linux-kernel - Re: [PATCH v7 2/2] ARM hibernation / suspend-to-disk

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Message-ID: <5331CD43.1010601@ahsoftware.de>
Date:	Tue, 25 Mar 2014 19:38:59 +0100
From:	Alexander Holler <holler@...oftware.de>
To:	Sebastian Capella <sebastian.capella@...aro.org>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Len Brown <len.brown@...el.com>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Russell King <linux@....linux.org.uk>,
	Jonathan Austin <jonathan.austin@....com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Victor Kamensky <victor.kamensky@...aro.org>,
	Will Deacon <will.deacon@....com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Sricharan R <r.sricharan@...com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Russ Dill <Russ.Dill@...com>, Nicolas Pitre <nico@...aro.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Laura Abbott <lauraa@...eaurora.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Jiang Liu <liuj97@...il.com>
Subject: Re: [PATCH v7 2/2] ARM hibernation / suspend-to-disk

Am 19.03.2014 22:06, schrieb Sebastian Capella:
> On 19 March 2014 13:47, Sebastian Capella <sebastian.capella@...aro.org> wrote:
>> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
>> index a5f702a..d96b910 100644
>> --- a/kernel/power/hibernate.c
>> +++ b/kernel/power/hibernate.c
>> @@ -594,7 +594,8 @@ static void power_down(void)
>>          case HIBERNATION_PLATFORM:
>>                  hibernation_platform_enter();
>>          case HIBERNATION_SHUTDOWN:
>> -               kernel_power_off();
>> +               if (pm_power_off)
>> +                       kernel_power_off();
>>                  break;
>>   #ifdef CONFIG_SUSPEND
>>          case HIBERNATION_SUSPEND:
>>
>>
>> This follows the behavior in the reboot syscall which does it this way
>> also.  I'm testing this now, and it seems work fine.  If this looks
>> good, I can add it as an additional patch.
>
> BTW, one thing I would point out is that kernel_power_off and
> kernel_halt call the same notifier but with different parameters
> (SYS_POWER_OFF and SYS_HALT).
>
> If pm_power_down is null, I dont see why we'd want to notify
> SYS_POWER_OFF before SYS_HALT.  With the previous change I'm assuming
> there's no benefit, so please chime in if you know a reason.

Both states, power off and sys halt, do sound pretty final and I would 
assume something is broken, if power off is called before sys halt or 
vice versa. At least I would never expect that the 
reboot/poweroff/syshalt notifier may be called twice (and thats why the 
heartbeat-trigger may crash).

But just in case, changing that behaviour in ledtrig-heartbeat.c would 
be pretty easy, just remove the heartbeat_reboot_notifier (which plays 
nice and deregisters the trigger on reboot) and use the panic_notifier 
(which doesn't unregister the trigger but just turns off the led) for 
reboot too. Another solution would be to unregister the reboot_notifier 
in the reboot_nofifier itself. I've just seen one watchdog driver 
(drivers/rtc/rtc-m41t80.c) which does that. But I still think such 
shouldn't be necessary (and I haven't had a look at other 
reboot_notifier users).


Regards,

Alexander Holler
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