linux-kernel - Re: [PATCH] irqchip: mips-cpu: Remove eoi operation

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Message-ID: <8AEFA134-76BC-4AE9-9229-718B5C58B862@flygoat.com>
Date:   Wed, 15 Jan 2020 08:03:45 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     Paul Burton <paulburton@...nel.org>
CC:     linux-mips@...r.kernel.org, chenhc@...ote.com,
        paul.burton@...s.com, tglx@...utronix.de, jason@...edaemon.net,
        maz@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] irqchip: mips-cpu: Remove eoi operation



于 2020年1月15日 GMT+08:00 上午7:30:25, Paul Burton <paulburton@...nel.org> 写到:
>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@...goat.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..?

Hi Paul,
Sorry I didn't discover that by myself as all of my drivers are using chained handler.

So how should we deal with the chained case?
Probably we need a check in percpu IRQ handler to determine whether it's or not
level type?

>
>Thanks,
>    Paul

-- 
Jiaxun Yang