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https://issues.apache.org/jira/browse/SSHD-721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16439365#comment-16439365
 ] 

Guillaume Nodet commented on SSHD-721:
--------------------------------------

[~bkuker1] thx, I'm waiting for the test so that I can then commit both...

Thread management could be improved on both the {{TcpipClientChannel}} and 
{{TcpipServerChannel}} by using the async streams ({{ChannelAsyncOutputStream}} 
instead of {{ChannelOutputStream}}).  This would avoid having threads waiting 
for available window space, packet being written, etc..  But that's only an 
improvement, and the current way should work too.  Feel free to raise a JIRA 
about using async stream though.

> 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
>            Assignee: Guillaume Nodet
>            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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