[IMAP-372] Deadlock in AbstractDelegatingMailboxListener under load

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.3
• Component/s: Mailbox
• Assignee: Eric Charles
• Reporter: Andrzej Rusin
• Created: 09/Apr/13 15:07
• Updated: 03/Feb/14 14:49
• Resolved: 26/Apr/13 12:45

Description

In AbstractDelegatingMailboxListener::event, firing the events inside the synchronized blocks causes a deadlock involving:

lock on HashMapDelegatingMailboxListener::listeners
(synchronized methods) lock on SelectedMailboxImpl

In my example, these 3 methods got interlocked:
AbstractDelegatingMailboxListener.addListener
SelectedMailboxImpl.msn
AbstractDelegatingMailboxListener.removeListener

My idea to fix it is basically to take the for loop on mListeners outside the synchronized block in org.apache.james.mailbox.store.AbstractDelegatingMailboxListener.event(Event). That will not make the propagated event processing in SelectedMailboxImpl hit the synchronized lock on listeners.

Issue Links

• is related to: JAMES-1411 PathLocker may cause deadlocks
• is related to: MAILBOX-183 readUidFile is taking too much time for large uid file and blocks other threads