linux-kernel - Re: SIGQUIT from tty layer

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Date:	Sat, 11 Jul 2009 14:16:59 +0300
From:	Marius Gedminas <marius@...min.as>
To:	xorg@...ts.freedesktop.org
Cc:	Samuel Thibault <samuel.thibault@...-lyon.org>,
	linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: SIGQUIT from tty layer

On Fri, Jul 10, 2009 at 08:33:46PM +0200, Samuel Thibault wrote:
> Ben Gamari, le Thu 09 Jul 2009 13:18:16 -0400, a écrit :
> > On Thu, Jul 09, 2009 at 05:00:47PM +0200, Samuel Thibault wrote:
> > > SIGQUIT is sent to the X server if the controling tty of the X server
> > > (probably its VT) receives the QUIT character (usually control-\, i.e.
> > > 0x1c)
> > 
> > This, however, would imply that something is sending the character and
> > this something is certainly not me. Where else might this character come
> > from? How might I trace who's writing to the tty?
> 
> Not writing to the tty, but producing input for the tty.  Are you
> using evdev or the legacy kbd driver? 0x1c is the keycode of the enter
> key, maybe your workload happens to restart the keyboard driver, which
> temporarily re-enables signal keys.
> 
> Or maybe it's on another tty, do you have anything beyond /dev/mem,
> /dev/null, /dev/tty7, /dev/agpgart and /dev/dri/card* in
> lsof -p $(pidof Xorg) | grep CHR
> ?

This sounds familiar:

  "a set of 'stty' calls in the init scripts, that (amazingly) reset the
   isig flag on the current vt (which in our case is the X vt). For
   anyone ignorant of the vile mess of consequences that means
   (obviously) your X server gets a SIGQUIT when you press enter."
        -- http://www.gnome.org/~michael/blog/2009-05-29.html

Marius Gedminas
-- 
I'm sure it would be possible to speed apport up a lot, after we're done
making boot and login instantaneous.
                -- Lars Wirzenius

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