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

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Date:   Mon, 6 Mar 2017 19:05:39 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
cc:     linux-kernel@...r.kernel.org, patches@...nsource.wolfsonmicro.com
Subject: Re: [PATCH] genirq: Fix handling of nested shared IRQs

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,

	tglx