[jira] Updated: (JCR-2000) Deadlock on concurrent commits

["Jukka Zitting (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/JCR-2000?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jukka Zitting updated JCR-2000:
-------------------------------

    Attachment: JCR-2000.patch

Attached a patch that solves the issue for environments where the transaction manager does not use separate threads for preparing and committing a transaction (see JCR-1334). Support for JCR-1334 requires updating also the version manager lock to support switching the lock ownership from one thread to another.

> Deadlock on concurrent commits
> ------------------------------
>
>                 Key: JCR-2000
>                 URL: https://issues.apache.org/jira/browse/JCR-2000
>             Project: Jackrabbit Content Repository
>          Issue Type: Bug
>          Components: jackrabbit-core, transactions
>    Affects Versions: 1.5.3
>            Reporter: Jukka Zitting
>            Assignee: Jukka Zitting
>             Fix For: 1.5.4
>
>         Attachments: JCR-2000.patch
>
>
> As reported in the followup to JCR-1979, there's a case where two transactions may be concurrently inside a commit. This is bad as it breaks the main assumption in http://jackrabbit.apache.org/concurrency-control.html about all transactions first acquiring the versioning write lock.
> Looking deeper into this I find that the versioning write lock is only acquired if the transaction being committed contains versioning operations. This is incorrect as all transactions in any case need to access the version store when checking for references.

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