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https://issues.jenkins-ci.org/browse/JENKINS-5413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=161636#comment-161636
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Christian Wolfgang commented on JENKINS-5413:
---------------------------------------------
We have solved our problems now.
It turned out, that the underlying framework for the plugin threw
RuntimeExceptions which were not catched all the time. After we handled those
exceptions the slaves stopped hanging.
> SCM polling on slaves getting hung
> ----------------------------------
>
> Key: JENKINS-5413
> URL: https://issues.jenkins-ci.org/browse/JENKINS-5413
> Project: Jenkins
> Issue Type: Bug
> Components: master-slave
> Affects Versions: current
> Reporter: Dean Yu
> Attachments: hung_scm_pollers_02.PNG, threads.vetted.txt,
> thread_dump_02.txt
>
>
> This is to track the problem originally reported here:
> http://n4.nabble.com/Polling-hung-td1310838.html#a1310838
> The referenced thread is relocated to
> http://jenkins.361315.n4.nabble.com/Polling-hung-td1310838.html
> What the problem boils down to is that many remote operations are performed
> synchronously causing the channel object to be locked while a response
> returns. In situations where a lengthy remote operations is using the
> channel, SCM polling can be blocked waiting for the monitor on the channel to
> be released. In extreme situations, all the polling threads can wind up
> waiting on object monitors for the channel objects, preventing further
> processing of polling tasks.
> Furthermore, if the slave dies, the locked channel object still exists in the
> master JVM. If no IOException is thrown to indicate the termination of the
> connection to the pipe, the channel can never be closed because
> Channel.close() itself is a sychronized operation.
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