linux-kernel - Re: [PATCH v3 2/2] irqchip: dw-apb-ictl: add irq_set

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Date:	Mon, 6 Jul 2015 15:51:28 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jisheng Zhang <jszhang@...vell.com>
cc:	jason@...edaemon.net, linux@....linux.org.uk,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 2/2] irqchip: dw-apb-ictl: add irq_set_affinity
 support

On Mon, 6 Jul 2015, Jisheng Zhang wrote:
> On Mon, 6 Jul 2015 12:30:01 +0200
> Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> > On Mon, 6 Jul 2015, Jisheng Zhang wrote:
> > > +static int dw_apb_ictl_set_affinity(struct irq_data *d,
> > > +				    const struct cpumask *mask_val,
> > > +				    bool force)
> > > +{
> > > +	struct irq_chip_generic *gc = irq_data_get_irq_chip_data(d);
> > > +	struct dw_apb_ictl_priv *priv = gc->private;
> > > +	struct irq_chip *chip = irq_get_chip(priv->parent_irq);
> > > +	struct irq_data *data = irq_get_irq_data(priv->parent_irq);
> > > +
> > > +	if (chip && chip->irq_set_affinity)
> > > +		return chip->irq_set_affinity(data, mask_val, force);
> > 
> > This is wrong as it lacks proper locking of the parent irq. That needs
> > to be solved at the core code level in a clean way.
> 
> Is it acceptable to call irq_set_affinity() or irq_force_affinity() as the
> following:
> 
> if (force)
> 	return irq_force_affinity(priv->parent_irq, mask_val);
> else
> 	return irq_set_affinity(priv->parent_irq, mask_val);

Not from the driver, as you run into lock nesting hell. As I said,
this needs to be solved at the core code level and needs a proper
thought out design.

Just for the record: I'm not too happy about that 'fiddle with the
parent' mechanism because it opens just a large can of worms. I wish
hardware designers would talk to OS people before they implement random
nonsense.

Thanks,

	tglx


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