linux-kernel - Re: Hang opening a pipe written to by a child, with SIGCHLD

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Message-ID: <20120402185057.GB3029@vicerveza.homeunix.net>
Date:	Mon, 2 Apr 2012 20:50:57 +0200
From:	Lluís Batlle i Rossell <viric@...ic.name>
To:	Shea Levy <shea@...alevy.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Hang opening a pipe written to by a child, with SIGCHLD

On Mon, Apr 02, 2012 at 10:49:10AM -0400, Shea Levy wrote:
> On 04/02/2012 10:46 AM, Lluís Batlle i Rossell wrote:
> >Can anyone reproduce this?
> 
> I've reproduced this on my system as well (3.3). No idea about cause though.
> 

Thank you Shea,

with a little change, adding "sleep 0.1" makes it hang early in all (few)
linuces I tried: Let me know if this helps you reproduce the problem.

As before, hangs under strace, does not hang under 'strace -f'. Sorry if I'm
misunderstanding something.

New script:
----------
#!/bin/sh
                                                                                                                   
PIPE=/tmp/pipe
                                                                                                                   
rm -f $PIPE
mkfifo $PIPE
set -x
                                                                                                                   
spawn() {
    sleep 0.1
    echo DONE > $PIPE
}

spawn &

while true; do
    while read LINE < $PIPE; do
        echo $LINE
        spawn &
    done
done
-----------

Regards,
Lluís.
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