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https://issues.apache.org/jira/browse/MAPREDUCE-1342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12796996#action_12796996
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Amar Kamat commented on MAPREDUCE-1342:
---------------------------------------
What if we move the code from JobTracker.blacklistedTaskTrackers() to
FaultyTrackersInfo. Something like
{code}
FaultyTrackersInfo {
blacklistedTaskTrackers {
synchronized (potentiallyFaultyTrackers) {
synchronized (taskTrackers) {
// code that we have today JobTracker.blacklistedTaskTrackers()
for (TaskTracker tt : taskTrackers.values()) {
// ...
}
}
}
}
}
blacklistedTaskTrackers() {
return FaultyTrackersInfo.blacklistedTaskTrackers()
}
{code}
This kindof solves the lock reversal issue we are facing now and also makes
more sense because JobTracker.FaultyTrackersInfo is the right module to answer
the blacklistedTaskTrackers() query. Thoughts?
> 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.
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