Re: [PATCH 2/2] irqchip/sifive-plic: Fix the interrupt was enabled accidentally issue.

From: Marc Zyngier <maz@kernel.org>
To: Greentime Hu <greentime.hu@sifive.com>
Cc: jason@lakedaemon.net, linux-kernel@vger.kernel.org,
	palmer@dabbelt.com, paul.walmsley@sifive.com, tglx@linutronix.de,
	linux-riscv@lists.infradead.org
Subject: Re: [PATCH 2/2] irqchip/sifive-plic: Fix the interrupt was enabled accidentally issue.
Date: Thu, 15 Oct 2020 22:23:40 +0100	[thread overview]
Message-ID: <5bedfbc723665c979eb73eefadb21970@kernel.org> (raw)
In-Reply-To: <20201012135724.110579-2-greentime.hu@sifive.com>

On 2020-10-12 14:57, Greentime Hu wrote:
> In commit 2ca0b460bbcb ("genirq/affinity: Make affinity setting if
> activated opt-in"),
> it added irqd_affinity_on_activate() checking in the function
> irq_set_affinity_deactivated() so it will return false here.
> In that case, it will call irq_try_set_affinity() -> plic_irq_toggle()
> which will enable the interrupt to cause the CPU hang.
> 
> 	if (irq_set_affinity_deactivated())
> 		return 0;
> 	...
> 	irq_try_set_affinity(data, mask, force);
> 
> [  919.015783] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> [  919.020922] rcu:     0-...0: (0 ticks this GP)
> idle=7d2/1/0x4000000000000002 softirq=1424/1424 fqs=105807
> [  919.030295]  (detected by 1, t=225825 jiffies, g=1561, q=3496)
> [  919.036109] Task dump for CPU 0:
> [  919.039321] kworker/0:1     R  running task        0    30      2 
> 0x00000008
> [  919.046359] Workqueue: events set_brightness_delayed
> [  919.051302] Call Trace:
> [  919.053738] [<ffffffe000930d92>] __schedule+0x194/0x4de
> [  982.035783] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> [  982.040923] rcu:     0-...0: (0 ticks this GP)
> idle=7d2/1/0x4000000000000002 softirq=1424/1424 fqs=113325
> [  982.050294]  (detected by 1, t=241580 jiffies, g=1561, q=3509)
> [  982.056108] Task dump for CPU 0:
> [  982.059321] kworker/0:1     R  running task        0    30      2 
> 0x00000008
> [  982.066359] Workqueue: events set_brightness_delayed
> [  982.071302] Call Trace:
> [  982.073739] [<ffffffe000930d92>] __schedule+0x194/0x4de
> [..]
> 
> After applying this patch, the CPU hang issue can be fixed.
> 
> Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
> ---
>  drivers/irqchip/irq-sifive-plic.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/irqchip/irq-sifive-plic.c
> b/drivers/irqchip/irq-sifive-plic.c
> index 4cc8a2657a6d..8a673d9cff69 100644
> --- a/drivers/irqchip/irq-sifive-plic.c
> +++ b/drivers/irqchip/irq-sifive-plic.c
> @@ -183,10 +183,14 @@ static int plic_irqdomain_map(struct irq_domain
> *d, unsigned int irq,
>  			      irq_hw_number_t hwirq)
>  {
>  	struct plic_priv *priv = d->host_data;
> +	struct irq_data *irqd;
> 
>  	irq_domain_set_info(d, irq, hwirq, &plic_chip, d->host_data,
>  			    handle_fasteoi_irq, NULL, NULL);
>  	irq_set_noprobe(irq);
> +	irqd = irq_get_irq_data(irq);
> +	irqd_set_single_target(irqd);
> +	irqd_set_affinity_on_activate(irqd);
>  	irq_set_affinity(irq, &priv->lmask);
>  	return 0;
>  }

How does this fix anything? The plic driver doesn't have an activate
callback, so how does it make any difference? I get the feeling this
papers over another issue.

         M.
-- 
Jazz is not dead. It just smells funny...

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