Deadlock trying to synchronize 'eager' field in DefaultAgenda (drools-worker thread and the other thread) --------------------------------------------------------------------------------------------------------- Key: DROOLS-776 URL: https://issues.jboss.org/browse/DROOLS-776 Project: Drools Issue Type: Feature Request Affects Versions: 6.2.0.Final Reporter: Juan Carlos Garcia Assignee: Mark Proctor Migrating from drools 6.0.1.Final to 6.2.0.Final there seems to be a rare deadlock trying to syncronized the DefaultAgenda *eager* field, i have seen it only 2 or three times now as it seems very dificult to reproduce. In our scenario the test is calling *kSession.fireUntilHalt()* in a new thread, then in the main thread waiting for some events to happens (by calling in a loop: kSession.getObjects(new ClassObjectFilter(_clazz)))) and then doing some other assert checks. See the stacktrace below i took with jstack: {code} Java stack information for the threads listed above: =================================================== "Thread-5": at org.drools.core.phreak.RuleExecutor.evaluateNetwork(RuleExecutor.java:92) - waiting to lock <0x00000000ff245780> (a org.drools.core.phreak.RuleExecutor) at org.drools.core.common.DefaultAgenda.evaluateEagerList(DefaultAgenda.java:1044) - locked <0x00000000ff3dab38> (a org.drools.core.util.LinkedList) at org.drools.core.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:996) at org.drools.core.common.DefaultAgenda.fireUntilHalt(DefaultAgenda.java:1258) at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireUntilHalt(StatefulKnowledgeSessionImpl.java:1333) at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireUntilHalt(StatefulKnowledgeSessionImpl.java:1310) at bar.foo.AIDelayTest$1.run(AIDelayTest.java:101) at java.lang.Thread.run(Thread.java:745) "drools-worker-2": at org.drools.core.common.DefaultAgenda.addEagerRuleAgendaItem(DefaultAgenda.java:287) - waiting to lock <0x00000000ff3dab38> (a org.drools.core.util.LinkedList) at org.drools.core.reteoo.PathMemory.queueRuleAgendaItem(PathMemory.java:159) at org.drools.core.reteoo.PathMemory.doUnlinkRule(PathMemory.java:133) - locked <0x00000000ff2457a0> (a org.drools.core.reteoo.PathMemory) at org.drools.core.reteoo.PathMemory.unlinkedSegment(PathMemory.java:173) at org.drools.core.reteoo.SegmentMemory.unlinkNode(SegmentMemory.java:203) at org.drools.core.reteoo.BetaMemory.unlinkNode(BetaMemory.java:100) at org.drools.core.reteoo.BetaNode.doDeleteRightTuple(BetaNode.java:377) at org.drools.core.reteoo.JoinNode.retractRightTuple(JoinNode.java:107) at org.drools.core.reteoo.ObjectTypeNode.doRetractObject(ObjectTypeNode.java:345) at org.drools.core.reteoo.ObjectTypeNode.retractObject(ObjectTypeNode.java:337) at org.drools.core.reteoo.EntryPointNode.retractObject(EntryPointNode.java:381) at org.drools.core.common.NamedEntryPoint.delete(NamedEntryPoint.java:615) at org.drools.core.base.DefaultKnowledgeHelper.delete(DefaultKnowledgeHelper.java:495) at org.drools.core.base.DefaultKnowledgeHelper.retract(DefaultKnowledgeHelper.java:486) at bar.foo.Rule_basic$u46$delayExecution$u46$01246876731.defaultConsequence(Rule_basic$u46$delayExecution$u46$01246876731.java:7) at bar.foo.Rule_basic$u46$delayExecution$u46$01246876731DefaultConsequenceInvokerGenerated.evaluate(Unknown Source) at bar.foo.Rule_basic$u46$delayExecution$u46$01246876731DefaultConsequenceInvoker.evaluate(Unknown Source) at org.drools.core.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1114) - locked <0x00000000ff3da978> (a org.drools.core.common.DefaultAgenda) at org.drools.core.phreak.RuleExecutor.fire(RuleExecutor.java:160) at org.drools.core.phreak.RuleExecutor.fire(RuleExecutor.java:112) - locked <0x00000000ff245780> (a org.drools.core.phreak.RuleExecutor) at org.drools.core.phreak.PhreakTimerNode$Executor.qevauateAndFireRule(PhreakTimerNode.java:485) at org.drools.core.phreak.PhreakTimerNode$TimerNodeJob$1.run(PhreakTimerNode.java:420) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Found 1 deadlock. {code}