linux-kernel - Re: [PATCH] hvc_console: fix dropping of characters when output byte channel is full

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Message-ID: <20100914150539.45c0672e@schlenkerla.am.freescale.net>
Date:	Tue, 14 Sep 2010 15:05:39 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	kumar.gala@...escale.com, linux-kernel@...r.kernel.org,
	linuxppc-dev@...abs.org, amit.shah@...hat.com,
	Timur Tabi <timur@...escale.com>
Subject: Re: [PATCH] hvc_console: fix dropping of characters when output
 byte channel is full

On Tue, 14 Sep 2010 20:44:10 +0100
Alan Cox <alan@...rguk.ukuu.org.uk> wrote:

> > Yes, hvc_push() reschedules.  It doesn't sit in a tight loop burning
> > electrons!
> > 
> > Can we do something safer&smarter here?
> 
> 
> Its a printk handler - better to lose the bytes than hang the box. I
> think the current code is probably right.

Losing the bytes is unacceptable.  Even if an hvc backend erroneously
returns zero on a permanent error, the timeout should prevent hanging
the box for too long.

Though I suspect the right answer for us may be "don't use the hvc
layer".

-Scott

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