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From "Jonathan Ellis (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-6557) CommitLogSegment may be duplicated in unlikely race scenario
Date Fri, 17 Jan 2014 12:39:19 GMT


Jonathan Ellis commented on CASSANDRA-6557:

bq. The alternative, of course, is to lock when we want to aAF. 

Let's do that for now then.

bq. it doesn't absolutely need NBQ, so if we want to avoid adding it for now, we can

You have correctly divined my motivation. :)

> CommitLogSegment may be duplicated in unlikely race scenario
> ------------------------------------------------------------
>                 Key: CASSANDRA-6557
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: 2.1
>            Reporter: Benedict
>             Fix For: 2.1
> In the unlikely event that the thread that switched to a new CLS has not finished executing
the cleanup of its switch by the time the CLS has finished being used, it is possible for
the same segment to be 'switched' in again. This would be benign except that it is added to
the activeSegments queue a second time also, which would permit it to be recycled twice, creating
two different CLS objects in memory pointing to the same CLS on disk, after which all bets
are off.
> The issue is highly unlikely to occur, but highly unlikely means it will probably happen
eventually. I've fixed this based on my patch for CASSANDRA-5549, using the NonBlockingQueue
I introduce there to simplify the logic and make it more obviously correct.

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