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https://issues.apache.org/jira/browse/FELIX-3456?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Jencks updated FELIX-3456:
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Attachment: FELIX-3456-7a.diff
FELIX-3456-7.diff
I like most of your patch and appreciate your fixing the sync enable for
default-enabled components.
There are still a couple problems:
1. I'd like a fair reentrant lock, doug lea's original doesn't appear to be
fair. I tried to use the emory dcl backport-util-concurrent which does
implement a fair lock but AFAICT it would require exporting sun.misc from the
framework which I don't think is acceptable. So, I implemented something I
think will work where the java.util.concurrent reentrant lock is used if
available and if not doug lea's unfair lock.
2. There were some problems around state change and trying to activate while
binding services. Basically the solution to 3317 is no longer relevant and we
can simplify the code a bit more. The state change to Active has to happen
earlier before checking the dependency managers or you always get the component
created several times, registered, and then unregistered. We have enough
locking already :-)
> Component ignores required static service addition when in Activating state
> ---------------------------------------------------------------------------
>
> Key: FELIX-3456
> URL: https://issues.apache.org/jira/browse/FELIX-3456
> Project: Felix
> Issue Type: Bug
> Components: Declarative Services (SCR)
> Affects Versions: scr-1.6.0
> Environment: Using org.apache.felix.scr svn rev 1298268 on Mac
> Reporter: Richard Ellis
> Priority: Critical
> Attachments: FELIX-3456-1.1.diff, FELIX-3456-1.diff,
> FELIX-3456-3.diff, FELIX-3456-4.diff, FELIX-3456-5.diff, FELIX-3456-5a.diff,
> FELIX-3456-5b.diff, FELIX-3456-7.diff, FELIX-3456-7a.diff,
> FELIX-3456-fmeschbe-6.patch, FELIX-3456-fmeschbe.patch
>
>
> I have a component with two required static service references (A and B). In
> my scenario A and B are registered nearly simultaneously on different threads
> and this causes the DependencyManager to ignore the addition of one of these
> two services (B). This causes the component to remain unsatisfied and never
> activate, since the service that was ignored is not re-registered at any time
> and nothing subsequently causes the component to re-activate.
> This happens as follows:
> 12:30:59:317 Thread 1 - Registers Service B/257
> 12:30:59:320 Thread 2 - Registers Service A/258
> 12:30:59:320 Thread 2 - Dependency Manager: Adding Service A/258
> 12:30:59:321 Thread 2 - Dependency Manager: Service serviceA registered,
> activate component
> 12:30:59:321 Thread 2 - State transition : Unsatisfied -> Activating
> 12:30:59:321 Thread 2 - Activating component
> 12:30:59:321 Thread 1 - Dependency Manager: Adding Service B/257
> 12:30:59:321 Thread 2 - Dependency not satisfied: serviceB
> 12:30:59:321 Thread 1 - Dependency Manager: Added service serviceB is ignored
> for static reference <--- I believe we end up here because Thread 2 has moved
> the component from Unsatisfied to Activating and the reference is a static
> reference
> 12:30:59:321 Thread 2 - Not all dependencies satisified, cannot activate
> 12:30:59:321 Thread 2 - State transition : Activating -> Unsatisfied
> Because the addition of Service B has been ignored and serviceB is a required
> dependency my component then never activates even though my reqiured service
> is present.
> There is a comment in DependencyManager#serviceAdded method:
> // FELIX-1413: if the dependency is static and the component is
> // satisfied (active) added services are not considered until
> // the component is reactivated for other reasons.
> This suggests that the static service should only be ignored if the component
> is satisfied(active), which would be correct, but in this case the component
> is only activating (and will fail to activate because one of the two
> dependencies is not yet satisfied) and there is no check of state at this
> time.
> A simple fix would be to check the state of the component as well as if the
> service is static e.g.
> replace if ( m_dependencyMetadata.isStatic() )
> with if ( m_dependencyMetadata.isStatic() && m_componentManager.getState() ==
> AbstractComponentManager.STATE_ACTIVE )
> This is an easy fix, but I guess may leave a small window where a static
> reference could get replaced while a component was still activating if
> another instance of the same service was registered on a different thread.
> There are other fixes that could be done by synchronizing more around service
> additions.
> Is anyone willing to make this fix or does anyone have any thoughts about
> this issue?
> Thanks
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