Deadlock in MutexTransport on shutdown with high volume of messages
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Key: AMQ-1119
URL: https://issues.apache.org/activemq/browse/AMQ-1119
Project: ActiveMQ
Issue Type: Bug
Components: Transport
Affects Versions: 4.0.2, 4.0.1, 4.0
Environment: Windows XP, demand forwarding, failover == true
Reporter: Chris Hofstaedter
I ran into a deadlock in the MutextTransport.oneway(Command command) function
when processing very high message volume (100% cpu utilization) at the time of
a shutdown. I'm running 4.0.2 on WinXP and within a demand forwarding
environment with failover = true.
I did trap this deadlock in the debugger and it looks like two commands are
crossing paths in opposite directions through the MutexTransport. One of the
commands is a MessageDispatch and the other is a ShutdownInfo. Now, when the
ShutdownInfo gets through the MutexTransport first, it tries to shutdown the
background thread of the TcpTransport. However, this thread is currently
servicing the MessageDispatch and is blocked on the MutexTransport. Deadlock.
So, my patch was simply to avoid entering the synchronized(writeMutex) block in
the oneway(Command command) function of MutexTransport if
command.isShutdownInfo() returns true:
if (command.isShutdownInfo())
next.oneway(command);
else
synchronized(writeMutex) {
next.oneway(command);
}
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