linux-kernel - Re: [Bug #14388] keyboard under X with 2.6.31

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Date:	Tue, 13 Oct 2009 18:12:12 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Frédéric L. W. Meunier 
	<fredlwm@...il.com>
cc:	Boyan <btanastasov@...oo.co.uk>,
	"Justin P. Mattock" <justinmattock@...il.com>,
	Nix <nix@...eri.org.uk>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Paul Fulghum <paulkf@...rogate.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Ed Tomlinson <edt@....ca>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Subject: Re: [Bug #14388] keyboard under X with 2.6.31

On Tue, 13 Oct 2009, Frédéric L. W. Meunier wrote:
> 
> For now (more than 3h), it isn't doing any harm. And no keyboard lockups.

I think it was Boyan who said he could trigger it "easily", and everybody 
else had a hard time to reproduce the problem, so I'll consider your "good 
for 3h" to not really be a confirmation either way. But at least it's not 
totally broken.

> BTW, the old version of the patch was funny. It booted, but at the login
> prompt I could only enter the first letter.

Yeah, each time somebody read from a tty, the reading would also get rid 
of all the buffers, but would leave buf.tail set to the last one (that had 
been freed). 

Which then resulted in all subsequent IO going to that tail buffer, but 
nobody ever seeing it, because 'head' was NULL, and would stay that way as 
long as 'tail' existed (which it would until the tty was flushed, which it 
would never be).

So you'd only ever see the first read (which could obviously be more than 
one character, but you'd have to type REALLY FAST to get there ;^)

			Linus
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