Date: Wed, 19 Jan 2005 16:47:10 +0100 From: Raymond Wiker <Raymond.Wiker@fast.no> To: Rob <spamrefuse@yahoo.com> Cc: freebsd-stable@freebsd.org Subject: Re: User's cron job creates zombie process on 5.3 Message-ID: <16878.33022.866459.717977@raw.grenland.fast.no> In-Reply-To: <41EE7C44.2010407@yahoo.com> References: <41EE7C44.2010407@yahoo.com>
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Rob writes:
> Raymond Wiker wrote:
> > Peter Jeremy writes:
> > > On Wed, 2005-Jan-19 09:16:59 +0900, Rob Lahaye wrote:
> > > > tunnel="-L 55110:localhost:110 pop3.univ.net"
> > > > tunnel_up=`pgrep -f -- "${tunnel}"`
> > > > [ "${tunnel_up}" = "" ] && /usr/bin/ssh -N -f ${tunnel}
> > >
> > > >It works beautifully, but why does this also generate one zombie process:
> > > > USER PID %CPU %MEM VSZ RSS TT STAT STARTED TIME COMMAND
> > > > rob 655 0.0 0.0 0 0 ?? Z Sat02PM 0:00.01 <defunct>
> > >
> > > You get a zombie when a process has exited and the parent hasn't issued
> > > a wait(2) (or SIG_IGN'd SIGCHLD). Have a look at what the parent process
> > > is and that might give you an idea as to what is going wrong.
> >
> > Ancient Perl did not collect for children started via the
> > backtick operator - is this a possible issue for /bin/sh as well? It
> > should be harmless to call wait just after the use of the backtick
> > operator above; does that change anything? I.e:
> >
> > tunnel_up=`pgrep -f -- "${tunnel}"`; wait
> >
> > To see the parent pid, add "-O ppid" to the arguments to ps;
> > e.g,
> >
> > ps axww -O ppid
>
> Adding the "wait" here does not help at all.
>
> When I verify the parent process I have this:
>
> PID PPID TT STAT TIME COMMAND USER %CPU %MEM VSZ RSS STARTED
> 423 417 ?? I 0:00.00 cron: running jo root 0.0 0.2 1360 1148 11:38PM
> 425 423 ?? Z 0:00.00 <defunct> lahaye 0.0 0.0 0 0 11:38PM
>
>
> So PID 423 "cron: running job (cron)" is the parent of my <defunct> zombie.
>
> After playing with commenting out lines, I found out that the ssh call is the
> reason for the zombie: "/usr/bin/ssh -N -f -L 55110:localhost:110 pop3.univ.net"
>
> Then I tried exec : "exec /usr/bin/ssh -N -f ..."
> And I also tried & : "/usr/bin/ssh -N -f ... &"
> Both to no avail.
>
> What else can I try, and why is this ssh command causing a zombie process when
> called from cron?
Hmm... Maybe this will work?
/bin/sh -c "/usr/bin/ssh -n -f ${tunnel} &"
--- the effect of this should (hopefully) be that init becomes the
parent of the zombie process.
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