[JCR-2753] Deadlock in DefaultISMLocking

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.0.5, 2.1.3, 2.2
• Component/s: jackrabbit-core
• Assignee: Thomas Mueller
• Reporter: Thomas Mueller
• Created: 21/Sep/10 10:02
• Updated: 08/Dec/10 19:26
• Resolved: 21/Sep/10 10:13

Description

There seems to be a bug in DefaultISMLocking which was detected as part of JCR-2746.

1) The main thread gets a read lock.

2) The ObservationManager thread tries to lock for writing, which is blocked because there is still a read lock.

3) Then the main thread tries to get a second read lock, which is blocked because there is a waiting write lock.

The bug was introduced as part of JCR-2089 (Use java.util.concurrent), revisions 995411 and 995412. I think the safe solution is to revert those to commits, and add a test case. If the DefaultISMLocking is changed later on, more test cases are required. An efficient solution is relatively complicated.