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From:   Anup Patel <anup@brainfault.org>
Date:   Fri, 23 Oct 2020 16:57:41 +0530
Message-ID: <CAAhSdy120ZR4ZbkHo8Us+CugaeegSR6iFu9jgHPuyvDAQwnOhQ@mail.gmail.com>
Subject: Re: [PATCH 2/3] irqchip/irq-sifive-plic: Fixup couldn't broadcast to
 multi CPUs
To:     Guo Ren <guoren@kernel.org>
Cc:     Palmer Dabbelt <palmerdabbelt@google.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Greentime Hu <greentime.hu@sifive.com>,
        Zong Li <zong.li@sifive.com>,
        Atish Patra <atish.patra@wdc.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>,
        Marc Zyngier <maz@kernel.org>, wesley@sifive.com,
        Yash Shah <yash.shah@sifive.com>,
        Christoph Hellwig <hch@lst.de>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>,
        Guo Ren <guoren@linux.alibaba.com>
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On Fri, Oct 23, 2020 at 3:48 PM <guoren@kernel.org> wrote:
>
> From: Guo Ren <guoren@linux.alibaba.com>
>
> If "echo 3 > /proc/irq/1/smp_affinity", we want irq 1 could be
> broadcast to CPU0 & CPU1 and one of them would pick up the irq
> handler.
>
> But current implementation couldn't let multi CPUs process the
> same IRQ concurrent.
>
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> ---
>  drivers/irqchip/irq-sifive-plic.c | 23 ++++++-----------------
>  1 file changed, 6 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> index 2e56576..0003322 100644
> --- a/drivers/irqchip/irq-sifive-plic.c
> +++ b/drivers/irqchip/irq-sifive-plic.c
> @@ -114,15 +114,12 @@ static inline void plic_irq_toggle(const struct cpumask *mask,
>  static void plic_irq_unmask(struct irq_data *d)
>  {
>         struct cpumask amask;
> -       unsigned int cpu;
>         struct plic_priv *priv = irq_get_chip_data(d->irq);
>
>         cpumask_and(&amask, &priv->lmask, cpu_online_mask);
> -       cpu = cpumask_any_and(irq_data_get_affinity_mask(d),
> -                                          &amask);
> -       if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
> -               return;
> -       plic_irq_toggle(cpumask_of(cpu), d, 1);
> +       cpumask_and(&amask, &amask, irq_data_get_affinity_mask(d));
> +
> +       plic_irq_toggle(&amask, d, 1);
>  }
>
>  static void plic_irq_mask(struct irq_data *d)
> @@ -136,24 +133,16 @@ static void plic_irq_mask(struct irq_data *d)
>  static int plic_set_affinity(struct irq_data *d,
>                              const struct cpumask *mask_val, bool force)
>  {
> -       unsigned int cpu;
>         struct cpumask amask;
>         struct plic_priv *priv = irq_get_chip_data(d->irq);
>
>         cpumask_and(&amask, &priv->lmask, mask_val);
> +       cpumask_and(&amask, &amask, cpu_online_mask);
>
> -       if (force)
> -               cpu = cpumask_first(&amask);
> -       else
> -               cpu = cpumask_any_and(&amask, cpu_online_mask);
> -
> -       if (cpu >= nr_cpu_ids)
> -               return -EINVAL;
> +       irq_data_update_effective_affinity(d, &amask);
>
>         plic_irq_toggle(&priv->lmask, d, 0);
> -       plic_irq_toggle(cpumask_of(cpu), d, 1);
> -
> -       irq_data_update_effective_affinity(d, cpumask_of(cpu));
> +       plic_irq_toggle(&amask, d, 1);
>
>         return IRQ_SET_MASK_OK_DONE;
>  }
> --
> 2.7.4
>

In the past, a similar patch was proposed by Zong Li (SiFive). We
have good reasons to not allow multiple CPUs handle the same IRQ.

Refer, https://lkml.org/lkml/2020/4/26/201

NACK from my side.

Regards,
Anup