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Posted to dev@mina.apache.org by "ASF GitHub Bot (Jira)" <ji...@apache.org> on 2022/08/11 21:55:00 UTC
[jira] [Work logged] (SSHD-1289) Deadlock during session exit
[ https://issues.apache.org/jira/browse/SSHD-1289?focusedWorklogId=800119&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-800119 ]
ASF GitHub Bot logged work on SSHD-1289:
----------------------------------------
Author: ASF GitHub Bot
Created on: 11/Aug/22 21:54
Start Date: 11/Aug/22 21:54
Worklog Time Spent: 10m
Work Description: tomaswolf opened a new pull request, #238:
URL: https://github.com/apache/mina-sshd/pull/238
Make sure that a thread does not try to acquire the write lock if
it already holds the read lock. This could happen if a write is not
enqueued and there is an exception during writing, and we then try
to close the session on the same thread.
The read/write lock is used for three purposes: first, it gives the
flushing thread trying to empty the queue of pending packets priority
over other threads trying to enqueue more packets, and second, it is
held during writeOrEnqueue() while writing a packet directly to prevent
that the KEX state changes between being checked and the write being
done, and third, to prevent that the KEX state changes asynchronously
while the flushing thread is checking it. The read/write lock itself
does not serve to ensure mutual exclusion on the KEX state itself.
These three functions can also be fulfilled if update() is executed
when only the read lock is held. If a thread in update() holds the read
lock, this can only occur if it wrote the buffer directly in
writeOrEnqueue(), in which case it is fine to proceed, and the flushing
thread for sure is not in its critical region where it holds the write
lock. Otherwise, any other thread either is the flushing thread and
holds the write lock already, or it's a thread not holding the lock at
all. In both cases it is fine to acquire the write lock.
Issue Time Tracking
-------------------
Worklog Id: (was: 800119)
Remaining Estimate: 0h
Time Spent: 10m
> Deadlock during session exit
> ----------------------------
>
> Key: SSHD-1289
> URL: https://issues.apache.org/jira/browse/SSHD-1289
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 2.9.0
> Reporter: Evgeny Pasynkov
> Priority: Major
> Time Spent: 10m
> Remaining Estimate: 0h
>
> {code}
> java.lang.Thread.State: WAITING
> at java.base@11.0.5/jdk.internal.misc.Unsafe.park(Native Method)
> - waiting on java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync@c50d1b2
> at java.base@11.0.5/java.util.concurrent.locks.LockSupport.park(LockSupport.java:194)
> at java.base@11.0.5/java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:885)
> at java.base@11.0.5/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:917)
> at java.base@11.0.5/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1240)
> at java.base@11.0.5/java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.lock(ReentrantReadWriteLock.java:959)
> at org.apache.sshd.common.session.helpers.KeyExchangeMessageHandler.updateState(KeyExchangeMessageHandler.java:139)
> at org.apache.sshd.common.session.helpers.KeyExchangeMessageHandler.shutdown(KeyExchangeMessageHandler.java:186)
> at org.apache.sshd.common.session.helpers.AbstractSession.preClose(AbstractSession.java:967)
> at org.apache.sshd.common.util.closeable.AbstractCloseable.close(AbstractCloseable.java:94)
> at org.apache.sshd.common.session.helpers.AbstractSessionIoHandler.sessionClosed(AbstractSessionIoHandler.java:46)
> at org.apache.sshd.common.io.nio2.Nio2Session.doCloseImmediately(Nio2Session.java:283)
> at org.apache.sshd.common.util.closeable.AbstractCloseable.close(AbstractCloseable.java:95)
> at org.apache.sshd.common.io.nio2.Nio2Session.exceptionCaught(Nio2Session.java:215)
> at org.apache.sshd.common.io.nio2.Nio2Session.writeBuffer(Nio2Session.java:186)
> at org.apache.sshd.common.session.helpers.AbstractSession.doWritePacket(AbstractSession.java:1118)
> - locked java.lang.Object@3423f353
> at org.apache.sshd.common.session.helpers.KeyExchangeMessageHandler.writeOrEnqueue(KeyExchangeMessageHandler.java:285)
> at org.apache.sshd.common.session.helpers.KeyExchangeMessageHandler.writePacket(KeyExchangeMessageHandler.java:228)
> at org.apache.sshd.common.session.helpers.AbstractSession.writePacket(AbstractSession.java:1039)
> at org.apache.sshd.common.session.Session.writePacket(Session.java:159)
> at org.apache.sshd.common.session.Session.writePacket(Session.java:145)
> at org.apache.sshd.common.channel.AbstractChannel$GracefulChannelCloseable.close(AbstractChannel.java:637)
> at org.apache.sshd.common.util.closeable.SequentialCloseable$1.operationComplete(SequentialCloseable.java:56)
> at org.apache.sshd.common.util.closeable.SequentialCloseable$1.operationComplete(SequentialCloseable.java:45)
> at org.apache.sshd.common.util.closeable.SequentialCloseable.doClose(SequentialCloseable.java:69)
> at org.apache.sshd.common.util.closeable.SimpleCloseable.close(SimpleCloseable.java:63)
> at org.apache.sshd.common.util.closeable.SequentialCloseable$1.operationComplete(SequentialCloseable.java:56)
> at org.apache.sshd.common.util.closeable.SequentialCloseable$1.operationComplete(SequentialCloseable.java:45)
> at org.apache.sshd.common.future.AbstractSshFuture.lambda$notifyListener$2(AbstractSshFuture.java:162)
> at org.apache.sshd.common.future.AbstractSshFuture$$Lambda$352/0x0000000800890040.call(Unknown Source)
> at org.apache.sshd.common.util.threads.ThreadUtils.runAsInternal(ThreadUtils.java:66)
> at org.apache.sshd.common.future.AbstractSshFuture.notifyListener(AbstractSshFuture.java:161)
> at org.apache.sshd.common.future.DefaultSshFuture.addListener(DefaultSshFuture.java:166)
> at org.apache.sshd.common.util.closeable.SequentialCloseable$1.operationComplete(SequentialCloseable.java:57)
> at org.apache.sshd.common.util.closeable.SequentialCloseable$1.operationComplete(SequentialCloseable.java:45)
> at org.apache.sshd.common.util.closeable.SequentialCloseable.doClose(SequentialCloseable.java:69)
> at org.apache.sshd.common.util.closeable.SimpleCloseable.close(SimpleCloseable.java:63)
> at org.apache.sshd.common.util.closeable.AbstractInnerCloseable.doCloseGracefully(AbstractInnerCloseable.java:41)
> at org.apache.sshd.common.util.closeable.AbstractCloseable.close(AbstractCloseable.java:110)
> at org.apache.sshd.server.channel.ChannelSession.closeShell(ChannelSession.java:916)
> at org.apache.sshd.server.channel.ChannelSession.lambda$prepareCommand$0(ChannelSession.java:779)
> at org.apache.sshd.server.channel.ChannelSession$$Lambda$414/0x00000008008fa440.onExit(Unknown Source)
> {code}
> The lock is acquired in "KeyExchangeMessageHandler.writeOrEnqueue" and then tries to re-acquire in "KeyExchangeMessageHandler.updateState"
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