Bugzilla – Full Text Bug Listing
| Summary: | Deadlock on Display.syncExec() | ||
|---|---|---|---|
| Product: | [Modeling] EMF | Reporter: | Martin Fluegge <martin.fluegge> |
| Component: | cdo.core | Assignee: | Eike Stepper <stepper> |
| Status: | CLOSED FIXED | QA Contact: | Eike Stepper <stepper> |
| Severity: | normal | ||
| Priority: | P3 | CC: | give.a.damus, vincent.hemery |
| Version: | 4.5 | ||
| Target Milestone: | --- | ||
| Hardware: | PC | ||
| OS: | Windows XP | ||
| Whiteboard: | |||
| Bug Depends on: | 340709 | ||
| Bug Blocks: | |||
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Description
Martin Fluegge
I have also encountered freezes while developping a component ontop of CDO.
Trying to debug the freeze, I happened to give a closer look at the following method, in which invalidation often calls graphical refresh (hence sync with UI Display):
org.eclipse.emf.internal.cdo.view.CDOViewImpl.doInvalidate(CDOBranch, long, List<CDORevisionKey>, List<CDOIDAndVersion>, Map<CDOID, InternalCDORevision>)
This method is synchronized. Yet, I think this is not enough.
While debugging it, I had this method called on both a transaction and a view. Hence, the "detachedObjects" variable can get filled for both before the conflicts and notifications are handled.
Instead of a synchronized method (which synchronizes on the this instance), you should probably use "synchronized(CDOViewImpl.class) {" to avoid this.
The fact that I had breakpoints must have helped provoking these freezes. And so does probably SWTBot.
Moving all open bug reports to 4.1 because the release is very near and it's hghly unlikely that there will be spare time to address 4.0 problems. Please make sure that your patches can be applied against the master branch and that your problem is not already fixed there!!! Moving all open issues to 4.2. Open bugs can be ported to 4.1 maintenance after they've been fixed in master. I can easily reproduce this in the Juno Modeling Package with Dawn installed. I suggest that it has at least Major severity, if not Critical, because this will make it very hard to integrate Dawn into CDO-based applications. Basically, in a Dawn context, one must use Dawn's API (on the UI thread?) to commit transactions. Committing using the CDO API causes deadlock. Steps to reproduce 100% of the time: 0. Start a CDO Server instance on H2 database. 1. Launch your CDO/Dawn Juno workbench. 2. Create a new Dawn Acore diagram. Add a class to the diagram and name it "Foo." 3. ** Don't save the editor **. 4. Switch to the CDO Sessions view and find the dirty transaction that the Dawn Acore editor is using. Context-click it and select "Commit". 5. Observe the deadlock. On Mac OS X, it manifests as a SPOD. The deadlock is between: * a runnable on the UI thread waiting for a CDOTransaction monitor (trying to get the eResource() of an EObject, which the CDOStoreImpl does under synchronization on its view) * CDO's commit job, waiting for the UI thread's runnable lock. This job is notifying listeners that commit completed. The CDOResourceImpl changes its isModified state to false (saved), which notifies the DawnTransactionChangeRecorder. This, in turn, tells GMF's DiagramEventBroker that the diagram has been saved, and the broker tries to update the UI in a synchronous runnable I copy the relevant stack traces, below. Note that on Mac OS X, the UI thread is not the main thread, but Thread-1. The main thread is native code. Daemon Thread [Thread-1] (Suspended) owns: RunnableLock (id=73) waiting for: CDOTransactionImpl (id=72) CDOStoreImpl.getResource(InternalEObject) line: 157 CDOResourceImpl(CDOObjectImpl).eDirectResource() line: 481 CDOResourceImpl.eDirectResource() line: 205 CDOResourceImpl(BasicEObjectImpl).eInternalResource() line: 925 CDOResourceImpl(CDOObjectImpl).eInternalResource() line: 492 CDOResourceImpl(BasicEObjectImpl).eResource() line: 920 AcorePropertySection(AbstractModelerPropertySection).isNotifierDeleted(Notification) line: 506 AdvancedPropertySection$1.run() line: 215 RunnableLock.run() line: 35 UISynchronizer(Synchronizer).runAsyncMessages(boolean) line: 135 Display.runAsyncMessages(boolean) line: 3944 Display.readAndDispatch() line: 3621 ... Thread [Worker-1] (Suspended) owns: