Subject: [PATCH] arm: use cpu_online_mask when using forced irq_set_affinity

From: [email-masked] (Sudeep Holla)
Date: Fri, 23 May 2014 12:26:02 +0100

Hi Russell,

On 09/05/14 17:40, Sudeep Holla wrote:
> From: Sudeep Holla <[email-masked]>
>
> Commit 01f8fa4f01d8("genirq: Allow forcing cpu affinity of interrupts")
> enabled the forced irq_set_affinity which previously refused to route an
> interrupt to an offline cpu.
>
> Commit ffde1de64012("irqchip: Gic: Support forced affinity setting")
> implements this force logic and disables the cpu online check for GIC
> interrupt controller.
>
> When __cpu_disable calls migrate_irqs, it disables the current cpu in
> cpu_online_mask and uses forced irq_set_affinity to migrate the IRQs
> away from the cpu but passes affinity mask with the cpu being offlined
> also included in it.
>
> When calling irq_set_affinity with force == true in a cpu hotplug path,
> the caller must ensure that the cpu being offlined is not present in the
> affinity mask or it may be selected as the target CPU, leading to the
> interrupt not being migrated.
>
> This patch uses cpu_online_mask when using forced irq_set_affinity so
> that the IRQs are properly migrated away.
>
> Tested on TC2 hotpluging CPU0 in and out. Without this patch the system
> locks up as the IRQs are not migrated away from CPU0.
>

If you are fine with this change, can I put this in the patch tracker?

Regards,
Sudeep

> Cc: Russell King <[email-masked]>
> Acked-by: Mark Rutland <[email-masked]>
> Signed-off-by: Sudeep Holla <[email-masked]>
> ---
>   arch/arm/kernel/irq.c | 10 +++++++---
>   1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c
> index 9723d17..1f216a5 100644
> --- a/arch/arm/kernel/irq.c
> +++ b/arch/arm/kernel/irq.c
> @@ -155,11 +155,15 @@ static bool migrate_one_irq(struct irq_desc *desc)
>   	if (irqd_is_per_cpu(d) || !cpumask_test_cpu(smp_processor_id(), affinity))
>   		return false;
>
> -	if (cpumask_any_and(affinity, cpu_online_mask) >= nr_cpu_ids) {
> -		affinity = cpu_online_mask;
> +	if (cpumask_any_and(affinity, cpu_online_mask) >= nr_cpu_ids)
>   		ret = true;
> -	}
>
> +	/*
> +	 * when using forced irq_set_affinity we must ensure that the cpu
> +	 * being offlined is not present in the affinity mask, it may be
> +	 * selected as the target CPU otherwise
> +	 */
> +	affinity = cpu_online_mask;
>   	c = irq_data_get_irq_chip(d);
>   	if (!c->irq_set_affinity)
>   		pr_debug("IRQ%u: unable to set affinity\n", d->irq);
>