From mboxrd@z Thu Jan  1 00:00:00 1970
From: tglx@linutronix.de (Thomas Gleixner)
Date: Mon, 6 Jul 2015 15:51:28 +0200 (CEST)
Subject: [PATCH v3 2/2] irqchip: dw-apb-ictl: add irq_set_affinity support
In-Reply-To: <20150706211035.6676916f@xhacker>
References: <1436156141-3674-1-git-send-email-jszhang@marvell.com>
 <1436156141-3674-3-git-send-email-jszhang@marvell.com>
 <alpine.DEB.2.11.1507061228060.3916@nanos> <20150706211035.6676916f@xhacker>
Message-ID: <alpine.DEB.2.11.1507061524350.3916@nanos>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Mon, 6 Jul 2015, Jisheng Zhang wrote:
> On Mon, 6 Jul 2015 12:30:01 +0200
> Thomas Gleixner <tglx@linutronix.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