[Octave-bug-tracker] [bug #42665] Windows (Xming) gnuplot viewers crash, leaving defunct processes on host machine

[Mike Miller]

Update of bug #42665 (project octave):

              Item Group:                   Crash => Other                  
                  Status:               Need Info => Duplicate              
             Open/Closed:                    Open => Closed                 
              Depends on:                         => bugs #37591            

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Follow-up Comment #6:

Yes, this is the same behavior I observe (except I can't figure out how to
close an SSH session while leaving the octave process running on the remote).

The reason for zombie processes is that the gnuplot process has exited
(probably because gnuplot detected that your DISPLAY disconnected) but Octave
is still running and has not cleaned up the child process resources that it
spawned. I can achieve the same result in a desktop session by simply plotting
a gnuplot figure and then killing the gnuplot process outside of Octave. But
once Octave is killed, the zombies are taken care of by the system. This is
standard expected Unix behavior.

So I think this is only partly a bug in Octave, but the main issue you're
having is that the connection is closed, killing gnuplot but not killing
Octave. You should either arrange for your users to "close all" before
exiting, or to actually exit Octave before closing putty, figure out how to
make putty close the SSH session properly, or have a cleanup process on the
server that takes care of leftover Octave processes that users have left
behind after logging off. Having leftover unused running Octave sessions seems
more wasteful and serious to me than defunct gnuplot processes. Fix that
problem with your workflow and you won't have zombie processes on your
system.

There is already another bug about Octave creating zombie processes in a
different way, so I'll close this bug as a duplicate of bug #37591. The
eventual fix for that bug may mean no more gnuplot processes left over, but
that's not the real problem with your setup.

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