Found one Java-level deadlock:
=============================
"Ruby Thread3208181":
  waiting for ownable synchronizer 0x1a3e9170, (a java.util.concurrent.locks.ReentrantLock$NonfairSync),
  which is held by "Ruby Thread10333950"
"Ruby Thread10333950":
  waiting to lock monitor 0x0180be98 (object 0x1a3fc468, a org.jruby.internal.runtime.ThreadService),
  which is held by "Ruby Thread3208181"

Java stack information for the threads listed above:
===================================================
"Ruby Thread3208181":
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x1a3e9170> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:158)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:712)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:743)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1079)
        at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:186)
        at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:262)
        at org.jruby.internal.runtime.ThreadService.setCritical(ThreadService.java:171)
        - locked <0x1a3fc468> (a org.jruby.internal.runtime.ThreadService)
        at org.jruby.RubyThread.critical_set(RubyThread.java:454)
        at org.jruby.RubyThreadInvoker$critical_set_FS1.call(Unknown Source)
        at org.jruby.runtime.callback.FastInvocationCallback.execute(FastInvocationCallback.java:49)
        at org.jruby.internal.runtime.methods.SimpleCallbackMethod.call(SimpleCallbackMethod.java:70)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.runtime.Dispatcher$DefaultDispatcher.callMethod(Dispatcher.java:15)
        at org.jruby.RubyObject.callMethod(RubyObject.java:509)
        at org.jruby.RubyObject.compilerCallMethodWithIndex(RubyObject.java:537)
        at org.jruby.javasupport.util.CompilerHelpers.doAttrAssignIndexed(CompilerHelpers.java:117)
        at mon_enter11152166_13485723.__file__(/Users/niko/projects/jruby.svn/lib/ruby/1.8/monitor.rb:210)
        at mon_enter11152166_13485723.run(/Users/niko/projects/jruby.svn/lib/ruby/1.8/monitor.rb)
        at org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:124)
        at org.jruby.evaluator.EvaluationState.vcallNode(EvaluationState.java:1749)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:381)
        at org.jruby.evaluator.EvaluationState.blockNode(EvaluationState.java:534)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:200)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:138)
        at org.jruby.internal.runtime.methods.AliasMethod.call(AliasMethod.java:60)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.evaluator.EvaluationState.fCallNode(EvaluationState.java:1034)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:252)
        at org.jruby.evaluator.EvaluationState.blockNode(EvaluationState.java:534)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:200)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:138)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.evaluator.EvaluationState.fCallNode(EvaluationState.java:1034)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:252)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:138)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.evaluator.EvaluationState.fCallNode(EvaluationState.java:1034)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:252)
        at org.jruby.evaluator.EvaluationState.blockNode(EvaluationState.java:534)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:200)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:138)
        at org.jruby.evaluator.EvaluationState.fCallNode(EvaluationState.java:1027)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:252)
        at org.jruby.evaluator.EvaluationState.blockNode(EvaluationState.java:534)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:200)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.runtime.Block.yield(Block.java:217)
        at org.jruby.runtime.Block.call(Block.java:170)
        at org.jruby.RubyProc.call(RubyProc.java:174)
        at org.jruby.RubyProc.call(RubyProc.java:154)
        at org.jruby.RubyProcInvoker$call_opt.call(Unknown Source)
        at org.jruby.runtime.callback.InvocationCallback.execute(InvocationCallback.java:58)
        at org.jruby.internal.runtime.methods.FullFunctionCallbackMethod.call(FullFunctionCallbackMethod.java:73)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.runtime.Dispatcher$DefaultDispatcher.callMethod(Dispatcher.java:15)
        at org.jruby.RubyObject.callMethod(RubyObject.java:509)
        at org.jruby.evaluator.EvaluationState.callNode(EvaluationState.java:564)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:206)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:138)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.runtime.Dispatcher$DefaultDispatcher.callMethod(Dispatcher.java:15)
        at org.jruby.RubyObject.callMethod(RubyObject.java:509)
        at org.jruby.evaluator.EvaluationState.callNode(EvaluationState.java:564)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:206)
