hadoop-mapreduce-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Jothi Padmanabhan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1342) Potential JT deadlock in faulty TT tracking
Date Tue, 05 Jan 2010 07:22:54 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12796571#action_12796571
] 

Jothi Padmanabhan commented on MAPREDUCE-1342:
----------------------------------------------

Prior to the patch, all accesses to FaultInfo objects were synchronized on potentiallyFaultyTrackers
and so sort of internally synchronized themselves. However, we are relaxing that restriction
with this patch, atleast for isBlackListed and the reasonForBlacklisting. I think we should
guard the accesses to these variables or make them volatile, no?

> Potential JT deadlock in faulty TT tracking
> -------------------------------------------
>
>                 Key: MAPREDUCE-1342
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1342
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: jobtracker
>    Affects Versions: 0.22.0
>            Reporter: Todd Lipcon
>         Attachments: cycle0.png, mapreduce-1342-1.patch, mapreduce-1342-2.patch
>
>
> JT$FaultyTrackersInfo.incrementFaults first locks potentiallyFaultyTrackers, and then
calls blackListTracker, which calls removeHostCapacity, which locks JT.taskTrackers
> On the other hand, JT.blacklistedTaskTrackers() locks taskTrackers, then calls faultyTrackers.isBlacklisted()
which goes on to lock potentiallyFaultyTrackers.
> I haven't produced such a deadlock, but the lock ordering here is inverted and therefore
could deadlock.
> Not sure if this goes back to 0.21 or just in trunk.

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


Mime
View raw message