Brian Moseley wrote:
Marcel Reutegger wrote:
what revision of jackrabbit are you using? according to the line
numbers in the thread dumps at least the SharedItemStateManager is not
up to date.
there was an issue with locking some time ago.
http://issues.apache.org/jira/browse/JCR-194
is that fix included in your build?
i remember that issue. it was fixed in r239410, according to jira. im
running r330363, tho :/
hmm, I had another look at the thread dumps and the problem is indeed
the ReentrantWriterPreferenceReadWriteLock as you indicated in your
first post.
3 threads need to be involved for the deadlock:
thread-1: stores modification and is notifying events listeners (SISM
holds read lock), one of the listener is the lock manager (lock manager
is held by thread-2)
thread-2: checks locks state of a node (holds lock manager), lock
manager attempts to acquire a read lock on the SISM. there is a request
for a write lock by thread-3 which has preference.
thread-3: attempts to store modification, wants to acquire a write lock
on the SISM. waits for thread-1.
and the circle is closed :-/
changing the preference to readers will solve this issue. but I'm not
sure if there will be side effects with this change.
I'll run some tests first before I commit the change.
He is my suggested change:
Index: SharedItemStateManager.java
===================================================================
--- SharedItemStateManager.java (revision 349402)
+++ SharedItemStateManager.java (working copy)
@@ -144,7 +144,14 @@
* Read-/Write-Lock to synchronize access on this item state manager.
*/
private final ReadWriteLock rwLock =
- new ReentrantWriterPreferenceReadWriteLock();
+ new ReentrantWriterPreferenceReadWriteLock() {
+ /**
+ * Use reader preference policy.
+ */
+ protected boolean allowReader() {
+ return true;
+ }
+ };
/**
* Creates a new <code>SharedItemStateManager</code> instance.
regards
marcel
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