[HDFS-862] Potential NN deadlock in processDistributedUpgradeCommand

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: 0.22.0, 0.23.1
• Component/s: namenode
• Assignee: Unassigned
• Reporter: Todd Lipcon
• Created: 29/Dec/09 16:56
• Updated: 29/Jul/14 21:41
• Resolved: 29/Jul/14 21:41

Description

Haven't seen this in practice, but the lock order is inconsistent. processReport locks FSNamesystem, then calls UpgradeManager.startUpgrade, getUpgradeState, and getUpgradeStatus (each of which locks the UpgradeManager). FSNameSystem.processDistributedUpgradeCommand calls upgradeManager.processUpgradeCommand which is synchronized on UpgradeManager, which can call FSNameSystem.leaveSafeMode which synchronizes on FSNamesystem.