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Re: Deadlock ...
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Re: Deadlock ...

  • Subject: Re: Deadlock ...
  • From: Kieran Kelleher <email@hidden>
  • Date: Tue, 15 May 2007 06:43:14 -0400

The unchanged offending code is shown below the 4 stack traces. At the time, my app was on a long response page and the background thread (Thread [wk.cheetah.ShipRtbsCampaignsLRTask@640285]) hung when calling dispose on an editing context.

BTW, I see there is a EOSharedEditingContext lock in the first stack trace below, what has that got to do with my ec being locked ...... I recall discussion on the list about EOShared EC being bad and to "turn it off" .... would turning it off help and if so, how can I turn it off?

I will guess that it would help. Call ec.setSharedEditingContext (null). Are you using the shared EC at all?
Eliminated it after sending this post. No longer being used. I am hopeful that the shared ec elimination will solve. We'll just have to wait and see if lock timing during testing or real world use causes a deadlock at some time in the future.



The difficult part is that I can stop the app, run it again and I cannot reproduce this again right now with no code changes....

Which strongly points to concurrency and the EOF stack synchronizer as at least an involved party.


Skip down, the read back up.



Any suggestions on how to prevent this and make my code more robust?

	Thread [wk.cheetah.ShipRtbsCampaignsLRTask@640285] (Suspended)
		Object.wait(long) line: not available [native method]

6. Something else has the SEC locked for writing so this thread blocks 
		NSMultiReaderLock$ConditionLock(Object).wait() line: 474
		NSMultiReaderLock$ConditionLock.await() line: 506
		NSMultiReaderLock._lockForWriting() line: 204
		NSMultiReaderLock.lockForWriting() line: 165
		EOSharedEditingContext.lock() line: 700
		WKEditingContext(EOEditingContext).lockObjectStore() line: 4733

5. The change requires invalidating objects
WKEditingContext(EOEditingContext).refaultObject (EOEnterpriseObject, EOGlobalID, EOEditingContext) line: 4041
WKEditingContext(ERXEC).refaultObject(EOEnterpriseObject, EOGlobalID, EOEditingContext) line: 1064
WKEditingContext(EOEditingContext)._refaultObjectWithGlobalID (EOEnterpriseObject, EOGlobalID) line: 3293
WKEditingContext (EOEditingContext)._newChangesFromInvalidatingObjectsWithGlobalIDs (NSArray) line: 3522

4. There was a change to process:
WKEditingContext(EOEditingContext)._processObjectStoreChanges (NSDictionary) line: 3558
GeneratedMethodAccessor373.invoke(Object, Object[]) line: not available
DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: 25
Method.invoke(Object, Object...) line: 585
NSSelector.invoke(Object, Object[]) line: 354
NSSelector._safeInvokeSelector(NSSelector, Object, Object[]) line: 108

3. lock() processes pending notifications (e.g. from the EOF stack synchronizer:
Logically, one would expect that pending notifications would be ignored in an ec after dispose is called

WKEditingContext(EOEditingContext)._processNotificationQueue() line: 4810

2. Dispose locks the ec: 
		WKEditingContext(EOEditingContext).lock() line: 4688
		WKEditingContext(ERXEC).lock() line: 436

1. This is the dispose call:
WKEditingContext(EOEditingContext)._dispose(boolean) line: 1064
WKEditingContext(EOEditingContext).dispose() line: 1059
WKEditingContext(ERXEC).dispose() line: 574
ShipRtbsCampaignsLRTask.performAction() line: 97
ShipRtbsCampaignsLRTask(ERXLongResponseTask $DefaultImplementation).run() line: 163
ERXLongResponseTask$WorkerThread(Thread).run() line: 613
ERXLongResponseTask$WorkerThread.run() line: 60




