linux-kernel - Re: [PATCH v2] genirq: Check irq disabled & masked states in irq

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Message-ID: <59295059.7070509@rock-chips.com>
Date:   Sat, 27 May 2017 18:09:29 +0800
From:   jeffy <jeffy.chen@...k-chips.com>
To:     Thomas Gleixner <tglx@...utronix.de>
CC:     linux-kernel@...r.kernel.org, briannorris@...omium.org,
        dianders@...omium.org, tfiga@...omium.org
Subject: Re: [PATCH v2] genirq: Check irq disabled & masked states in irq_shutdown

Hi Thomas,

On 05/27/2017 04:30 PM, Thomas Gleixner wrote:
> On Sat, 27 May 2017, Jeffy Chen wrote:
>
>> If a irq is already disabled & masked, free_irq may cause a unbalanced
>> irq shutdown/disable/mask, for example:
>
> No, it's not. irq_shutdown/disable/mask are low level access functions
> which can be invoked at any given time.
>
> The only interface which has refcounting is disable/enable_irq().
but i think it still be good trying to make them balance, at least for 
irq enable/disable :)
>
>> devm_request_irq->irq_startup->irq_enable
>> disable_irq					<-- disabled and masked
>> devm_free_irq->irq_shutdown			<-- try to disable it again
>>
>> This would confuse some pinctrl drivers which would control clk in
>> irq_enable/irq_disable, for example pinctrl-rockchip/pinctrl-nomadik.
>>
>> This patch add a state check in irq_shutdown to prevent that.
>
> Please read Documentation/process/SubmittingPatches and search for "this
> patch".
oops
>
>> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
>> index 686be4b..816da03 100644
>> --- a/kernel/irq/chip.c
>> +++ b/kernel/irq/chip.c
>> @@ -206,14 +206,20 @@ int irq_startup(struct irq_desc *desc, bool resend)
>>
>>   void irq_shutdown(struct irq_desc *desc)
>>   {
>> -	irq_state_set_disabled(desc);
>>   	desc->depth = 1;
>> +
>> +	if (unlikely(irqd_irq_disabled(&desc->irq_data) &&
>> +		irqd_irq_masked(&desc->irq_data)))
>> +		goto out;
>
> This is just wrong.
>
> It's perfectly legit to call disable_irq() and then free_irq(). Still
> free_irq() has to be able to invoke chip->irq_shutdown(). Preventing that
> will leave some interrupt chips in a half initialized state.
right, irq_shutdown is not just to disable irq, may also do some 
cleanups. will upload new patch.
>
> The irq core does not guarntee that the unmask/mask enable/disable
> startup/shutdown callbacks are perfectly balanced. irq_shutdown() is only
> one place where this can happen. This needs more thought than this 'works
> for me' hackery.
>
> Thanks,
>
> 	tglx
>
>
>