[jboss-jira] [JBoss JIRA] Commented: (JGRP-1103) NakReceiverWindow: concurrent insertion may insert the same seqno multiple times

[Bela Ban (JIRA)]

    [ https://jira.jboss.org/jira/browse/JGRP-1103?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12495867#action_12495867 ] 

Bela Ban commented on JGRP-1103:
--------------------------------

When the code which was moved outside the lock scope was moved back, NakReceiverWindowTest2 passed every single time ! This confirms my assumption regarding the cause of the bug...

> NakReceiverWindow: concurrent insertion may insert the same seqno multiple times
> --------------------------------------------------------------------------------
>
>                 Key: JGRP-1103
>                 URL: https://jira.jboss.org/jira/browse/JGRP-1103
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>            Priority: Blocker
>             Fix For: 2.8
>
>
> When concurrently inserting the same range of seqnos (e.g. 1-100) into the NakReceiverWindow by N threads (e.g. 10), we sometimes end up with duplicate messages for the *same* seqno ! This happens very rarely and only when many threads insert the same message !
> This can be observed in DuplicateTest (testOOBMulticastsToAll3Senders()): sometimes the final list contains more than 10 elements.
> I reproduced this by testing NakReceiverWindow in isolation, the test is NakReceiverWindowTest2.
> I assume this is a regression introduced in 2.8 by moving insertions to and removal from xmit_table out of the write_lock scope in method NakReceiverWindow.add().

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