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https://issues.apache.org/jira/browse/SSHD-721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16438468#comment-16438468
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Bill Kuker commented on SSHD-721:
---------------------------------
[~johnnyv] That is correct. I do not think switching over to an unbounded
thread pool is the right solution, but it is a temporary workaround for the bug
for me.
If whichever operation is blocking could be converted to non-blocking that
could fix the issue, or running these 2 different kinds of operation in 2
different thread pools could also fix the issue.
> deadlock: all nio workers wait to be woken up
> ---------------------------------------------
>
> Key: SSHD-721
> URL: https://issues.apache.org/jira/browse/SSHD-721
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 1.3.0, 1.4.0
> Reporter: Markus Rathgeb
> Priority: Major
>
> I am using sshd-core for a server machine (S) that accepts incoming
> connections and port forwarding requests.
> There are client machines (C) that run servers that should be accessible by a
> tunnel to the server.
> On the client machines (C) also an implementation using sshd-core is running
> that establish the connection to the server (S) and initiate the port
> forwarding.
> Other clients are using the tunnelled connection to communicate with the
> servers that are running on the client machines (C).
> Sometimes I realized that no data is transferred anymore (through the
> tunnels).
> All the worker reside in the waitFor function and no one wakes them up.
> {noformat}
> "sshd-SshServer[67de991c]-nio2-thread-3" - Thread t@125
> java.lang.Thread.State: TIMED_WAITING
> at java.lang.Object.wait(Native Method)
> - waiting on <132c6b60> (a java.lang.Object)
> at
> org.apache.sshd.client.channel.AbstractClientChannel.waitFor(AbstractClientChannel.java:244)
> at
> org.apache.sshd.common.forward.DefaultTcpipForwarder$StaticIoHandler.messageReceived(DefaultTcpipForwarder.java:984)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.handleReadCycleCompletion(Nio2Session.java:276)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$1.onCompleted(Nio2Session.java:256)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$1.onCompleted(Nio2Session.java:253)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.lambda$completed$0(Nio2CompletionHandler.java:38)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$$Lambda$45/1071326492.run(Unknown
> Source)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:37)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker$2.run(Invoker.java:218)
> at
> sun.nio.ch.AsynchronousChannelGroupImpl$1.run(AsynchronousChannelGroupImpl.java:112)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> at java.lang.Thread.run(Thread.java:745)
> Locked ownable synchronizers:
> - locked <6d02d7ed> (a java.util.concurrent.ThreadPoolExecutor$Worker)
> "sshd-SshServer[67de991c]-nio2-thread-2" - Thread t@124
> java.lang.Thread.State: TIMED_WAITING
> at java.lang.Object.wait(Native Method)
> - waiting on <7e9f4eff> (a java.lang.Object)
> at
> org.apache.sshd.client.channel.AbstractClientChannel.waitFor(AbstractClientChannel.java:244)
> at
> org.apache.sshd.common.forward.DefaultTcpipForwarder$StaticIoHandler.messageReceived(DefaultTcpipForwarder.java:984)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.handleReadCycleCompletion(Nio2Session.java:276)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$1.onCompleted(Nio2Session.java:256)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$1.onCompleted(Nio2Session.java:253)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.lambda$completed$0(Nio2CompletionHandler.java:38)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$$Lambda$45/1071326492.run(Unknown
> Source)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:37)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker$2.run(Invoker.java:218)
> at
> sun.nio.ch.AsynchronousChannelGroupImpl$1.run(AsynchronousChannelGroupImpl.java:112)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> at java.lang.Thread.run(Thread.java:745)
> Locked ownable synchronizers:
> - locked <35fbf3e8> (a java.util.concurrent.ThreadPoolExecutor$Worker)
> "sshd-SshServer[67de991c]-nio2-thread-1" - Thread t@122
> java.lang.Thread.State: TIMED_WAITING
> at java.lang.Object.wait(Native Method)
> - waiting on <49ce93a9> (a java.lang.Object)
> at
> org.apache.sshd.client.channel.AbstractClientChannel.waitFor(AbstractClientChannel.java:244)
> at
> org.apache.sshd.common.forward.DefaultTcpipForwarder$StaticIoHandler.messageReceived(DefaultTcpipForwarder.java:984)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.handleReadCycleCompletion(Nio2Session.java:276)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$1.onCompleted(Nio2Session.java:256)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$1.onCompleted(Nio2Session.java:253)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.lambda$completed$0(Nio2CompletionHandler.java:38)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$$Lambda$45/1071326492.run(Unknown
> Source)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:37)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:304)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:249)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.startReading(Nio2Session.java:243)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.startReading(Nio2Session.java:239)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.startReading(Nio2Session.java:235)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.startReading(Nio2Session.java:231)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.startReading(Nio2Session.java:227)
> at
> org.apache.sshd.common.io.nio2.Nio2Acceptor$AcceptCompletionHandler.onCompleted(Nio2Acceptor.java:178)
> at
> org.apache.sshd.common.io.nio2.Nio2Acceptor$AcceptCompletionHandler.onCompleted(Nio2Acceptor.java:156)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.lambda$completed$0(Nio2CompletionHandler.java:38)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$$Lambda$45/1071326492.run(Unknown
> Source)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:37)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker$2.run(Invoker.java:218)
> at
> sun.nio.ch.AsynchronousChannelGroupImpl$1.run(AsynchronousChannelGroupImpl.java:112)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> at java.lang.Thread.run(Thread.java:745)
> Locked ownable synchronizers:
> - locked <7d1c59e6> (a java.util.concurrent.ThreadPoolExecutor$Worker)
> "sshd-SshServer[67de991c]-timer-thread-1" - Thread t@105
> java.lang.Thread.State: TIMED_WAITING
> at sun.misc.Unsafe.park(Native Method)
> - parking to wait for <655c080c> (a
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
> at
> java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1093)
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)
> at
> java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> at java.lang.Thread.run(Thread.java:745)
> Locked ownable synchronizers:
> - None
> {noformat}
> To eliminate some other code that could trigger that error I created a
> "minimal" example -- a simple test application -- that could be used to
> demonstrate the hang (for me it is reproducible using that code).
> Please have a look at
> https://github.com/maggu2810/sshd-deadlock/tree/first-report where you could
> also find a readme with a short description about the code.
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