Deadlock on LeftTupleSets

Java stack information for the threads listed above:
===================================================
"drools-worker-2":
        at org.drools.core.common.DefaultAgenda.addEagerRuleAgendaItem(DefaultAgenda.java:282)
        - waiting to lock <0x00000007d8fc80d0> (a java.util.LinkedList)
        at org.drools.core.reteoo.PathMemory.queueRuleAgendaItem(PathMemory.java:153)
        at org.drools.core.reteoo.PathMemory.doLinkRule(PathMemory.java:120)
        - locked <0x00000007d91f34d0> (a org.drools.core.reteoo.PathMemory)
        at org.drools.core.reteoo.PathMemory.linkSegment(PathMemory.java:90)
        at org.drools.core.reteoo.SegmentMemory.notifyRuleLinkSegment(SegmentMemory.java:170)
        at org.drools.core.reteoo.LeftInputAdapterNode$LiaNodeMemory.setNodeDirty(LeftInputAdapterNode.java:645)
        at org.drools.core.reteoo.LeftInputAdapterNode.doUpdateSegmentMemory(LeftInputAdapterNode.java:396)
        - locked <0x00000007d91f68a8> (a java.lang.Object)
        at org.drools.core.reteoo.LeftInputAdapterNode.doUpdateObject(LeftInputAdapterNode.java:366)
        at org.drools.core.reteoo.LeftInputAdapterNode.modifyObject(LeftInputAdapterNode.java:436)
        at org.drools.core.reteoo.CompositeObjectSinkAdapter.doPropagateModifyObject(CompositeObjectSinkAdapter.java:512)
        at org.drools.core.reteoo.CompositeObjectSinkAdapter.propagateModifyObject(CompositeObjectSinkAdapter.java:437)
        at org.drools.core.reteoo.ObjectTypeNode.modifyObject(ObjectTypeNode.java:382)
        at org.drools.core.reteoo.EntryPointNode.modifyObject(EntryPointNode.java:273)
        at org.drools.core.common.NamedEntryPoint.update(NamedEntryPoint.java:511)
        at org.drools.core.base.DefaultKnowledgeHelper.update(DefaultKnowledgeHelper.java:385)
        at drools.core.Rule_vme$u46$phases_inconnues1199361134.defaultConsequence(Rule_vme$u46$phases_inconnues1199361134.java:19)
        at drools.core.Rule_vme$u46$phases_inconnues1199361134DefaultConsequenceInvokerGenerated.evaluate(Unknown Source)
        at drools.core.Rule_vme$u46$phases_inconnues1199361134DefaultConsequenceInvoker.evaluate(Unknown Source)
        at org.drools.core.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1046)
        - locked <0x00000007d8fc8080> (a org.drools.core.common.DefaultAgenda)
        at org.drools.core.phreak.RuleExecutor.fire(RuleExecutor.java:152)
        at org.drools.core.phreak.RuleExecutor.fire(RuleExecutor.java:100)
        - locked <0x00000007d9335498> (a org.drools.core.phreak.RuleExecutor)
        at org.drools.core.phreak.PhreakTimerNode$Executor.evauateAndFireRule(PhreakTimerNode.java:483)
        at org.drools.core.phreak.PhreakTimerNode$TimerNodeJob$1.run(PhreakTimerNode.java:420)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:744)
"Drools thread":
        at org.drools.core.common.SynchronizedLeftTupleSets.takeAll(SynchronizedLeftTupleSets.java:44)
        - waiting to lock <0x00000007d91f68a8> (a java.lang.Object)
        at org.drools.core.phreak.RuleNetworkEvaluator.evaluateNetwork(RuleNetworkEvaluator.java:112)
        at org.drools.core.phreak.RuleExecutor.evaluateNetwork(RuleExecutor.java:77)
        - locked <0x00000007d9334c40> (a org.drools.core.phreak.RuleExecutor)
        at org.drools.core.common.DefaultAgenda.evaluateEagerList(DefaultAgenda.java:990)
        - locked <0x00000007d8fc80d0> (a java.util.LinkedList)
        at org.drools.core.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:945)
        at org.drools.core.common.DefaultAgenda.fireUntilHalt(DefaultAgenda.java:1190)
        at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireUntilHalt(StatefulKnowledgeSessionImpl.java:1329)
        at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireUntilHalt(StatefulKnowledgeSessionImpl.java:1306)
        at drools.core.Core$2.run(Core.java:495)
        at java.lang.Thread.run(Thread.java:744)