linux-kernel - Re: Wait for console to become available, v3.2

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Date:	Tue, 21 Apr 2009 18:41:05 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	David VomLehn <dvomlehn@...co.com>
Cc:	David Brownell <david-b@...bell.net>, alan@...rguk.ukuu.org.uk,
	Ingo Molnar <mingo@...e.hu>,
	Arjan van de Ven <arjan@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	Linux Embedded Mailing List <linux-embedded@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Wait for console to become available, v3.2

On Tue, 2009-04-21 at 10:29 -0700, David VomLehn wrote:
> On Tue, Apr 21, 2009 at 06:11:11PM +0100, David Woodhouse wrote:
> ...
> > The kernel output is going to be spewed when a console registers with
> > CON_PRINTBUFFER anyway, and if we printk a warning about userspace
> > console output being lost, that ought to be good enough to notify the
> > user that something may have been lost. For bonus points, we could even
> > make that 'dummy' tty driver buffer a limited amount of userspace
> > output, maybe.
> 
> What in the world are users going to do when they see a message about
> output being lost? There is no way to recover the data and no way to
> prevent it in the future. I don't think this is a good approach.
> 
> Remember, even though the previous functionality of USB consoles was, in
> theory, less reliable than it appeared, it actually has been working well
> for years. Thus, tossing output will count as a regression for most of the
> world.

So implement a small amount of buffering, as I suggested, and it should
be sufficient to cover the cases that were only working before by blind
luck anyway.

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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