Deadlock between AbstractWorkingMemory and DefaultAgenda

I experienced a deadlock when running in STREAM mode and using negative patterns with temporal constraints.
When the rule gets fired by the installed timer job and at the same time another thread is firing rules, a deadlock can occur:

1. [rule firing thread] StatefulKnowledgeSessionImpl.execute(StatefulKnowledgeSessionImpl.java:820)
acquires lock in AbstractWorkingMemory

2. [timer-thread] DefaultAgenda.fireActivation()
call of synchronized method

3. [rule firing thread] DefaultAgenda.fireActivation()
synchronized method, wait for other thread to exit synchornized method

4. [timer-thread] AbstractWorkingMemory.getGlobal()
tries to access a global, tries to acquire lock in AbstractWorkingMemory which is held by the other thread

--> Deadlock

Excerpt from thread dump:

"http-thread-pool-8082(374)":
at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1264)

• waiting to lock <0x00007f50407e4950> (a org.drools.common.DefaultAgenda)
  at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1221)
  at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1456)
  at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:710)
  at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:679)
  at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:234)
  at org.drools.command.runtime.rule.FireAllRulesCommand.execute(FireAllRulesCommand.java:102)
  at org.drools.command.runtime.rule.FireAllRulesCommand.execute(FireAllRulesCommand.java:32)
  at org.drools.command.runtime.BatchExecutionCommandImpl.execute(BatchExecutionCommandImpl.java:155)
  at org.drools.command.runtime.BatchExecutionCommandImpl.execute(BatchExecutionCommandImpl.java:76)
  at org.drools.impl.StatefulKnowledgeSessionImpl.execute(StatefulKnowledgeSessionImpl.java:821)

"pool-4251-thread-1":
at sun.misc.Unsafe.park(Native Method)

• parking to wait for 0x00007f503fc71a20> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
  at java.util.concurrent.locks.LockSupport.park(LockSupport.java:158)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:747)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:778)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1114)
  at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:186)
  at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:262)
  at org.drools.common.AbstractWorkingMemory.getGlobal(AbstractWorkingMemory.java:634)
  at myrules.Rule_ruleWithTimeout_ece4a3c9fc2741a4ab97a92b77611203DefaultConsequenceInvokerGenerated.evaluate(Unknown Source)
  at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1287)
• locked <0x00007f50407e4950> (a org.drools.common.DefaultAgenda)
  at org.drools.common.DefaultAgenda.fireTimedActivation(DefaultAgenda.java:1344)
• locked <0x00007f50407e4950> (a org.drools.common.DefaultAgenda)
  at org.drools.common.Scheduler$ActivationTimerJob.execute(Scheduler.java:83)