Thread [Thread-1] (Suspended)
Object.wait(long) line: not available [native method]
NSMultiReaderLock$ConditionLock(Object).wait() line: 474
NSMultiReaderLock$ConditionLock.await() line: 506
NSMultiReaderLock._lockForWriting() line: 204
NSMultiReaderLock.lockForWriting() line: 165
EOSharedEditingContext.lock() line: 700
WKEditingContext(EOEditingContext).lockObjectStore() line: 4733
WKEditingContext(EOEditingContext)._processReferenceQueue() line: 4829
WKEditingContext(EOEditingContext)._processRecentChanges() line: 1930
WKEditingContext(EOEditingContext).processRecentChanges() line: 1951
WKEditingContext(ERXEC).processRecentChanges() line: 623
WKEditingContext(EOEditingContext)._processObjectStoreChanges (NSDictionary) line: 3536
GeneratedMethodAccessor373.invoke(Object, Object[]) line: not available
DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: 25
Method.invoke(Object, Object...) line: 585
NSSelector.invoke(Object, Object[]) line: 354
NSSelector._safeInvokeSelector(NSSelector, Object, Object[]) line: 108
WKEditingContext(EOEditingContext)._processNotificationQueue() line: 4810
WKEditingContext(EOEditingContext).lock() line: 4688
WKEditingContext(ERXEC).lock() line: 436
WKEditingContext(EOEditingContext).tryLock() line: 4700
WKEditingContext(EOEditingContext)._sendOrEnqueueNotification (NSNotification, NSSelector) line: 4774
WKEditingContext(EOEditingContext)._objectsChangedInStore (NSNotification) line: 3598
WKEditingContext(ERXEC)._objectsChangedInStore(NSNotification) line: 1241
GeneratedMethodAccessor372.invoke(Object, Object[]) line: not available
DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: 25
Method.invoke(Object, Object...) line: 585
NSSelector._safeInvokeMethod(Method, Object, Object[]) line: 120
NSNotificationCenter$_Entry.invokeMethod(NSNotification) line: 601
NSNotificationCenter.postNotification(NSNotification) line: 545
NSNotificationCenter.postNotification(String, Object, NSDictionary) line: 575
EOObjectStoreCoordinator._objectsChangedInSubStore (NSNotification) line: 744
GeneratedMethodAccessor376.invoke(Object, Object[]) line: not available
DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: 25
Method.invoke(Object, Object...) line: 585
NSSelector._safeInvokeMethod(Method, Object, Object[]) line: 120
NSNotificationCenter$_Entry.invokeMethod(NSNotification) line: 601
NSNotificationCenter.postNotification(NSNotification) line: 545
NSNotificationCenter.postNotification(String, Object, NSDictionary) line: 575
ERXObjectStoreCoordinatorSynchronizer$ProcessChangesQueue $InsertSnapshotProcessor.processSnapshots(EODatabaseContext, EODatabase, NSDictionary) line: 273
ERXObjectStoreCoordinatorSynchronizer $ProcessChangesQueue._process(EOObjectStoreCoordinator, EOObjectStoreCoordinator, NSMutableDictionary, ERXObjectStoreCoordinatorSynchronizer$ProcessChangesQueue $SnapshotProcessor, NSDictionary, String) line: 432
ERXObjectStoreCoordinatorSynchronizer$ProcessChangesQueue.process (EOObjectStoreCoordinator, ERXObjectStoreCoordinatorSynchronizer $ProcessChangesQueue$SnapshotProcessor, NSDictionary, String) line: 450
ERXObjectStoreCoordinatorSynchronizer$ProcessChangesQueue.run() line: 524
Thread.run() line: 613

I will leave that one to Mike. The ERXObjectStoreCoordinatorSynchronizer is processing a change and sending notifications. It also needs a write lock on the SEC and blocks because someone else has it.



Thread [WorkerThread3] (Suspended)
Object.wait(long) line: not available [native method]
NSRecursiveLock(Object).wait() line: 474
NSRecursiveLock.lock() line: 72
EOObjectStoreCoordinator.lock() line: 466
WKEditingContext(EOEditingContext).lockObjectStore() line: 4735
WKEditingContext(EOEditingContext)._processReferenceQueue() line: 4829
WKEditingContext(EOEditingContext)._processRecentChanges() line: 1930
WKEditingContext(EOEditingContext).processRecentChanges() line: 1951
WKEditingContext(ERXEC).processRecentChanges() line: 623
WKEditingContext(EOEditingContext)._processObjectStoreChanges (NSDictionary) line: 3536
GeneratedMethodAccessor373.invoke(Object, Object[]) line: not available
DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: 25
Method.invoke(Object, Object...) line: 585
NSSelector.invoke(Object, Object[]) line: 354
NSSelector._safeInvokeSelector(NSSelector, Object, Object[]) line: 108
WKEditingContext(EOEditingContext)._processNotificationQueue() line: 4810
WKEditingContext(EOEditingContext).lock() line: 4688
WKEditingContext(ERXEC).lock() line: 436
Session(WOSession)._awakeInContext(WOContext) line: 717
Application(WOApplication).restoreSessionWithID(String, WOContext) line: 1550
Application(ERXApplication).restoreSessionWithID(String, WOContext) line: 1335
WOComponentRequestHandler._dispatchWithPreparedApplication (WOApplication, WOContext, NSDictionary) line: 314
WOComponentRequestHandler._handleRequest(WORequest) line: 358
WOComponentRequestHandler.handleRequest(WORequest) line: 432
Application(WOApplication).dispatchRequest(WORequest) line: 1306
Application(ERXApplication).dispatchRequest(WORequest) line: 1117
Application.dispatchRequest(WORequest) line: 195
WOWorkerThread.runOnce() line: 173
WOWorkerThread.run() line: 254
Thread.run() line: 613


Late to the party, this one blocks locking the OSC which has been locked by another thread. I don't see it in the trace, but I am guessing that ERXObjectStoreCoordinatorSynchronizer has it locked while it processes the changes.


None of this answers the crucial question: who is holding the SEC writer lock?

Were there any exceptions that happened before this deadlock?

No, the app just froze and the meta-refresh page's R-R locked

Chuck






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References: 


 >Re: Deadlock ... (From: Kieran Kelleher <email@hidden>)


 >Re: Deadlock ... (From: Chuck Hill <email@hidden>)






    

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