[jboss-jira] [JBoss JIRA] Updated: (JBCACHE-794) Eviction Queue hard limit can cause deadlocks

[Manik Surtani (JIRA)]

     [ http://jira.jboss.com/jira/browse/JBCACHE-794?page=all ]

Manik Surtani updated JBCACHE-794:
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    JBoss Forum Reference: http://jboss.org/index.html?module=bb&op=viewtopic&p=3979697
               Complexity: High

> Eviction Queue hard limit can cause deadlocks
> ---------------------------------------------
>
>                 Key: JBCACHE-794
>                 URL: http://jira.jboss.com/jira/browse/JBCACHE-794
>             Project: JBoss Cache
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>    Affects Versions: 1.4.0.SP1
>            Reporter: Owen Taylor
>         Assigned To: Manik Surtani
>             Fix For: 1.4.0.SP2, 2.0.0
>
>
> if the eviction queue fills up, you can get the situation where:
>  - The eviction queue processing task calls evict() which needs to get a write lock on a node
>  - A different thread has a read lock on that node and is blocking to put something into the eviction queue
> Once this starts happening the evication queue thread is procesing events *very* slowly because
> it repeatedly stalls while the lock times out, so the queue will stay full.
> Without digging into the code too much, possible fixes that occur to me include:
>  1) Don't have a hard limit on the size of the eviction queue, and just warn when it gets too big
>  2) Use a timeout of 0 when trying to get the write lock to evict a node, after all, if a node is
>       locked when we try to evict it, it probably shouldn't be evicted anyways.

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