[jira] [Commented] (OAK-4532) race-condition in commit-rate-limiter

["Stefan Egli (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-4532?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15361489#comment-15361489 ] 

Stefan Egli commented on OAK-4532:
----------------------------------

/cc [~mduerig]

> race-condition in commit-rate-limiter
> -------------------------------------
>
>                 Key: OAK-4532
>                 URL: https://issues.apache.org/jira/browse/OAK-4532
>             Project: Jackrabbit Oak
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.5.4
>            Reporter: Stefan Egli
>
> [CommitRateLimiter.delay|https://github.com/apache/jackrabbit-oak/blob/jackrabbit-oak-1.5.4/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/observation/CommitRateLimiter.java#L81] has a race-condition when the queue length drops below thres-hold right when {{delay()}} is called. Consider the following steps:
> * thread T1 enters {{delay()}} with a positive value for {{delay}} but gets paused right after the check for {{delay>0}}
> * thread T2 enters {{setDelay(0)}}, thus goes into the synchronized block and does a notifyAll
> * thread T1 continues in {{delay()}} after above mentioned check, thus now goes into the synchronized block - at this stage {{delay}} is {{0}} (as it's volatile) - thus it sets {{dt=0}}.
> * thread T1 then goes and calls {{wait(0)}} - which is an infinite wait, until it gets notified. This can be forever if the threshold is never ever hit again.
> Would suggest to do a {{while}} loop rather than a {{do-while}}



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