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From "Felix Meschberger (JIRA)" <j...@apache.org>
Subject [jira] Updated: (FELIX-490) Deadlocks may be caused by Declarative Services
Date Thu, 14 Feb 2008 10:11:09 GMT

     [ https://issues.apache.org/jira/browse/FELIX-490?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Felix Meschberger updated FELIX-490:

    Attachment: threaddump.txt

Thread dump showing this deadlock. This dump has been attached to SLING-245.

> Deadlocks may be caused by Declarative Services
> -----------------------------------------------
>                 Key: FELIX-490
>                 URL: https://issues.apache.org/jira/browse/FELIX-490
>             Project: Felix
>          Issue Type: Bug
>          Components: Declarative Services
>    Affects Versions: 1.0.0
>            Reporter: Felix Meschberger
>         Attachments: threaddump.txt
> The Declarative Services implementation has an AbstractComponentManager class which implementa
the lifecycles of components in methods like enable, activate, deactivate, disable and dispose.
All methods come in two flavors an (private) internal on which is synchronized and executes
the action and a public unsynchronized one calling the internal one on a separate thread.
> All internal methods are generally called only from the separate thread so are guaranteed
to run sequentially on after the other due to the queing in the thread. One exception is the
deactivate method which is always called directly and not in the separate thread. So a component
may be deactivated while it is actually being activated. This is why the internal methods
are synchronized - to delay a deactivation in case an activation already active.
> The problem is, that activate calls in to the framework to get at services or to register
services. At the same time the deactivate method may be called from within the framework for
example because a required or static dependency has been unregistered. This may now create
a deadlock between the activate method trying to register a service and the service unregistration
trying to call the deactivate method.
> The fix is to look at a more finegrained synchronization mechanism in the AbstractComponentManager.
> Similar behaviour is reported in FELIX-489, which is currently analysed looking from
the framework to the outside.

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