[jira] [Commented] (QPID-8554) [Broker-J] Infinite loop in CachingSecurityToken class

["Alex Rudyy (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/QPID-8554?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17402861#comment-17402861 ] 

Alex Rudyy commented on QPID-8554:
----------------------------------

Hi [~lacam],
Could you please provide more details on conditions when the reported issue manifest?

IMHO, the loop should eventually ends after the updating the CACHE_UPDATE.

> [Broker-J] Infinite loop in CachingSecurityToken class
> ------------------------------------------------------
>
>                 Key: QPID-8554
>                 URL: https://issues.apache.org/jira/browse/QPID-8554
>             Project: Qpid
>          Issue Type: Bug
>          Components: Broker-J
>            Reporter: Marek Laca
>            Priority: Minor
>              Labels: Broker, Java, thread-safe
>
> The CachingSecurityToken class is caching the authorization results. It can be utilized by multiple threads at the same time. Hence, it has to be multi-thread safe. The CachingSecurityToken::authorise could get stuck in an infinite loop when multiple threads try to update the local cache simultaneously.
> Two threads can be in permanent conflict when each thread is trying to override changes of another thread.
> {code:java}
> AccessControlCache cache;
> while((cache = CACHE_UPDATE.get(this)).getAccessControl() != ruleBasedAccessControl)
> {
>     CACHE_UPDATE.compareAndSet(this, cache, new AccessControlCache(ruleBasedAccessControl));
> }
> {code}



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