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

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Date:	Tue, 24 Mar 2015 14:22:22 +0000
From:	James Hogan <james.hogan@...tec.com>
To:	Andrew Bresticker <abrestic@...omium.org>,
	Ralf Baechle <ralf@...ux-mips.org>
CC:	<linux-mips@...ux-mips.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] MIPS: Provide fallback reboot/poweroff/halt implementations

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()").

> +#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?).

Cheers
James

> +	local_irq_disable();
> +	while (1);
>  }
>  
>  void machine_halt(void)
>  {
>  	if (_machine_halt)
>  		_machine_halt();
> +
> +#ifdef CONFIG_SMP
> +	smp_send_stop();
> +#endif
> +	local_irq_disable();
> +	while (1);
>  }
>  
>  void machine_power_off(void)
>  {
>  	if (pm_power_off)
>  		pm_power_off();
> +
> +#ifdef CONFIG_SMP
> +	smp_send_stop();
> +#endif
> +	local_irq_disable();
> +	while (1);
>  }
> 


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