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https://issues.apache.org/jira/browse/TAPESTRY-1571?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12507661
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Ben Sommerville commented on TAPESTRY-1571:
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FYI - I just discovered the other day that due to a JVM bug, this patch will
cause a deadlock when running under jdk 6u1. The JVM bug report is at
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6571733. Apparently it is
fixed under jdk 6u2 & jdk7 so it is not a big issue.
If tapestry has to work under jdk6u1 then changing the ConcurrentBarrier
read/write lock to "fair" mode will get rid of the deadlock.
> CheckForUpdatesFilter can cause deadlock
> ----------------------------------------
>
> Key: TAPESTRY-1571
> URL: https://issues.apache.org/jira/browse/TAPESTRY-1571
> Project: Tapestry
> Issue Type: Bug
> Components: tapestry-core
> Affects Versions: 5.0.5
> Reporter: Ben Sommerville
> Assignee: Howard M. Lewis Ship
> Fix For: 5.0.5
>
> Attachments: TAP-1571.patch
>
>
> CheckForUpdatesFilter will cause a deadlock in the following circumstances.
> 1) Initial request is received and processing starts (CheckForUpdatesFilter
> read lock obtained)
> 2) Request processing triggers another http request to the same application
> 3) Nested request is received
> 4) CheckForUpdatesFilter determines it is time to check for file updates
> 5) CheckForUpdatesFilter tries to obtain write lock
> 6) Deadlock: Nested request is blocked waiting for read lock held by parent
> request to be released.
> This is an unusual situation, generally I wouldn't try to to access a page
> via http whilst trying to process another request. However I ran across this
> problem whilst using a third party library (JasperReports) that referenced
> resources via http links.
> Although uncommon, I believe Tapestry should be able to handle this without
> deadlocking
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