linux-kernel - Re: [bug] WARNING: at drivers/char/tty_io.c:1266 tty

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Date:	Tue, 16 Jun 2009 10:49:52 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	linux-kernel@...r.kernel.org,
	Pekka Enberg <penberg@...helsinki.fi>,
	Vegard Nossum <vegard.nossum@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [bug] WARNING: at drivers/char/tty_io.c:1266
	tty_open+0x1ea/0x388()


* Alan Cox <alan@...rguk.ukuu.org.uk> wrote:

> > > I split the ldisc and tty apart and redid the ldisc locking so its a fair
> > > bet I know what changeset is to blame, will just need to hunt it down a
> > > bit. kmemcheck found one leak case on Friday which I've fixed but not yet
> > > scribbles.
> > > 
> > > >  c65c9bc: tty: rewrite the ldisc locking
> > > 
> > > Almost certainly that one and will investigate on Monday
> > 
> > I have applied your patch from yesterday (attached further below for 
> > reference) and the SLAB corruption has not triggered - instead i'm 
> > now getting this warning, after 96 reboots:
> 
> That's progress
> 
> > Another test-box has produced this warning too. (Same config and 
> > same hw as i sent the details for earlier in this thread.)
> > 
> > So there's still something fishy going on.
> 
> Are you using a standard udev/fedora setup or something different 
> (I know the devtmpfs proposal stuff produces crashes like that one 
> all the time which are not seen anywhere else)
> 
> And is it reproducable this time - and always 96 ?

It shows up randomly and on multiple systems.

I'm wondering, how long have these patches been in linux-next? Has 
no-one reported an easy (or easier) reproducer than a plain bootup 
(which really doesnt hit the tty code intentionally hard)?

You should probably also write testcases and stress-tests if you 
modify code in this area.

	Ingo
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