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https://issues.apache.org/jira/browse/SSHD-721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16462632#comment-16462632
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Bill Kuker commented on SSHD-721:
---------------------------------
[~gnt] Thanks very much for your help, there is an issue with your patch. The
call to {{channel.getSession().exceptionCaught(e);}} is incorrect.
It causes the connection between the sshd server and ssh client to be closed
when an error occurs on the socket between the sshd server and the "web
browser," or whatever the application making the connection through the port
forward is.
I think there is a tough to make race condition, as that error has to occur on
the first, or an early, run through the new code when the open future is not
yet resolved. I am not familiar enough with the code to understand where the
exception would have gone when thrown from the synchronous version.
I have 100% confirmed that end users are not able to reliably use real web
browsers and real web servers under real world conditions *unless that line is
removed*. I am just not sure where, if anywhere, that exception should go if it
happens.
> 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
> Fix For: 2.0.0
>
>
> 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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