:

Hi Matei,

I don't think this issue actually occurs in trunk - I'm speaking now about the top issue from
this issue involving finalizeJob. MAPREDUCE-870 refactored this stuff, and finalizeJob therefore
no longer has to go "upwards" to the scheduler lock.

I turned on preemption and ran a couple of sleep jobs under jcarder, and it didn't identify
this issue either. Just to sanity check myself, I added a synchronized (taskTrackerScheduler)
{ System.err.println("hi"); } in the finalizeJob method, and reran the test. jcarder spit
out the expected potential deadlock just like you saw it.

I think, really, the JT was at fault here for inverting the lock heirarchy. It no longer does
this, so I think we're safe without this patch.

What do you think?

> Deadlock in preemption code in fair scheduler
> ---------------------------------------------
>                 Key: MAPREDUCE-1436
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1436
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: contrib/fair-share
>    Affects Versions: 0.21.0, 0.22.0
>            Reporter: Matei Zaharia
>            Assignee: Matei Zaharia
>            Priority: Blocker
>         Attachments: deadlock.png, mapreduce-1436-v2.patch, mapreduce-1436.patch
> In testing the fair scheduler with preemption, I found a deadlock between updatePreemptionVariables
and some code in the JobTracker. This was found while testing a backport of the fair scheduler
to Hadoop 0.20, but it looks like it could also happen in trunk and 0.21. Details are in a
comment below.

This message is automatically generated by JIRA.
You can reply to this email to add a comment to the issue online.

View raw message