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

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Date:	Wed, 23 May 2012 18:55:23 +0000
From:	"Porter, Matt" <mporter@...com>
To:	Pantelis Antoniou <panto@...oniou-consulting.com>
CC:	"<linux-kernel@...r.kernel.org>" <linux-kernel@...r.kernel.org>,
	"<linux@....linux.org.uk>" <linux@....linux.org.uk>,
	"Dill, Russ" <russ.dill@...com>
Subject: Re: [PATCH] [ARM] Unconditional call to smp_cross_call on UP crashes

On May 24, 2012, at 1:09 PM, 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()

Please also add Cc: stable@...r.kernel.org in the sign offs
so it's picked up in stable.

Tested-by: Matt Porter <mporter@...com>

> ---
> arch/arm/kernel/smp.c |    4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
> 
> 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);
> -- 
> 1.7.1
> 

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