[MAPREDUCE-1342] Potential JT deadlock in faulty TT tracking

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.20.1
• Fix Version/s: 0.21.0
• Component/s: jobtracker
• Hadoop Flags: Reviewed
• Release Note: Fix for a potential deadlock in the global blacklist of tasktrackers feature.
• Assignee: Amareshwari Sriramadasu
• Reporter: Todd Lipcon
• Created: 29/Dec/09 02:05
• Updated: 24/Aug/10 21:19
• Resolved: 19/Jan/10 10:21

Description

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.