This has happen a few times. Apparently the "Free Disk Space"-monitoring thread can cause a job to freeze so bad that it cannot be aborted in anyway.

You can do the following without being able to abort the job:

• Cancel the job through the Web UI
• Disconnect/reconnect the slave running the job
• Do a hard reboot on the slave running the job
• Delete the slave from Hudson.

Regardless if the slave is deleted, the job will be shown as running in Hudson (and the slave will still be visible in the executors list)

The only way to unfreeze the job is to restart Hudson.

More so, the freeze seems to generate a pretty bad thread leak/build up.

Now, to the details (I'm sorry, but I can not post a full thread stack atm):

The Free Disk Space-job that caused the lock on the remote channel:

"Monitoring thread for Free Disk Space started on Wed Feb 24 17:33:12 CET 2010" prio=10 tid=0x3d623400 nid=0x2020 runnable [0x402eb000]
java.lang.Thread.State: RUNNABLE
at java.io.FileOutputStream.writeBytes(Native Method)
at java.io.FileOutputStream.write(FileOutputStream.java:260)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:65)
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:123)

• locked <0x5d1cd630> (a java.io.BufferedOutputStream)
  at java.io.ObjectOutputStream$BlockDataOutputStream.flush(ObjectOutputStream.java:1784)
  at java.io.ObjectOutputStream.flush(ObjectOutputStream.java:691)
  at hudson.remoting.Channel.send(Channel.java:418)
• locked <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Request.call(Request.java:149)
• locked <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.FilePath.act(FilePath.java:683)
  at hudson.FilePath.act(FilePath.java:676)
  at hudson.node_monitors.DiskSpaceMonitor$1.getFreeSpace(DiskSpaceMonitor.java:71)
  at hudson.node_monitors.DiskSpaceMonitorDescriptor.monitor(DiskSpaceMonitorDescriptor.java:135)
  at hudson.node_monitors.DiskSpaceMonitorDescriptor.monitor(DiskSpaceMonitorDescriptor.java:49)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200

It has now been stuck at the writeBytes()-method for about 20h.

The stuck job:

"Handling GET /view/XXXXXXX/job/HANGED_JOB/descriptorByName/CheckStylePublisher/checkPattern : http-8080-1" daemon prio=10 tid=0x0839d000 nid=0x1549 waiting for monitor entry [0x431fd000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.FilePath.act(FilePath.java:683)
  at hudson.FilePath.act(FilePath.java:676)
  at hudson.FilePath.exists(FilePath.java:944)
  at hudson.util.FormFieldValidator$WorkspaceFileMask.check(FormFieldValidator.java:377)
  at hudson.util.FormFieldValidator.process(FormFieldValidator.java:140)
  at hudson.plugins.checkstyle.util.PluginDescriptor.doCheckPattern(PluginDescriptor.java:93)
  at sun.reflect.GeneratedMethodAccessor685.invoke(Unknown Source)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  at java.lang.reflect.Method.invoke(Method.java:597)
  at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:169)
  at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:101)
  at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:54)
  at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:74)
  at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
  at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:180)
  at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
  at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:180)
  at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
  at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:180)
  at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:435)
  at org.kohsuke.stapler.Stapler.service(Stapler.java:123)
  at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:94)
  at hudson.plugins.greenballs.GreenBallFilter.doFilter(GreenBallFilter.java:51)
  at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:97)
  at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:86)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
  at hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:166)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at org.acegisecurity.ui.basicauth.BasicProcessingFilter.doFilter(BasicProcessingFilter.java:173)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
  at hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:66)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
  at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
  at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
  at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433)
  at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
  at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
  at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
  at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
  at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
  at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
  at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
  at java.lang.Thread.run(Thread.java:619)

"Executor #0 for lnx0391 : executing HANGED_JOB #197" prio=10 tid=0x465f6000 nid=0x15b3 waiting for monitor entry [0x40ad4000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:148)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.FilePath.act(FilePath.java:683)
  at hudson.FilePath.act(FilePath.java:676)
  at hudson.plugins.checkstyle.CheckStylePublisher.perform(CheckStylePublisher.java:99)
  at hudson.plugins.checkstyle.util.HealthAwarePublisher.perform(HealthAwarePublisher.java:136)
  at hudson.tasks.BuildStepMonitor$3.perform(BuildStepMonitor.java:36)
  at hudson.model.AbstractBuild$AbstractRunner.perform(AbstractBuild.java:582)
  at hudson.model.AbstractBuild$AbstractRunner.performAllBuildStep(AbstractBuild.java:563)
  at hudson.model.AbstractBuild$AbstractRunner.performAllBuildStep(AbstractBuild.java:550)
  at hudson.model.Build$RunnerImpl.post2(Build.java:152)
  at hudson.model.AbstractBuild$AbstractRunner.post(AbstractBuild.java:528)
  at hudson.model.Run.run(Run.java:1221)
  at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
  at hudson.model.ResourceController.execute(ResourceController.java:88)
  at hudson.model.Executor.run(Executor.java:122)

