linux-kernel - Re: [PATCH] MIPS: Provide fallback reboot/poweroff/halt implementations

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Date:	Tue, 24 Mar 2015 09:30:51 -0700
From:	Andrew Bresticker <abrestic@...omium.org>
To:	James Hogan <james.hogan@...tec.com>
Cc:	Ralf Baechle <ralf@...ux-mips.org>,
	Linux-MIPS <linux-mips@...ux-mips.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] MIPS: Provide fallback reboot/poweroff/halt implementations

Hi James,

On Tue, Mar 24, 2015 at 7:22 AM, James Hogan <james.hogan@...tec.com> wrote:
> Hi Andrew,
>
> On 04/03/15 23:59, Andrew Bresticker wrote:
>> If a machine-specific hook is not implemented for restart, poweroff,
>> or halt, fall back to halting secondary CPUs, disabling interrupts,
>> and spinning.  In the case of restart, attempt to restart the system
>> via do_kernel_restart() (which will call any registered restart
>> handlers) before halting.
>>
>> Signed-off-by: Andrew Bresticker <abrestic@...omium.org>
>> ---
>>  arch/mips/kernel/reset.c | 20 ++++++++++++++++++++
>>  1 file changed, 20 insertions(+)
>>
>> diff --git a/arch/mips/kernel/reset.c b/arch/mips/kernel/reset.c
>> index 07fc524..87b1f08 100644
>> --- a/arch/mips/kernel/reset.c
>> +++ b/arch/mips/kernel/reset.c
>> @@ -29,16 +29,36 @@ void machine_restart(char *command)
>>  {
>>       if (_machine_restart)
>>               _machine_restart(command);
>> +
>> +#ifdef CONFIG_SMP
>> +     smp_send_stop();
>
> Maybe local_irq_disable should be before smp_send_stop() to avoid
> deadlocks (same below)?
>
> See for example commit 44424c34049f41123a3a8b4853822f47f4ff03a2 ("ARM:
> 7803/1: Fix deadlock scenario with smp_send_stop()").

Ah right, good catch.

>> +#endif
>> +     do_kernel_restart(command);
>> +     pr_emerg("Reboot failed -- System halted\n");
>
> Perhaps we could have a grace period like ARM does here:
>
>> /* Give a grace period for failure to restart of 1s */
>> mdelay(1000);
>
> Otherwise with this patch a reboot on Malta usually shows some/all of
> this pr_emerg message prior to actually restarting. (Arguably thats a
> failing of Malta's _machine_restart not to have a delay... thoughts?).

Yes, I think it's reasonable to put a delay here.

Thanks,
Andrew
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