Major Description
A deadlock issue happens when OpenJPA entity manager is
concurrently called and DirtyListener is used and
DirtyListener.beforeDirty calls an entity manager related
operation. To call OpenJPA entity manager concurrently,
we need to define openjpa.MulthThreaded option as true.
Following is test scenario.
1. Thread A calls entityMangaer.refresh() repeatedly.
In refresh() method, entityManager acquires BrokerImpl
lock. And then, entityManager acquires LifecycleEventManager
lock to call lifecycle callback.
2. Thread B calls persistedObject.getAItems() (getting
collection items).
3. In enhanced getItems() method, entityManager tries
to mark it as "dirty". Before marking, callback listener
DirtyListener.beforeDirty is called. In this point,
LifecycleEventManager lock is acquired without acquiring
BrokerImpl lock.
4. In the testcase, beforeDirty calls persistedObject.getAItems().
And then, entity manager tries to acquire BrokerImpl lock.
But, sometimes BrokerImpl lock is already acquired by Thread B.
So, a deadlock issue happens. deadlock stack is as follows.
====
[java] "Thread-1" prio=1 tid=0x09e98b28 nid=0x7fcc waiting on condition [0xb15f3000..0xb15f4130]
[java] at sun.misc.Unsafe.park(Native Method)
[java] at java.util.concurrent.locks.LockSupport.park(LockSupport.java:118)
[java] at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:716)
[java] at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:746)
[java] at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1076)
[java] at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:184)
[java] at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:256)
[java] at org.apache.openjpa.kernel.BrokerImpl.lock(BrokerImpl.java:4168)
[java] at org.apache.openjpa.kernel.BrokerImpl.beginOperation(BrokerImpl.java:1770)
[java] at org.apache.openjpa.kernel.BrokerImpl.isActive(BrokerImpl.java:1742)
[java] at org.apache.openjpa.kernel.StateManagerImpl.beforeRead(StateManagerImpl.java:964)
[java] at org.apache.openjpa.kernel.StateManagerImpl.accessingField(StateManagerImpl.java:1501)
[java] at model.A.getAItems(A.java)
[java] at model.ADirtyListener.beforeDirty(ADirtyListener.java:24)
[java] at org.apache.openjpa.event.LifecycleEventManager.fireEvent(LifecycleEventManager.java:423)
[java] at org.apache.openjpa.event.LifecycleEventManager.fireEvent(LifecycleEventManager.java:289)
[java] - locked <0x51b4e4b0> (a org.apache.openjpa.event.LifecycleEventManager)
[java] at org.apache.openjpa.kernel.BrokerImpl.fireLifecycleEvent(BrokerImpl.java:693)
[java] at org.apache.openjpa.kernel.StateManagerImpl.fireLifecycleEvent(StateManagerImpl.java:364)
[java] at org.apache.openjpa.kernel.StateManagerImpl.dirty(StateManagerImpl.java:1596)
[java] at org.apache.openjpa.kernel.StateManagerImpl.dirty(StateManagerImpl.java:1539)
[java] at org.apache.openjpa.util.Proxies.dirty(Proxies.java:66)
[java] at org.apache.openjpa.util.ProxyCollections.beforeAdd(ProxyCollections.java:57)
[java] at org.apache.openjpa.util.java$util$HashSet$proxy.add(Unknown Source)
[java] at business.Test$2.run(Test.java:80)
[java] at java.lang.Thread.run(Thread.java:595)
[java] "Thread-0" prio=1 tid=0x09e9d010 nid=0x7fcb waiting for monitor entry [0xb1674000..0xb1674db0]
[java] at org.apache.openjpa.event.LifecycleEventManager.fireEvent(LifecycleEventManager.java:272)
[java] - waiting to lock <0x51b4e4b0> (a org.apache.openjpa.event.LifecycleEventManager)
[java] at org.apache.openjpa.kernel.BrokerImpl.fireLifecycleEvent(BrokerImpl.java:693)
[java] at org.apache.openjpa.kernel.StateManagerImpl.fireLifecycleEvent(StateManagerImpl.java:364)
[java] at org.apache.openjpa.kernel.StateManagerImpl.clearFields(StateManagerImpl.java:2647)
[java] at org.apache.openjpa.kernel.StateManagerImpl.beforeRefresh(StateManagerImpl.java:1239)
[java] at org.apache.openjpa.kernel.BrokerImpl.refreshInternal(BrokerImpl.java:2835)
[java] at org.apache.openjpa.kernel.BrokerImpl.refresh(BrokerImpl.java:2781)
[java] at org.apache.openjpa.kernel.DelegatingBroker.refresh(DelegatingBroker.java:1078)
[java] at org.apache.openjpa.persistence.EntityManagerImpl.refresh(EntityManagerImpl.java:694)
[java] at business.Test$1.run(Test.java:64)
[java] at java.lang.Thread.run(Thread.java:595)
====
Intially the problem is reproduced on OpenJPA 1.x. But,
I verified the problem could be reproduced with latest
OpenJPA head.