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

[Owen Taylor (JIRA)]

Eviction Queue hard limit can cause deadlocks
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                 Key: JBCACHE-794
                 URL: http://jira.jboss.com/jira/browse/JBCACHE-794
             Project: JBoss Cache
          Issue Type: Bug
      Security Level: Public (Everyone can see)
            Reporter: Owen Taylor
         Assigned To: Manik Surtani


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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