[
http://jira.jboss.com/jira/browse/JBCACHE-94?page=comments#action_12315987 ]
Bela Ban commented on JBCACHE-94:
---------------------------------
T0 is under tx to do removeObject("/aop", ...) of which has many sub-cache
operations. But first thing, it does a write on, say, /aop. Therefore, it put a
WL on /aop.
Meanwhile T1 comes in (also under another Tx) to do putObject("/aop",...). So
since T0 is not done, it somehow enter CreateNodeIfNoExist interceptor and
insert /aop fqn into put-list. But then it blocks since "/aop" is under WL.
Later on, T0 is trying to remove the node, but now it has to wait since /aop is
in the put-list.
So this is a deadlock. Eventually T1 will timeout and T0 proceeds.
Bela: this is documented in TxDeadlockUnitTestCase in
testCreateIfNotExistsLogic().
We will fix this for 1.2.1, but move to a different solution in 1.2.2
(LockTable) --> JBCACHE-107
> Incorrect synchronization between threads (CreateIfNotExistsInterceptor and
> LockInterceptor)
> --------------------------------------------------------------------------------------------
>
> Key: JBCACHE-94
> URL: http://jira.jboss.com/jira/browse/JBCACHE-94
> Project: JBoss Cache
> Type: Bug
> Reporter: Bela Ban
> Assignee: Bela Ban
> Priority: Blocker
> Fix For: 1.2.1
>
>
> Example (assumes RPE-READ (R/W lock) semantics):
> - TX1 does a put(/a/b/c)
> - TX1 acquires lock1 in CreateIfNotExistsInterceptor
> - TX1 creates /a/b (RL) and /a/b/c (WL), locking those nodes
> - TX2 does a put(/a/b/c/d), waits on CINE-Int
> - TX1 releases lock1
> - TX2 acquires lock1 and blocks on lock acquisition for /a/b/c (WL-ed by TX1)
> - TX1 does a remove(/a/b/c, key)
> - TX1 blocks on lock1 (held by TX2)
> - TX2 times out, rolls back changes and releases lock1
> - TX1 acquires lock1, makes the change, commits TX and releases all locks
> SOLUTION: we need to fine-grained synchronization in
> CreateIfNotExistsInterceptor
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