[jboss-jira] [JBoss JIRA] Commented: (JGRP-933) NAKACK/UNICAST: eager lock releasing not respected

[Bela Ban (JIRA)]

    [ https://jira.jboss.org/jira/browse/JGRP-933?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12458007#action_12458007 ] 

Bela Ban commented on JGRP-933:
-------------------------------

Might have to deprecate eager_lock_release. This doesn't make any sense anyway with atomic boolean vars, because there's ever only 1 thread from the same sender removing messages. So the following scenario

- Thread1 is acquiring the lock for sender S
- Thread2 is waiting to acquire the lock for sender S
- Thread1 removes message M1 and passes it up
- Thread1 is used to send a message, so down() is invoked and the lock for sender S is released if eager_lock_release is true
- Thread2 can remove the next message while Thread1 is still sending a message down

cannot happen, because Thread2 will CAS the atomic boolean and return if the CAS fails !

> NAKACK/UNICAST: eager lock releasing not respected
> --------------------------------------------------
>
>                 Key: JGRP-933
>                 URL: https://jira.jboss.org/jira/browse/JGRP-933
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 2.9
>
>
> In both NAKACK and UNICAST, we have atomic booleans, which are consulted before trying to acquire the lock. So if a lock is released eagerly in a ProtocolStack.down() call, although the lock is released, the atomic var isn't, and so subsequent threads will still not be able to process different messages.
> A simple solution would be to release the lock *and* the atomic var in down().
> OTOH, we should see whether we can use either locks or atomic vars, but not *both*.
> This will need to be redesigned anyway with scopes in place (https://jira.jboss.org/jira/browse/JGRP-822).

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