[jboss-jira] [JBoss JIRA] Updated: (JBAS-4090) Race condition in Connection.close() can deadlock the JBossMQ's ping thread.

[Adrian Brock (JIRA)]

     [ http://jira.jboss.com/jira/browse/JBAS-4090?page=all ]

Adrian Brock updated JBAS-4090:
-------------------------------

    Attachment: patch.txt

> Race condition in Connection.close() can deadlock the JBossMQ's ping thread.
> ----------------------------------------------------------------------------
>
>                 Key: JBAS-4090
>                 URL: http://jira.jboss.com/jira/browse/JBAS-4090
>             Project: JBoss Application Server
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>          Components: JMS service
>    Affects Versions: JBossAS-5.0.0.Beta1, JBossAS-4.0.5.GA, JBossAS-3.2.8.SP1
>            Reporter: Adrian Brock
>         Assigned To: Adrian Brock
>             Fix For: JBossAS-4.0.5.SP1 , JBossAS-5.0.0.Beta2, JBossAS-4.2.0.CR1
>
>         Attachments: patch.txt
>
>
> There is a race condition between the JBossMQ ping thread and connection.close()
> that can cause the ping thread to become deadlocked.
> Besides meaning that the ping stops working so broken connections are not detected,
> this can also evenutally lead to a memory leak.
> The problem occurs when the connection.close()
> requests to cancel the ping for that connection, and then aquires the semaphore
> to make sure the ping has stopped working.
> Just at that moment, the ping was scheduled to run and tries to aquire the semaphore
> (with no timeout), but it never can because the connection.close() has permenantly
> aquired it.
> The obvious fix is to include a timeout in the ping task such that when it fails
> to acquire the semaphore it can assume that the connection was closed and return
> immediately.
> Additionally, checking the "closing" flag should also avoid even trying to acquire
> the semaphore when the connection is being closed (in most cases).

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