linux-kernel - Re: [PATCH v3] panic: keep blinking in spite of long spin timer mode

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Message-Id: <20100617152017.1d939db3.akpm@linux-foundation.org>
Date:	Thu, 17 Jun 2010 15:20:17 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	TAMUKI Shoichi <tamuki@...et.gr.jp>
Cc:	Ingo Molnar <mingo@...e.hu>, Anton Blanchard <anton@...ba.org>,
	Andi Kleen <andi@...stfloor.org>,
	Andy Green <andy@...mcat.com>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] panic: keep blinking in spite of long spin timer
 mode

On Fri, 18 Jun 2010 06:36:31 +0900
TAMUKI Shoichi <tamuki@...et.gr.jp> wrote:

> To keep panic_timeout accuracy when running under a hypervisor, the
> current implementation only spins on long time (1 second) calls to
> mdelay.  That brings a good effect, but the problem is the keyboard
> LEDs don't blink at all on that situation.
> 
> This patch changes to call to panic_blink_enter() between every mdelay
> and keeps blinking in spite of long spin timer mode.
> 
> The default time to call to mdelay is 1ms.  It will be switched to
> longer if the CONFIG_PANIC_LONGSPIN_TIMER kernel configuration option
> is enabled.  This feature is helpful when running under a hypervisor.
> 
> Signed-off-by: TAMUKI Shoichi <tamuki@...et.gr.jp>
> ---
>  Changes since v2.1:
>  - get rid of panicblink= kernel parameter
>  - introduce new kernel config option CONFIG_PANIC_LONGSPIN_TIMER
> 

I still don't get it :(

Why can't we simply do

	for (i = 0; ; i++) {
		(*panic_blink)(i & 1);
		mdelay(250);
		touch_nmi_watchdog();
	}

on all kernels, regardless of virtualisation, etc?
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