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From: Paul Burton <paulburton@kernel.org>
To: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: linux-mips@vger.kernel.org, chenhc@lemote.com,
	paul.burton@mips.com, tglx@linutronix.de, jason@lakedaemon.net,
	maz@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] irqchip: mips-cpu: Remove eoi operation
Date: Tue, 14 Jan 2020 15:30:25 -0800	[thread overview]
Message-ID: <20200114233025.y4azwvivqo7kg7i5@pburton-laptop> (raw)
In-Reply-To: <20200113101251.37471-1-jiaxun.yang@flygoat.com>

Hi Jiaxun,

On Mon, Jan 13, 2020 at 06:12:51PM +0800, Jiaxun Yang wrote:
> The eoi opreation in mips_cpu_irq_controller caused chained_irq_enter
> falsely consider CPU IP interrupt as a FastEOI type IRQ. So the interrupt
> won't be masked during in handler. Which might lead to spurious interrupt.
> 
> Thus we simply remove eoi operation for mips_cpu_irq_controller,
> 
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---
>  drivers/irqchip/irq-mips-cpu.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-mips-cpu.c b/drivers/irqchip/irq-mips-cpu.c
> index 95d4fd8f7a96..0ad7f1f9a58b 100644
> --- a/drivers/irqchip/irq-mips-cpu.c
> +++ b/drivers/irqchip/irq-mips-cpu.c
> @@ -55,7 +55,6 @@ static struct irq_chip mips_cpu_irq_controller = {
>  	.irq_mask	= mask_mips_irq,
>  	.irq_mask_ack	= mask_mips_irq,
>  	.irq_unmask	= unmask_mips_irq,
> -	.irq_eoi	= unmask_mips_irq,
>  	.irq_disable	= mask_mips_irq,
>  	.irq_enable	= unmask_mips_irq,
>  };

This one scares me; something doesn't seem right. The irq_eoi (née eoi)
callback was first added way back in commit 1417836e81c0 ("[MIPS] use
generic_handle_irq, handle_level_irq, handle_percpu_irq"). The commit
message there states that the motivation was to allow use of
handle_percpu_irq(), and indeed handle_percpu_irq() does:

    irq_ack() (ie. mask)
    invoke the handler(s)
    irq_eoi() (ie. unmask)

By removing the irq_eoi callback I don't see how we'd ever unmask the
interrupt again..?

Thanks,
    Paul

  reply	other threads:[~2020-01-14 23:30 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-13 10:12 Jiaxun Yang
2020-01-14 23:30 ` Paul Burton [this message]
2020-01-15  0:03   ` Jiaxun Yang
2020-01-15 13:40   ` Marc Zyngier
2020-01-15 14:23     ` Jiaxun Yang
2020-01-15 15:22       ` Marc Zyngier
2020-01-17  0:17 ` [PATCH v1 1/2] genirq: Check for level based percpu irq Jiaxun Yang
2020-01-17  0:17   ` [PATCH v1 2/2] irqchip: mips-cpu: Drop unnecessary ack/eoi operations Jiaxun Yang
2020-01-17  1:29   ` [PATCH v1 1/2] genirq: Check for level based percpu irq Thomas Gleixner
2020-01-17  2:23     ` Jiaxun Yang

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