linux-kernel - Re: [PATCH] [ARM] Unconditional call to smp_cross

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Date:	Wed, 23 May 2012 10:45:44 -0700
From:	Russ Dill <Russ.Dill@...com>
To:	Pantelis Antoniou <panto@...oniou-consulting.com>
CC:	<linux-kernel@...r.kernel.org>, <linux@....linux.org.uk>,
	<mporter@...com>
Subject: Re: [PATCH] [ARM] Unconditional call to smp_cross_call on UP crashes

On 05/24/2012 10:09 AM, Pantelis Antoniou wrote:
> omap2plus_defconfig builds with SMP & SMP_ON_UP set.
> On beagle (which is UP) is_smp() returns false and we don't call
> smp_init_cpus which in turn does not initialize smp_cross_call which
> remains NULL.
>
> When issuing a reboot we OOPS with a NULL dereference on stop smp_call.
>
> Fixed by checking is_smp in smp_send_stop()
> ---
>  arch/arm/kernel/smp.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)

Acked-by: Russ.Dill@...com

> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index 8f46446..2a61335 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -588,6 +588,10 @@ void smp_send_stop(void)
>  	unsigned long timeout;
>  	struct cpumask mask;
>  
> +	/* make sure we don't bother if not SMP */
> +	if (!is_smp())
> +		return;
> +
>  	cpumask_copy(&mask, cpu_online_mask);
>  	cpumask_clear_cpu(smp_processor_id(), &mask);
>  	smp_cross_call(&mask, IPI_CPU_STOP);


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