Deadlock in Timeout

I have encountered a deadlock with connection timeouts. It appears two locks are being acquired by the two threads in opposite order, which leads to a classic deadlock.

This deadlock is intermittent, and I am unable to make a consistent test case. It looks like the SelectChannelConnector$ConnectorEndPoint.blockWritable() method is attempting to scheduleIdle a TimeoutTask the same time the Acceptor1 thread is expiring that task (called from Timeout.tick()).

I've attached the thread dumps below.

Regards,
Stephen

Thread Dumps:

"831453930@qtp-211225614-8 - Acceptor1 SelectChannelConnector@0.0.0.0:8080" - Thread t@25
java.lang.Thread.State: BLOCKED on org.mortbay.jetty.nio.SelectChannelConnector$ConnectorEndPoint@5f35a7a1 owned by: 1835465145@qtp-211225614-7
at org.mortbay.io.nio.SelectChannelEndPoint.updateKey(SelectChannelEndPoint.java:322)
at org.mortbay.io.nio.SelectChannelEndPoint.close(SelectChannelEndPoint.java:456)
at org.mortbay.jetty.nio.SelectChannelConnector$ConnectorEndPoint.close(SelectChannelConnector.java:362)
at org.mortbay.io.nio.SelectChannelEndPoint.idleExpired(SelectChannelEndPoint.java:174)
at org.mortbay.io.nio.SelectChannelEndPoint$IdleTask.expire(SelectChannelEndPoint.java:489)
at org.mortbay.thread.Timeout.tick(Timeout.java:137)

• locked org.mortbay.io.nio.SelectorManager$SelectSet@229e90f9
  at org.mortbay.thread.Timeout.tick(Timeout.java:153)
  at org.mortbay.io.nio.SelectorManager$SelectSet.doSelect(SelectorManager.java:762)
  at org.mortbay.io.nio.SelectorManager.doSelect(SelectorManager.java:192)
  at org.mortbay.jetty.nio.SelectChannelConnector.accept(SelectChannelConnector.java:124)
  at org.mortbay.jetty.AbstractConnector$Acceptor.run(AbstractConnector.java:708)
  at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

Locked ownable synchronizers:

• None

"1835465145@qtp-211225614-7" - Thread t@24
java.lang.Thread.State: BLOCKED on org.mortbay.io.nio.SelectorManager$SelectSet@229e90f9 owned by: 831453930@qtp-211225614-8 - Acceptor1 SelectChannelConnector@0.0.0.0:8080
at org.mortbay.io.nio.SelectorManager$SelectSet.scheduleIdle(SelectorManager.java:797)
at org.mortbay.io.nio.SelectChannelEndPoint.scheduleIdle(SelectChannelEndPoint.java:159)
at org.mortbay.io.nio.SelectChannelEndPoint.blockWritable(SelectChannelEndPoint.java:293)

• locked org.mortbay.jetty.nio.SelectChannelConnector$ConnectorEndPoint@5f35a7a1
  at org.mortbay.jetty.AbstractGenerator$Output.blockForOutput(AbstractGenerator.java:544)
  at org.mortbay.jetty.AbstractGenerator$Output.flush(AbstractGenerator.java:571)
  at org.mortbay.jetty.HttpConnection$Output.flush(HttpConnection.java:1010)
  at sun.nio.cs.StreamEncoder.implFlush(StreamEncoder.java:278)
  at sun.nio.cs.StreamEncoder.flush(StreamEncoder.java:122)
• locked java.io.OutputStreamWriter@67770a61
  at java.io.OutputStreamWriter.flush(OutputStreamWriter.java:212)
  at java.io.PrintWriter.flush(PrintWriter.java:276)
• locked java.io.OutputStreamWriter@67770a61
  ... (snip)
  at javax.servlet.http.HttpServlet.service(HttpServlet.java:616)
  at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
  at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
  at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
  ... (snip)
  at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
  at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
  at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
  at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
  at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
  at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:440)
  at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
  at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
  at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
  at org.mortbay.jetty.Server.handle(Server.java:326)
  at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
  at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:943)
  at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:756)
  at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
  at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
  at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
  at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

Locked ownable synchronizers:

• None