And the rest of the locked threads (building up each time Hudson tries to collect info from the slaves):

"pool-3-thread-532" daemon prio=10 tid=0x43592000 nid=0x3668 waiting for monitor entry [0x3a0e8000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Channel.close(Channel.java:720)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.slaves.SlaveComputer.closeChannel(SlaveComputer.java:450)
  at hudson.slaves.SlaveComputer.access$800(SlaveComputer.java:74)
  at hudson.slaves.SlaveComputer$4.run(SlaveComputer.java:390)
  at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
  at java.util.concurrent.FutureTask.run(FutureTask.java:138)
  at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
  at java.lang.Thread.run(Thread.java:619)

"Monitoring thread for Clock Difference started on Thu Feb 25 08:33:12 CET 2010" prio=10 tid=0x08172800 nid=0x35be waiting for monitor entry [0x39ff5000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.model.Slave.getClockDifference(Slave.java:230)
  at hudson.node_monitors.ClockMonitor$1.monitor(ClockMonitor.java:53)
  at hudson.node_monitors.ClockMonitor$1.monitor(ClockMonitor.java:49)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Architecture started on Thu Feb 25 08:33:12 CET 2010" prio=10 tid=0x08bdd000 nid=0x35bd waiting for monitor entry [0x3a046000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.node_monitors.ArchitectureMonitor$DescriptorImpl.monitor(ArchitectureMonitor.java:44)
  at hudson.node_monitors.ArchitectureMonitor$DescriptorImpl.monitor(ArchitectureMonitor.java:41)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Free Temp Space started on Thu Feb 25 08:33:12 CET 2010" prio=10 tid=0x08c01000 nid=0x35bc waiting for monitor entry [0x3a097000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.FilePath.act(FilePath.java:683)
  at hudson.FilePath.act(FilePath.java:676)
  at hudson.node_monitors.TemporarySpaceMonitor$1.getFreeSpace(TemporarySpaceMonitor.java:73)
  at hudson.node_monitors.DiskSpaceMonitorDescriptor.monitor(DiskSpaceMonitorDescriptor.java:135)
  at hudson.node_monitors.DiskSpaceMonitorDescriptor.monitor(DiskSpaceMonitorDescriptor.java:49)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Free Disk Space started on Thu Feb 25 08:33:12 CET 2010" prio=10 tid=0x08bfb000 nid=0x35bb waiting for monitor entry [0x3a1f9000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.FilePath.act(FilePath.java:683)
  at hudson.FilePath.act(FilePath.java:676)
  at hudson.node_monitors.DiskSpaceMonitor$1.getFreeSpace(DiskSpaceMonitor.java:71)
  at hudson.node_monitors.DiskSpaceMonitorDescriptor.monitor(DiskSpaceMonitorDescriptor.java:135)
  at hudson.node_monitors.DiskSpaceMonitorDescriptor.monitor(DiskSpaceMonitorDescriptor.java:49)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Free Swap Space started on Thu Feb 25 08:33:12 CET 2010" prio=10 tid=0x08bda400 nid=0x35ba waiting for monitor entry [0x3a1a8000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.node_monitors.SwapSpaceMonitor$1.monitor(SwapSpaceMonitor.java:83)
  at hudson.node_monitors.SwapSpaceMonitor$1.monitor(SwapSpaceMonitor.java:81)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Response Time started on Thu Feb 25 08:33:12 CET 2010" prio=10 tid=0x08de0c00 nid=0x35b8 waiting for monitor entry [0x3a430000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Channel.send(Channel.java:411)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Request.callAsync(Request.java:170)
  at hudson.remoting.Channel.callAsync(Channel.java:578)
  at hudson.node_monitors.ResponseTimeMonitor$1.monitor(ResponseTimeMonitor.java:58)
  at hudson.node_monitors.ResponseTimeMonitor$1.monitor(ResponseTimeMonitor.java:52)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Clock Difference started on Thu Feb 25 07:33:12 CET 2010" prio=10 tid=0x091fe400 nid=0x33eb waiting for monitor entry [0x3a24a000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.model.Slave.getClockDifference(Slave.java:230)
