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From "Philippe Mouawad (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LOGGING-119) deadlock on re-registration of logger
Date Mon, 15 Sep 2008 11:31:45 GMT

    [ https://issues.apache.org/jira/browse/LOGGING-119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12630999#action_12630999
] 

Philippe Mouawad commented on LOGGING-119:
------------------------------------------

The bug is due to 2 different ways of taking locks :

Purge or purgeOne:
1) locks queue
2) lock this through super.remove

Put the calls super.put()
1) lock this through super.put()
2) call to rehash in super.put()
3) rehash calls purge (which locks queue) => YOU GOT THE DEAD LOCK

The solution is to call super#remove in purge and purgeOne outside of the synchronized (queue)
lock.



> deadlock on re-registration of logger
> -------------------------------------
>
>                 Key: LOGGING-119
>                 URL: https://issues.apache.org/jira/browse/LOGGING-119
>             Project: Commons Logging
>          Issue Type: Bug
>    Affects Versions: 1.1.1
>         Environment: Java 1.5, Windows
>            Reporter: Nitzan Niv
>         Attachments: BugDeadlock.java, Patch-WeakHashtable-1.1.1.txt
>
>
> Reached a deadlock inside common-logging while concurrently re-deploying 2 WARs.
> In each WAR there is an attempt to get a logger:
> private final Log logger = LogFactory.getLog(ContextLoader.class);
> Thread dump:
> [deadlocked thread] Thread-96:
> -----------------------------
> Thread 'Thread-96' is waiting to acquire lock 'java.lang.ref.ReferenceQueue@5266e0' that
is held by thread 'Thread-102'
> Stack trace:
> ------------
>         org.apache.commons.logging.impl.WeakHashtable.purge(WeakHashtable.java:323)
>         org.apache.commons.logging.impl.WeakHashtable.rehash(WeakHashtable.java:312)
>         java.util.Hashtable.put(Hashtable.java:414)
>         org.apache.commons.logging.impl.WeakHashtable.put(WeakHashtable.java:242)
>         org.apache.commons.logging.LogFactory.cacheFactory(LogFactory.java:1004)
>         org.apache.commons.logging.LogFactory.getFactory(LogFactory.java:657)
>         org.apache.commons.logging.LogFactory.getLog(LogFactory.java:685)
>         org.springframework.web.context.ContextLoader.<init>(ContextLoader.java:145)
>  
> [deadlocked thread] Thread-102:
> ------------------------------
> Thread 'Thread-102' is waiting to acquire lock 'org.apache.commons.logging.impl.
> WeakHashtable@1e02138' that is held by thread 'Thread-96'
> Stack trace:
> ------------
>         java.util.Hashtable.remove(Hashtable.java:437)
>         org.apache.commons.logging.impl.WeakHashtable.purgeOne(WeakHashtable.java:338)
>         org.apache.commons.logging.impl.WeakHashtable.put(WeakHashtable.java:238)
>         org.apache.commons.logging.LogFactory.cacheFactory(LogFactory.java:1004)
>         org.apache.commons.logging.LogFactory.getFactory(LogFactory.java:657)
>         org.apache.commons.logging.LogFactory.getLog(LogFactory.java:685)
>         org.springframework.web.context.ContextLoader.<init>(ContextLoader.java:145)

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