Subject: Re: [PATCH] arm64: fix a migrating irq bug when hotplug cpu
To: Yang Yingliang <yangyingliang@huawei.com>,
        linux-arm-kernel@lists.infradead.org
References: <55E1AD09.7020701@huawei.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Marc Zyngier <marc.zyngier@arm.com>,
        Mark Rutland <mark.rutland@arm.com>, Will Deacon <will.deacon@arm.com>,
        linux-kernel@vger.kernel.org
From: Jiang Liu <jiang.liu@linux.intel.com>
Organization: Intel
Message-ID: <55E1CBE9.6080705@linux.intel.com>
Date: Sat, 29 Aug 2015 23:12:41 +0800
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On 2015/8/29 21:00, Yang Yingliang wrote:
> From: Yang Yingliang <yangyingliang@huawei.com>
> 
> When cpu is disabled, all irqs will be migratged to another cpu.
> In some cases, a new affinity is different, it needed to be coppied
> to irq's affinity. But if the type of irq is LPI, it's affinity will
> not be coppied because of irq_set_affinity's return value.
> So copy the affinity, when the return value is IRQ_SET_MASK_OK_DONE.
Hi Yingliang,
	If irq_set_affinity callback returns IRQ_SET_MASK_OK_DONE,
it means that irq_set_affinity has copied the new CPU mask to irq
affinity mask. It would be better to change irq_set_affinity for LPI
to follow this rule.
Thanks!
Gerry
> 
> Cc: Jiang Liu <jiang.liu@linux.intel.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> ---
>  arch/arm64/kernel/irq.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
> index 463fa2e..2acc8ec 100644
> --- a/arch/arm64/kernel/irq.c
> +++ b/arch/arm64/kernel/irq.c
> @@ -78,10 +78,13 @@ static bool migrate_one_irq(struct irq_desc *desc)
>      }
> 
>      c = irq_data_get_irq_chip(d);
> -    if (!c->irq_set_affinity)
> +    if (!c->irq_set_affinity) {
>          pr_debug("IRQ%u: unable to set affinity\n", d->irq);
> -    else if (c->irq_set_affinity(d, affinity, false) == IRQ_SET_MASK_OK
> && ret)
> -        cpumask_copy(irq_data_get_affinity_mask(d), affinity);
> +    } else if (c->irq_set_affinity(d, affinity, false) ==
> IRQ_SET_MASK_OK && ret) {
> +        int r = c->irq_set_affinity(d, affinity, false);
> +        if ((r == IRQ_SET_MASK_OK || r == IRQ_SET_MASK_OK_DONE) && ret)
> +            cpumask_copy(irq_data_get_affinity_mask(d), affinity);
> +    }
> 
>      return ret;
>  }
--
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