Re: [PATCH v2] genirq: Check irq disabled & masked states in irq_shutdown

[jeffy]

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