linux-kernel - Re: [PATCH v6 3/7] arm: Support restart through restart handler call chain

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Date:	Sat, 09 Aug 2014 14:11:08 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Heiko Stübner <heiko@...ech.de>
CC:	linux-watchdog@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Wim Van Sebroeck <wim@...ana.be>,
	Catalin Marinas <catalin.marinas@....com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Will Deacon <will.deacon@....com>,
	Arnd Bergmann <arnd@...db.de>,
	Russell King <linux@....linux.org.uk>,
	Jonas Jensen <jonas.jensen@...il.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Tomasz Figa <t.figa@...sung.com>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 3/7] arm: Support restart through restart handler call
 chain

On 08/09/2014 01:01 PM, Heiko Stübner wrote:
> Hi Guenter,
>
> Am Montag, 4. August 2014, 18:48:54 schrieb Guenter Roeck:
>> The kernel core now supports a restart handler call chain for system
>> restart functions.
>>
>> With this change, the arm_pm_restart callback is now optional, so check
>> if it is set before calling it. Only call the kernel restart handler
>> if arm_pm_restart is not set.
>>
>> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>> Acked-by: Catalin Marinas <catalin.marinas@....com>
>> Acked-by: Heiko Stuebner <heiko@...ech.de>
>> ---
>> v6: No change.
>> v5: Renamed restart function to do_kernel_restart
>> v4: No change.
>> v3: Use wrapper function to execute notifier call chain.
>> v2: Only call notifier call chain if arm_pm_restart is not set.
>>      Do not include linux/watchdog.h.
>>
>>   arch/arm/kernel/process.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
>> index 81ef686..84ca0d5 100644
>> --- a/arch/arm/kernel/process.c
>> +++ b/arch/arm/kernel/process.c
>> @@ -230,7 +230,10 @@ void machine_restart(char *cmd)
>>   	local_irq_disable();
>>   	smp_send_stop();
>>
>> -	arm_pm_restart(reboot_mode, cmd);
>> +	if (arm_pm_restart)
>> +		arm_pm_restart(reboot_mode, cmd);
>> +	else
>> +		do_kernel_restart(cmd);
>>
>>   	/* Give a grace period for failure to restart of 1s */
>>   	mdelay(1000);
>
> shouldn't you also get rid of
>
> 	void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd) = null_restart;
>
Yes. Looks like I'll need another revision.

Even worse, the current upstream code is somewhat broken and doesn't really
like the following instructions.
	drivers/watchdog/moxart_wdt.c:  arm_pm_restart = NULL;
	drivers/watchdog/sunxi_wdt.c:   arm_pm_restart = NULL;

Fortunately that code is only executed if those drivers are built as modules
and unloaded.

Guenter

> like a previous attempt at unifying the restart handling [0] did.
>
> Because when testing the current series on my Rockchip boards, there was
> always an arm_pm_restart defined ... namely the null_restart mentioned above.
> So do_kernel_restart is never reached until I disable the null_restart.
>
>
> Heiko
>
>
> [0] http://permalink.gmane.org/gmane.linux.ports.arm.kernel/277042
>
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>

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