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https://issues.apache.org/jira/browse/ZOOKEEPER-1395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13239105#comment-13239105
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Henry Robinson commented on ZOOKEEPER-1395:
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+1 this looks sensible to me. I'll commit tonight or tomorrow.
> node-watcher double-free redux
> ------------------------------
>
> Key: ZOOKEEPER-1395
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1395
> Project: ZooKeeper
> Issue Type: Bug
> Components: c client, contrib-bindings
> Affects Versions: 3.3.4
> Reporter: Mike Lundy
> Assignee: Mike Lundy
> Priority: Critical
> Attachments: 3.3-0001-notify-on-event-state-not-current-state.patch,
> 3.[45]-0001-notify-on-event-state-not-current-state.patch
>
>
> This is basically the same issue as ZOOKEEPER-888 and ZOOKEEPER-740 (the
> latter is open as I write this, but it was superseded by the fix that went in
> with 888). The problem still exists after the ZOOKEEPER-888 patch, however;
> it's just more difficult to trigger:
> 1) Zookeeper notices connection loss, schedules watcher_dispatch
> 2) Zookeeper notices session loss, schedules watcher_dispatch
> 3) watcher_dispatch runs for connection loss
> 4) pywatcher is freed due to is_unrecoverable being true
> 5) watcher_dispatch runs for session loss
> 6) PyObject_CallObject attempts to run freed pywatcher with varying bad
> results
> The fix is easy, the dispatcher should act on the state it is given, not the
> state of the world when it runs. (Patch attached). Reliably triggering the
> crash is tricky due to the race, but it's not theoretical.
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