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

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Date:	Mon, 21 Jun 2010 07:52:09 +0900
From:	TAMUKI Shoichi <tamuki@...et.gr.jp>
To:	Andrew Morton <akpm@...ux-foundation.org>
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>,
	TAMUKI Shoichi <tamuki@...et.gr.jp>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] panic: keep blinking in spite of long spin timer mode

Hello,

On Thu, 17 Jun 2010 15:20:17 -0700 Andrew Morton 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?

OK, I will commonize the time to call to mdelay() on the native case
and the hypervisor case, and get rid of the kernel config option.  I
will adjust it to 100ms so as to keep the interval to call to touch_
nmi_watchdog() or touch_softlockup_watchdog() as much as possible.
Even this change will keep panic_timeout accuracy enough when running
under a hypervisor.

Thank you for the suggestion.  See you next PATCH v4.

Regards,
TAMUKI Shoichi
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