[jira] Commented: (LUCENE-1347) IndexWriter.rollback can hang if a previous call hit an exception

["Yonik Seeley (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-1347?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12618356#action_12618356 ] 

Yonik Seeley commented on LUCENE-1347:
--------------------------------------

Looks good Mike!
Just one question.... it looks like there might be a race condition in rollbackInternal()
Thread A calls rollbackInternal calls closeInternal which executes the finally block, waking up thread B.
Thread B sets closing=true and then calls closeInternal or rollbackInternal... meanwhile thread A executes the finally block in rollbackInternal and sets closing=false (oops, it shouldn't do that if closeInternal already did it).

That breaks the invariant, and thread C could then set closing=true and call closeInternal or rollbackInternal concurrently with thread B.

Not sure if this would cause any real problems or not though.


> IndexWriter.rollback can hang if a previous call hit an exception
> -----------------------------------------------------------------
>
>                 Key: LUCENE-1347
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1347
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Index
>    Affects Versions: 2.3, 2.3.1
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>            Priority: Minor
>             Fix For: 2.3.2, 2.4
>
>         Attachments: LUCENE-1347.patch
>
>
> IW.rollback has logic to make sure only one thread actually gets to do
> the rollback whenever multiple threads are calling it at the same
> time, by setting the "boolean closing" to true in the thread that got
> there first.
> Other threads wait for that variable to become false again before
> returning from abort.
> But, we are not restoring closing to false in a try/finally in
> rollback(), which means on hitting an exception in rollback, a
> subsequent call to rollback() will hang forever.
> close() has the same logic, but there is already a try/finally there
> to restore closing to false on exception.
> The fix is straightforward.

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