        at org.jruby.evaluator.EvaluationState.rescueNode(EvaluationState.java:1506)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:349)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.runtime.Block.yield(Block.java:217)
        at org.jruby.runtime.Block.call(Block.java:170)
        at org.jruby.RubyProc.call(RubyProc.java:174)
        at org.jruby.RubyProc.call(RubyProc.java:149)
        at org.jruby.internal.runtime.RubyNativeThread.run(RubyNativeThread.java:73)
"Ruby Thread10333950":
        at org.jruby.internal.runtime.ThreadService.setCritical(ThreadService.java:162)
        - waiting to lock <0x1a3fc468> (a org.jruby.internal.runtime.ThreadService)
        at org.jruby.RubyThread.critical_set(RubyThread.java:454)
        at org.jruby.RubyThreadInvoker$critical_set_FS1.call(Unknown Source)
        at org.jruby.runtime.callback.FastInvocationCallback.execute(FastInvocationCallback.java:49)
        at org.jruby.internal.runtime.methods.SimpleCallbackMethod.call(SimpleCallbackMethod.java:70)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.runtime.Dispatcher$DefaultDispatcher.callMethod(Dispatcher.java:15)
        at org.jruby.RubyObject.callMethod(RubyObject.java:509)
        at org.jruby.RubyObject.compilerCallMethodWithIndex(RubyObject.java:537)
        at org.jruby.javasupport.util.CompilerHelpers.doAttrAssignIndexed(CompilerHelpers.java:117)
        at mon_enter11152166_13485723.__file__(/Users/niko/projects/jruby.svn/lib/ruby/1.8/monitor.rb:213)
        at mon_enter11152166_13485723.run(/Users/niko/projects/jruby.svn/lib/ruby/1.8/monitor.rb)
        at org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:124)
        at org.jruby.evaluator.EvaluationState.vcallNode(EvaluationState.java:1749)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:381)
        at org.jruby.evaluator.EvaluationState.blockNode(EvaluationState.java:534)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:200)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:138)
        at org.jruby.internal.runtime.methods.AliasMethod.call(AliasMethod.java:60)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.evaluator.EvaluationState.fCallNode(EvaluationState.java:1034)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:252)
        at org.jruby.evaluator.EvaluationState.blockNode(EvaluationState.java:534)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:200)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:138)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.evaluator.EvaluationState.fCallNode(EvaluationState.java:1034)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:252)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:138)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.evaluator.EvaluationState.fCallNode(EvaluationState.java:1034)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:252)
        at org.jruby.evaluator.EvaluationState.blockNode(EvaluationState.java:534)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:200)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:138)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.evaluator.EvaluationState.fCallNode(EvaluationState.java:1034)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:252)
        at org.jruby.evaluator.EvaluationState.blockNode(EvaluationState.java:534)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:200)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.runtime.Block.yield(Block.java:217)
        at org.jruby.runtime.Block.call(Block.java:170)
        at org.jruby.RubyProc.call(RubyProc.java:174)
        at org.jruby.RubyProc.call(RubyProc.java:154)
        at org.jruby.RubyProcInvoker$call_opt.call(Unknown Source)
        at org.jruby.runtime.callback.InvocationCallback.execute(InvocationCallback.java:58)
        at org.jruby.internal.runtime.methods.FullFunctionCallbackMethod.call(FullFunctionCallbackMethod.java:73)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.runtime.Dispatcher$DefaultDispatcher.callMethod(Dispatcher.java:15)
        at org.jruby.RubyObject.callMethod(RubyObject.java:509)
        at org.jruby.evaluator.EvaluationState.callNode(EvaluationState.java:564)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:206)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:138)
        at org.jruby.RubyObject.callMethod(RubyObject.java:526)
        at org.jruby.runtime.Dispatcher$DefaultDispatcher.callMethod(Dispatcher.java:15)
        at org.jruby.RubyObject.callMethod(RubyObject.java:509)
        at org.jruby.evaluator.EvaluationState.callNode(EvaluationState.java:564)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:206)
        at org.jruby.evaluator.EvaluationState.rescueNode(EvaluationState.java:1506)
        at org.jruby.evaluator.EvaluationState.evalInternal(EvaluationState.java:349)
        at org.jruby.evaluator.EvaluationState.eval(EvaluationState.java:163)
        at org.jruby.runtime.Block.yield(Block.java:217)
        at org.jruby.runtime.Block.call(Block.java:170)
        at org.jruby.RubyProc.call(RubyProc.java:174)
        at org.jruby.RubyProc.call(RubyProc.java:149)
        at org.jruby.internal.runtime.RubyNativeThread.run(RubyNativeThread.java:73)

Found 1 deadlock.