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https://issues.apache.org/jira/browse/FELIX-3910?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13590642#comment-13590642
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Pierre De Rop commented on FELIX-3910:
--------------------------------------
Thanks for looking at the patch;
I do agree, the synchronize block might be problematic. Initially, I did not
think about any problems because I'm executing the serial executor outside the
synchronized block.
But one of the components may execute its serial executor, and in this case
some runnables may be executed while still holding the lock ...
I did this synchronization in order to avoid a race condition when multiple
services are registered concurrently (when the
ServiceDependencyImpl.addedService is called concurrently).
Indeed, If many services are registered concurrently, then we have to ensure
that we always call "ds.dependencyAvailable(ServiceDependencyImpl.this);"
before "ds.dependencyChanged(ServiceDependencyImpl.this);" ...
> Race conditions in DependencyManager
> ------------------------------------
>
> Key: FELIX-3910
> URL: https://issues.apache.org/jira/browse/FELIX-3910
> Project: Felix
> Issue Type: Bug
> Components: Dependency Manager
> Affects Versions: dependencymanager-3.0.0
> Environment: jdk1.6, jdk1.7, linux fc16
> Reporter: Pierre De Rop
> Attachments: FELIX-3910-patch
>
>
> In a multi threaded context, where dependencies are injected concurrently
> from different threads, we came across some exceptions which seem to take
> place from dependencymanager.
> I have tried to reproduce the problems using a paxexam test which I will
> commit.
> Not all exceptions are reproduced by the test case, but I think that the
> testcase really reproduces a problem.
> I also have a candidate patch, which I will submit to this jira issue.
> Here are the exceptions we have seen:
> first stacktrace seen:
> ===============
> ERROR: Bundle test.dm [21] EventDispatcher: Error during dispatch.
> (java.lang.NullPointerException)
> java.lang.NullPointerException
> at
> org.apache.felix.dm.impl.dependencies.ServiceDependencyImpl.addedService(ServiceDependencyImpl.java:481)
> at
> org.apache.felix.dm.tracker.ServiceTracker$Tracked.customizerAdded(ServiceTracker.java:1325)
> at
> org.apache.felix.dm.tracker.AbstractTracked.trackAdding(AbstractTracked.java:290)
> at
> org.apache.felix.dm.tracker.AbstractTracked.track(AbstractTracked.java:236)
> at
> org.apache.felix.dm.tracker.ServiceTracker$Tracked.serviceChangedHideAspects(ServiceTracker.java:1206)
> at
> org.apache.felix.dm.tracker.ServiceTracker$Tracked.serviceChanged(ServiceTracker.java:1101)
> at
> org.apache.felix.framework.util.EventDispatcher.invokeServiceListenerCallback(EventDispatcher.java:932)
> at
> org.apache.felix.framework.util.EventDispatcher.fireEventImmediately(EventDispatcher.java:793)
> at
> org.apache.felix.framework.util.EventDispatcher.fireServiceEvent(EventDispatcher.java:543)
> at org.apache.felix.framework.Felix.fireServiceEvent(Felix.java:4260)
> at org.apache.felix.framework.Felix.registerService(Felix.java:3275)
> at
> org.apache.felix.framework.BundleContextImpl.registerService(BundleContextImpl.java:346)
> at
> org.apache.felix.framework.BundleContextImpl.registerService(BundleContextImpl.java:320)
> at test.dm.race.RaceTest$RegistrationHelper$1.run(RaceTest.java:104)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:662)
> second exceptions:
> ==============
> ERROR: EventDispatcher: Error during dispatch.
> (java.lang.NullPointerException)
> java.lang.NullPointerException
> at
> org.apache.felix.dm.impl.ComponentImpl.invokeCallbackMethod(ComponentImpl.java:686)
> at
> org.apache.felix.dm.impl.dependencies.ServiceDependencyImpl.invoke(ServiceDependencyImpl.java:704)
> at
> org.apache.felix.dm.impl.dependencies.ServiceDependencyImpl.invokeRemoved(ServiceDependencyImpl.java:666)
> at
> org.apache.felix.dm.impl.dependencies.ServiceDependencyImpl.removedService(ServiceDependencyImpl.java:520)
> at
> org.apache.felix.dm.tracker.ServiceTracker$Tracked.customizerRemoved(ServiceTracker.java:1351)
> at
> org.apache.felix.dm.tracker.AbstractTracked.untrack(AbstractTracked.java:359)
> at
> org.apache.felix.dm.tracker.ServiceTracker$Tracked.serviceChangedHideAspects(ServiceTracker.java:1285)
> at
> org.apache.felix.dm.tracker.ServiceTracker$Tracked.serviceChanged(ServiceTracker.java:1101)
> at
> org.apache.felix.framework.util.EventDispatcher.invokeServiceListenerCallback(EventDispatcher.java:878)
> at
> org.apache.felix.framework.util.EventDispatcher.fireEventImmediately(EventDispatcher.java:732)
> at
> org.apache.felix.framework.util.EventDispatcher.fireServiceEvent(EventDispatcher.java:662)
> at org.apache.felix.framework.Felix.fireServiceEvent(Felix.java:3587)
> at org.apache.felix.framework.Felix.access$000(Felix.java:40)
> at org.apache.felix.framework.Felix$1.serviceChanged(Felix.java:625)
> at
> org.apache.felix.framework.ServiceRegistry.unregisterService(ServiceRegistry.java:117)
> at
> org.apache.felix.framework.ServiceRegistrationImpl.unregister(ServiceRegistrationImpl.java:128)
> at org.apache.felix.dm.test.RaceTest$AFactory$2.run(RaceTest.java:151)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:662)
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