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https://issues.apache.org/jira/browse/JCR-2746?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12912864#action_12912864
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Thomas Mueller commented on JCR-2746:
-------------------------------------
The bug in DefaultISMLocking was introduces with JCR-2089 (Use
java.util.concurrent), revisions 995411 and 995412. I think the safe solution
is to revert those to commits. Test case:
public void test() throws InterruptedException {
final ISMLocking lock = new DefaultISMLocking();
ReadLock r1 = lock.acquireReadLock(null);
final InterruptedException[] ex = new InterruptedException[1];
Thread thread = new Thread() {
public void run() {
try {
lock.acquireWriteLock(null).release();
} catch (InterruptedException e) {
ex[0] = e;
}
}
};
thread.start();
Thread.sleep(100);
lock.acquireReadLock(null).release();
r1.release();
thread.join();
if (ex[0] != null) {
throw ex[0];
}
}
This will result in a deadlock with the current DefaultISMLocking, but not with
the old.
> Deadlock caused by ObservationDispatcher
> -----------------------------------------
>
> Key: JCR-2746
> URL: https://issues.apache.org/jira/browse/JCR-2746
> Project: Jackrabbit Content Repository
> Issue Type: Bug
> Components: jackrabbit-core, observation
> Affects Versions: 2.0.0, 2.1.0, 2.1.1
> Reporter: Jukka Zitting
> Assignee: Thomas Mueller
> Fix For: 2.2.0
>
>
> The rate-limitation code we added in JCR-2402 to prevent the observation
> queue from growing too large was a good idea, but the current implementation
> is a bit troublesome since it blocks the thread while it still holds the
> journal lock, the SISM reader lock, and the SessionState lock. This can cause
> a deadlock under heavy workloads if any of the observation listeners attempts
> to reuse the session (not recommended/supported, but can still happen) or
> write to the repository (quite likely).
> To solve this problem we should move the rate-limiter code to outside the
> scope of any internal locks.
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