linux-kernel - Re: [PATCH 9/11] Panic delay fix

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Message-ID: <d120d5000702150535w1ec29473x5d173704389811aa@mail.gmail.com>
Date:	Thu, 15 Feb 2007 08:35:42 -0500
From:	"Dmitry Torokhov" <dmitry.torokhov@...il.com>
To:	"Rusty Russell" <rusty@...tcorp.com.au>
Cc:	"Zachary Amsden" <zach@...are.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akp=m@...l.org>, "Andi Kleen" <ak@....de>,
	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	"Chris Wright" <chrisw@...s-sol.org>,
	Alan <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH 9/11] Panic delay fix

On 2/14/07, Rusty Russell <rusty@...tcorp.com.au> wrote:
> On Mon, 2007-02-05 at 19:53 -0800, Zachary Amsden wrote:
> > Failure to use real-time delay here causes the keyboard to become demonically
> > possessed in the event of a kernel crash, with wildly blinking lights and
> > unpredictable behavior.  This has resulted in several injuries.
>
> The problem is the normal one when we introduce a new concept into the
> kernel; there are two kinds of udelay, and they've been conflated.  The
> most common case is a delay for real hardware devices; this can be
> eliminated for paravirtualization.  The other cases, the tiny minority,
> are visible delays (keyboard leds), not knowing if they're necessary
> (very early boot), and async events (other CPUs coming up): ie.
> everything else.
>

Just for the record - I believe that i8042 is fine as is now. The only
place where real delay needs to be enforced is panic.c - it should
call panic blink routine once every 1 ms.

-- 
Dmitry
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