linux-kernel - Re: [PATCH] genirq: Fix handling of nested shared IRQs

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Date:   Tue, 7 Mar 2017 09:15:06 +0000
From:   Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
To:     Thomas Gleixner <tglx@...utronix.de>
CC:     <linux-kernel@...r.kernel.org>,
        <patches@...nsource.wolfsonmicro.com>
Subject: Re: [PATCH] genirq: Fix handling of nested shared IRQs

On Mon, Mar 06, 2017 at 07:05:39PM +0100, Thomas Gleixner wrote:
> On Mon, 6 Mar 2017, Charles Keepax wrote:
> 
> > When an IRQ is nested the nested handler is called directly from within the
> > threaded handler of the parent IRQ, however, the code in handle_nested_irq
> > only calls a single handler. This means when a shared IRQ is nested only
> > the first of the shared IRQ handlers will be run. This patch adds a loop
> > to move through and process all the handlers associated with the IRQ in
> > handle_nested_irq.
> 
> That was never meant to deal with nested shaed interrupts, so the $subject
> is misleading. This is not a fix, it's a functional extension.
> 
> Aside of that, please structure the changelog in paragraphs instead of one
> big lump.
> 
>  1) Context
>  2) Problem
>  3) Solution
> 
> See also Documentation/process/submitting-patches.rst and please search
> there for "This patch" .....
> 
> > @@ -348,9 +348,12 @@ void handle_nested_irq(unsigned int irq)
> >  	irqd_set(&desc->irq_data, IRQD_IRQ_INPROGRESS);
> >  	raw_spin_unlock_irq(&desc->lock);
> >  
> > -	action_ret = action->thread_fn(action->irq, action->dev_id);
> > -	if (!noirqdebug)
> > -		note_interrupt(desc, action_ret);
> > +	do {
> 
>   	for_each_action_of_desc() please
> 
> > +		action_ret = action->thread_fn(action->irq, action->dev_id);
> > +		if (!noirqdebug)
> > +			note_interrupt(desc, action_ret);
> 
> That's wrong. See __handle_irq_event_percpu() for the correct handling of
> shared interrupts vs. note_interrupt() 
> 

Thanks for the pointers, I will look at those and respin the
patch.

Thanks,
Charles