[jira] [Updated] (SLING-11620) Synchronization issue in Webconsole Security Provider

["Carsten Ziegeler (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SLING-11620?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Carsten Ziegeler updated SLING-11620:
-------------------------------------
    Fix Version/s: Web Console Security Provider 1.2.8

> Synchronization issue in Webconsole Security Provider
> -----------------------------------------------------
>
>                 Key: SLING-11620
>                 URL: https://issues.apache.org/jira/browse/SLING-11620
>             Project: Sling
>          Issue Type: Bug
>          Components: Extensions
>    Affects Versions: Web Console Security Provider 1.2.6
>            Reporter: Sagar Miglani
>            Assignee: Carsten Ziegeler
>            Priority: Major
>             Fix For: Web Console Security Provider 1.2.8
>
>         Attachments: BlockedThreads.png, SLING-11620_fix.patch, WebconsoleServiceListeners.patch
>
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> WebconsoleSecurityProvider's [ServiceListeners|https://github.com/apache/sling-org-apache-sling-extensions-webconsolesecurityprovider/blob/master/src/main/java/org/apache/sling/extensions/webconsolesecurityprovider/internal/ServicesListener.java] class has three fields of Listener (an inner class of {{ServiceListeners}} implementing {{{}ServiceListener{}}}) {{{}repositoryListener{}}}, {{{}authSupportListener{}}}, {{{}authListener{}}}.
> Each of listener uses synchronized methods and on any {{ServiceChanged}} event it may call {{notifyChange}} method of {{ServiceListeners}} outer class which is also a synchronized method and in this method we are again calling all of the listener fields' {{getService}} sychronized methods
> If two service events for these listeneres fields occur simulatenously a deadlock situation may arise.
> eg:
> Thread1:
>  - repositoryListener -> serviceChanged
>  - synchronized retainSerivce - (self lock acquired)
>  - synchronized notifyChange - (outer class' lock acquired)
> Thread2:
>  - authSupportListener -> serviceChanged
>  - synchronized retainService - (self lock aquired)
>  - synchronized notifyChange - (wait for thread 1 to release outer class' lock)
> Thread1:
>  - synchronized (authSupportListener) getService - (wait for thread 2 to release the lock)
> Tried to replicate the scenario [^WebconsoleServiceListeners.patch]. The test in this patch file fails due to timeout.
> On taking thread snapshot you may see the thread blocked and waiting for each other. [^BlockedThreads.png]
> Shouldn't these all listener fields and outer class be using the shared lock instead of sychronized methods?



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