  at hudson.node_monitors.ClockMonitor$1.monitor(ClockMonitor.java:53)
  at hudson.node_monitors.ClockMonitor$1.monitor(ClockMonitor.java:49)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Architecture started on Thu Feb 25 07:33:12 CET 2010" prio=10 tid=0x08663c00 nid=0x33ea waiting for monitor entry [0x4695c000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.node_monitors.ArchitectureMonitor$DescriptorImpl.monitor(ArchitectureMonitor.java:44)
  at hudson.node_monitors.ArchitectureMonitor$DescriptorImpl.monitor(ArchitectureMonitor.java:41)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Free Temp Space started on Thu Feb 25 07:33:12 CET 2010" prio=10 tid=0x08de3800 nid=0x33e9 waiting for monitor entry [0x469ad000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.FilePath.act(FilePath.java:683)
  at hudson.FilePath.act(FilePath.java:676)
  at hudson.node_monitors.TemporarySpaceMonitor$1.getFreeSpace(TemporarySpaceMonitor.java:73)
  at hudson.node_monitors.DiskSpaceMonitorDescriptor.monitor(DiskSpaceMonitorDescriptor.java:135)
  at hudson.node_monitors.DiskSpaceMonitorDescriptor.monitor(DiskSpaceMonitorDescriptor.java:49)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Free Disk Space started on Thu Feb 25 07:33:12 CET 2010" prio=10 tid=0x083dec00 nid=0x33e8 waiting for monitor entry [0x469fe000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.FilePath.act(FilePath.java:683)
  at hudson.FilePath.act(FilePath.java:676)
  at hudson.node_monitors.DiskSpaceMonitor$1.getFreeSpace(DiskSpaceMonitor.java:71)
  at hudson.node_monitors.DiskSpaceMonitorDescriptor.monitor(DiskSpaceMonitorDescriptor.java:135)
  at hudson.node_monitors.DiskSpaceMonitorDescriptor.monitor(DiskSpaceMonitorDescriptor.java:49)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Free Swap Space started on Thu Feb 25 07:33:12 CET 2010" prio=10 tid=0x0815f800 nid=0x33e7 waiting for monitor entry [0x3b8c1000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.node_monitors.SwapSpaceMonitor$1.monitor(SwapSpaceMonitor.java:83)
  at hudson.node_monitors.SwapSpaceMonitor$1.monitor(SwapSpaceMonitor.java:81)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Response Time started on Thu Feb 25 07:33:12 CET 2010" prio=10 tid=0x082ba800 nid=0x33e5 waiting for monitor entry [0x3b402000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Channel.send(Channel.java:411)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Request.callAsync(Request.java:170)
  at hudson.remoting.Channel.callAsync(Channel.java:578)
  at hudson.node_monitors.ResponseTimeMonitor$1.monitor(ResponseTimeMonitor.java:58)
  at hudson.node_monitors.ResponseTimeMonitor$1.monitor(ResponseTimeMonitor.java:52)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Clock Difference started on Thu Feb 25 06:33:12 CET 2010" prio=10 tid=0x0890b800 nid=0x32f8 waiting for monitor entry [0x3a29b000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.model.Slave.getClockDifference(Slave.java:230)
  at hudson.node_monitors.ClockMonitor$1.monitor(ClockMonitor.java:53)
  at hudson.node_monitors.ClockMonitor$1.monitor(ClockMonitor.java:49)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

"Monitoring thread for Architecture started on Thu Feb 25 06:33:12 CET 2010" prio=10 tid=0x0865a000 nid=0x32f7 waiting for monitor entry [0x3a3df000]
java.lang.Thread.State: BLOCKED (on object monitor)
at hudson.remoting.Request.call(Request.java:100)

• waiting to lock <0x5c7a8ef0> (a hudson.remoting.Channel)
  at hudson.remoting.Channel.call(Channel.java:551)
  at hudson.node_monitors.ArchitectureMonitor$DescriptorImpl.monitor(ArchitectureMonitor.java:44)
  at hudson.node_monitors.ArchitectureMonitor$DescriptorImpl.monitor(ArchitectureMonitor.java:41)
  at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:200)

+ Another 80 (or so) other locked threads.