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

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Message-ID: <alpine.LFD.2.01.0910131548280.3404@localhost.localdomain>
Date:	Tue, 13 Oct 2009 15:54:45 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
cc:	Boyan <btanastasov@...oo.co.uk>,
	Frédéric L. W. Meunier 
	<fredlwm@...il.com>, "Justin P. Mattock" <justinmattock@...il.com>,
	Nix <nix@...eri.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, Alan Cox wrote:
> 
> I can't help feeling a mutex might be simpler. It would also then fix
> tiocsti() which is most definitely broken right now and documented as
> racing.

Hmm. Those tty's have too many different locks already.

But maybe we could just have one generic mutex, and use it for termios and 
IO locking. It makes perfect sense to serialize the ->receive_buf() code 
with any termios changes, since termios is what affects _how_ that 
->receive_buf() function works.

I do wonder why tiocsti() doesn't just use the tty buffering layer, 
though? Maybe that harks back to the whole "pty's did things differently" 
thing? Why does it go directly to ->receive_buf() in the first place?

And let's see if my patch even makes a difference. Maybe the breakage is 
somewhere else. The "oh, now we call flush_ldisc() from two different 
contexts" thing seems to be a promising lead, but ...

		Linus
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