[CAY-957] Deadlock in nested contexts

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.2 branch, 2.0 branch, 3.0
• Fix Version/s: 3.1B2, 3.2.M1
• Component/s: Core Library
• Assignee: Andrus Adamchik
• Reporter: Andrus Adamchik
• Created: 09/Jan/08 12:57
• Updated: 02/May/13 02:29
• Resolved: 11/Sep/12 01:30

Description

There is a deadlock condition when two peer nested contexts commit simultaneously. The test case (attached as a patch) deadlocks almost immediately with only two threads...

The old (pre CAY-1653 stack) :

Name: UpdateThread-9684455
State: BLOCKED on org.apache.cayenne.event.DispatchQueue@f899e9 owned by: UpdateThread-10872036
Total blocked: 7 Total waited: 1

Stack trace:
org.apache.cayenne.event.DispatchQueue.dispatchEvent(DispatchQueue.java:54)
org.apache.cayenne.event.EventManager.dispatchEvent(EventManager.java:348)
org.apache.cayenne.event.EventManager.postEvent(EventManager.java:319)
org.apache.cayenne.access.DataContext.fireDataChannelChanged(DataContext.java:1457)
org.apache.cayenne.access.DataContext.onContextFlush(DataContext.java:1121)
org.apache.cayenne.access.DataContext.onSync(DataContext.java:1102)
org.apache.cayenne.access.DataContext.flushToParent(DataContext.java:1160)
org.apache.cayenne.access.DataContext.commitChanges(DataContext.java:1073)
org.test.Main$UpdateThread.run(Main.java:66)

Name: UpdateThread-10872036
State: BLOCKED on org.apache.cayenne.access.ObjectStore@1b9b03 owned by: UpdateThread-9684455
Total blocked: 9 Total waited: 0

Stack trace:
org.apache.cayenne.access.DataContextMergeHandler.graphChanged(DataContextMergeHandler.java:104)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.apache.cayenne.util.Invocation.fire(Invocation.java:204)
org.apache.cayenne.event.EventManager$Dispatch.fire(EventManager.java:409)
org.apache.cayenne.event.DispatchQueue.dispatchEvent(DispatchQueue.java:162)
org.apache.cayenne.event.DispatchQueue.dispatchEvent(DispatchQueue.java:58)
org.apache.cayenne.event.EventManager.dispatchEvent(EventManager.java:348)
org.apache.cayenne.event.EventManager.postEvent(EventManager.java:319)
org.apache.cayenne.access.DataContext.fireDataChannelChanged(DataContext.java:1457)
org.apache.cayenne.access.DataContext.onContextFlush(DataContext.java:1121)
org.apache.cayenne.access.DataContext.onSync(DataContext.java:1102)
org.apache.cayenne.access.DataContext.flushToParent(DataContext.java:1160)
org.apache.cayenne.access.DataContext.commitChanges(DataContext.java:1073)
org.test.Main$UpdateThread.run(Main.java:66)

Newer stack is shown below in comments.

Issue Links

• depends upon: CAY-1653 Improving DefaultEventManager concurrency - non-bocking DispatchQueue
• is blocked by: CAY-1737 ObjectContexts listening to DataChannel events must be non-blocking
• is related to: CAY-1652 Deadlock within DefaultEventManager while creating a new ObjectContext
• relates to: CAY-720 While using nested DataContexts contexts and while a child commits to parent, parent is being refreshed via an event, resulting in a deadlock.