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Date:      Sun, 17 May 1998 21:56:32 -0500
From:      Dan Nelson <dnelson@emsphone.com>
To:        Greg Lehey <grog@lemis.com>, Dean Hollister <dean@odyssey.apana.org.au>, FreeBSD Questions <freebsd-questions@FreeBSD.ORG>
Subject:   Re: Wierd zombie process
Message-ID:  <19980517215632.A3501@emsphone.com>
In-Reply-To: <19980518100747.G427@freebie.lemis.com>; from "Greg Lehey" on Mon May 18 10:07:47 GMT 1998
References:  <Pine.BSF.3.96.980517214436.18345B-100000@odyssey.apana.org.au> <19980518100747.G427@freebie.lemis.com>

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In the last episode (May 18), Greg Lehey said:
> On Sun, 17 May 1998 at 21:46:11 +0800, Dean Hollister wrote:
> > Upon trying to clear a jammed line, look at this:
> >
> > bash$ ps -t /dev/cue3
> >
> >   PID  TT  STAT      TIME COMMAND
> > 28294 cue- IEs    0:00.00  (bash)
> > 28993 cue- Z      0:00.00  (sh)
> >
> > I cannot kill either process it would seem. A kill on the first one fails
> > to result in an exit, whilst a kill on the second returns no such pid.
> 
> A zombie is a dead process whose parent is denying it a proper
> burial.  Try the l option to ps:

But the more interesting process is of course the parent process (the
bash one).  The 'E' means that the process is trying to exit but can't. 
In this case, it's probably caused by some output that's trying to
flush itself.  You can force a similar situation on the console by
doing a "locate /", hitting scoll-lock, waiting, then killing the
parent shell of the "locate" process.  

To verify that this is your problem, run "ps axl -t /dev/cue3".  If the
WCHAN column says "ttywai", it's trying to flush output.

To force a flush on a hung serial port to silently fail after a
specified timeout in seconds, try using the comcontrol command:

comcontrol /dev/cue drainwait 180

You should probably edit /etc/rc.serial and enable the drain timeout
for all your dialup lines to keep this from happening in the future.

	-Dan Nelson
	dnelson@emsphone.com

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