linux-kernel - Re: [PATCH] genirq: Skip chained interrupt trigger configuration if type is IRQ_TYPE

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Message-ID: <57DFADB9.4080806@arm.com>
Date:   Mon, 19 Sep 2016 10:19:53 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH] genirq: Skip chained interrupt trigger configuration if
 type is IRQ_TYPE_NONE

On 19/09/16 10:12, Thomas Gleixner wrote:
> On Mon, 19 Sep 2016, Marc Zyngier wrote:
>> There is no point in trying to configure the trigger of a chained
>> interrupt if no trigger information has been configured. At best
>> this is ignored, and at the worse this confuses the underlying
>> irqchip (which is likely not to handle such a thing), and
>> unnecessarily alarms the user.
>>
>> Only apply the configuration if type is not IRQ_TYPE_NONE.
>>
>> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>> Fixes: 1e12c4a9393b ("genirq: Correctly configure the trigger on chained interrupts")
>> Link: https://lkml.kernel.org/r/CAMuHMdVW1eTn20=EtYcJ8hkVwohaSuH_yQXrY2MGBEvZ8fpFOg@mail.gmail.com
>> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
>> ---
>>  kernel/irq/chip.c | 8 ++++++--
>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
>> index 6373890..26ba565 100644
>> --- a/kernel/irq/chip.c
>> +++ b/kernel/irq/chip.c
>> @@ -820,6 +820,8 @@ __irq_do_set_handler(struct irq_desc *desc, irq_flow_handler_t handle,
>>  	desc->name = name;
>>  
>>  	if (handle != handle_bad_irq && is_chained) {
>> +		unsigned int type = irqd_get_trigger_type(&desc->irq_data);
>> +
>>  		/*
>>  		 * We're about to start this interrupt immediately,
>>  		 * hence the need to set the trigger configuration.
>> @@ -828,8 +830,10 @@ __irq_do_set_handler(struct irq_desc *desc, irq_flow_handler_t handle,
>>  		 * chained interrupt. Reset it immediately because we
>>  		 * do know better.
>>  		 */
>> -		__irq_set_trigger(desc, irqd_get_trigger_type(&desc->irq_data));
>> -		desc->handle_irq = handle;
>> +		if (type != IRQ_TYPE_NONE) {
>> +			__irq_set_trigger(desc, type);
>> +			desc->handle_irq = handle;
> 
> Are you really sure that the handler should only be set when the trigger
> type is != NONE? I seriously doubt that this is correct.

The handler has already been set outside of if() statement (at line
819). Here, we only set it again if we've actually called
__irq_set_trigger() which could have changed it to something that takes
the type into account (handle_level_irq or handle_edge_irq, for example).

Thanks,

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