CDOTransactionImpl (id=72) waiting for: Semaphore (id=81) Object.wait(long) line: not available [native method] Semaphore.acquire(long) line: 43 UISynchronizer.syncExec(Runnable) line: 168 Display.syncExec(Runnable) line: 4605 DiagramEventBrokerThreadSafe.resourceSetChanged(ResourceSetChangeEvent) line: 63 DiagramEditingDomainFactory$DiagramEditingDomain$2.run() line: 167 DawnDiagramEditingDomainFactory$DawnDiagramEditingDomain(TransactionalEditingDomainImpl).runExclusive(Runnable) line: 328 DawnDiagramEditingDomainFactory$DawnDiagramEditingDomain(DiagramEditingDomainFactory$DiagramEditingDomain).broadcastUnbatched(Notification) line: 163 DawnTransactionChangeRecorder(TransactionChangeRecorder).appendNotification(Notification) line: 319 DawnTransactionChangeRecorder(TransactionChangeRecorder).processResourceNotification(Notification) line: 272 DawnTransactionChangeRecorder(TransactionChangeRecorder).notifyChanged(Notification) line: 238 DawnTransactionChangeRecorder.notifyChanged(Notification) line: 44 CDOResourceImpl(BasicNotifierImpl).eNotify(Notification) line: 374 CDOResourceImpl.setModified(boolean) line: 396 CDOModificationTrackingAdapter$1.committedTransaction(CDOTransaction, CDOCommitContext) line: 45 CDOTransactionImpl$CDOCommitContextImpl.postCommit(CDOSessionProtocol$CommitTransactionResult) line: 2893 CDOSingleTransactionStrategyImpl.commit(InternalCDOTransaction, IProgressMonitor) line: 74 CDOTransactionImpl.commit(IProgressMonitor) line: 1144 CDOTransactionImpl.commit() line: 1164 CommitTransactionAction.doRun(IProgressMonitor) line: 38 LongRunningAction$1.run(IProgressMonitor) line: 185 Worker.run() line: 54 With Kepler post-M4 CDO I'm still getting this deadlock. Today, it's a different call stack on the UI thread trying to synchronized on the CDOView (below). The DiagramEventBroker::resourceSetChanged(...) method is processing an notification from a CDOResource (modified state changed) in a block of code guarded by an "notifier instance of EObject" check. I'm not sure that we still wouldn't deadlock on some other object if the event broker checked explicitly for "!(notifier instanceof Resource)". I'm going to try to compare against what happens when committing the transaction from the Dawn UI, because I don't know why that doesn't deadlock in the same way (seems like an inevitable deadlock between the worker thread committing the transaction and the UI thread which doesn't know that it has to synchronize on the CDOView to access basic EMF properties like eContainer). -------- 8< -------- Daemon Thread [Thread-1] (Suspended) owns: RunnableLock (id=75) waiting for: CDOTransactionImpl (id=74) CDOStoreImpl.getContainer(InternalEObject) line: 123 CDOResourceImpl(CDOObjectImpl).eInternalContainer() line: 619 CDOResourceImpl(BasicEObjectImpl).eContainer() line: 765 DiagramEventBrokerThreadSafe(DiagramEventBroker).getInterestedNotificationListeners(Notification, DiagramEventBroker$NotifierToKeyToListenersSetMap) line: 753 DiagramEventBrokerThreadSafe(DiagramEventBroker).fireNotification(Notification) line: 497 DiagramEventBrokerThreadSafe(DiagramEventBroker).resourceSetChanged(ResourceSetChangeEvent) line: 399 DiagramEventBrokerThreadSafe.internal_resourceSetChanged(ResourceSetChangeEvent) line: 84 DiagramEventBrokerThreadSafe.access$0(DiagramEventBrokerThreadSafe, ResourceSetChangeEvent) line: 83 DiagramEventBrokerThreadSafe$1.run() line: 65 ... I just realized I've hijacked this bug with a different problem. I'll raise a new one. We'll try to address open problems in 4.3 (master) first and then port fixes back to 4.2. Moving all open bugzillas to 4.5. Christian, do you know how to create an Acore diagram with Mars or Neon? (In reply to Eike Stepper from comment #9) > Christian, do you know how to create an Acore diagram with Mars or Neon? Do you not have the New Acore Diagram option in the New Wizard? Perhaps you don't have the *.acore* bundles in your PDE Target or workspace? I'll generalize this bugzilla to "Deadlock on Display.syncExec()". A general solution will follow ASAP... Moving all unaddressed bugzillas to 4.6. The changes were committed to master in January 2016: 5c0eface8b30653f24895d753ed1dee469f17d2b be45bd8af72711993c5c1777bf755a9506c5a90c Closing. Closing. |