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https://issues.apache.org/jira/browse/FELIX-6616?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tom Watson closed FELIX-6616.
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> Dynamic greedy 1..1 references may activate with no reference service bound
> ---------------------------------------------------------------------------
>
> Key: FELIX-6616
> URL: https://issues.apache.org/jira/browse/FELIX-6616
> Project: Felix
> Issue Type: Bug
> Components: Declarative Services (SCR)
> Affects Versions: scr-2.2.6
> Reporter: Tom Watson
> Assignee: Tom Watson
> Priority: Major
> Fix For: scr-2.2.8, scr-2.2.10
>
>
> If using a 1..1 cardinality for a dynamic greedy reference there is a timing
> issue possible which will cause SCR to unbind all reference when activating
> the component.
> The timing window involves at least two threads.
> 1) thread 1 is in the process of activating the component with a 1..1 dynamic
> greedy reference to service X (ranking=1)
> 2) thread 2 is in the process of registering another service X with a higher
> service ranking=100
> When this happens thread 1 determines it should bind service X ranking 1.
> Thread 1 creates the service component instance and enables the tracking of
> all the dependencies. It then proceeds to bind all the required services.
> Before binding service X ranking=1 thread 2 registers service X ranking=100.
> Thread 2 then finds the created service component instance that thread 1 has
> created (but is still in the process of binding all the services) and then
> thread 2 binds service X ranking=100. At this point thread 2 thinks the
> component actually got bound to service X ranking=1 so it begins to unbind
> it. Before unbinding, if thread 1 proceeds it will bind service X ranking=1.
> So now the component itself (depending on the implementation) will start
> using X ranking=1. But then thread 2 proceeds and it will unbind service X
> ranking=1.
> So basically we are left with this flow:
> 1) bind X ranking=100
> 2) bind X ranking=1
> 3) unbind X ranking =1
> At this point the component will be confused and think it likely has no
> services to use.
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