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

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Date:	Wed, 2 Jun 2010 11:34:46 -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>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] panic: keep blinking in spite of long spin timer mode

On Fri, 28 May 2010 06:56:45 +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 we must give up blinking even
> if we have a panic_blink.
> 
> This patch keeps blinking in spite of long spin timer mode.
> 
> We now have new kernel parameter (panic_longspin) to enable long spin
> timer mode when kernel panics.  This is to be used when running under
> a hypervisor (default is disable).

The whole panic-blink setup seems rather poorly thought out.

Would it not be better if a call to (*panic_blink)() were to simply set
the state of the LED and then return?  So callers can do

	int state = 0;

	for ( ; ; ) {
		(*panic_blink)(state);
		state ^= 1;
		mdelay(MSEC_PER_SEC);
	}

?
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