linux-kernel - Re: [PATCH] ARM: machine_power

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Date:	Tue, 25 Mar 2014 19:45:55 -0300
From:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To:	Sebastian Capella <sebastian.capella@...aro.org>,
	Russell King <linux@....linux.org.uk>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	linaro-kernel@...ts.linaro.org, Len Brown <len.brown@...el.com>,
	Pavel Machek <pavel@....cz>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: machine_power_off should not return

Let's Cc: LAKML, and To: Russell.

Russell, any comments on this?

Without this patch we got the heartbeat's reboot_notifier called twice while
testing the recent hibernation patches, which was unexpected and produced a
kernel panic: https://lkml.org/lkml/2014/3/19/363

Instead of fixing the heartbeat LED trigger, or the hibernation code, it
seems better to fix the ARM machine_power_off, as it's not supposed to return.

On Mar 24, Sebastian Capella wrote:
> Add loop to prevent return from machine_power_off if
> pm_power_off is null or does not halt the system.
> This caused a panic during hibernation testing on Kirkwood
> Openblocks A6 board.
> 
> Signed-off-by: Sebastian Capella <sebastian.capella@...aro.org>
> Reported-by: Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
> Cc: Len Brown <len.brown@...el.com>
> Cc: Pavel Machek <pavel@....cz>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> ---
>  arch/arm/kernel/process.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
> index f58b723..6ffdc2c 100644
> --- a/arch/arm/kernel/process.c
> +++ b/arch/arm/kernel/process.c
> @@ -217,6 +217,8 @@ void machine_power_off(void)
>  
>  	if (pm_power_off)
>  		pm_power_off();
> +	while (1)
> +		cpu_relax();
>  }
>  
>  /*
> -- 
> 1.7.9.5
> 
> --
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-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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