Re: [tip:irq/genirq] irq: refactor and clean up the free_irq()code flow

[Ingo Molnar]

* Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Sun, 15 Feb 2009, Ingo Molnar wrote:
> >  	struct irq_desc *desc = irq_to_desc(irq);
> > -	struct irqaction **p;
> > +	struct irqaction *action, **p, **pp;
> 
> The whole reason for 'pp' seems to be the confusing loop:
> 
> >  	for (;;) {
> > +		action = *p;
> > +		pp = p;
> > +
> > +		if (!action) {
> > +			WARN(1, "Trying to free already-free IRQ %d\n", irq);
> > +			spin_unlock_irqrestore(&desc->lock, flags);
> > +
> > +			return;
> > +		}
> >  
> > +		p = &action->next;
> > +		if (action->dev_id != dev_id)
> > +			continue;
> >  
> > +		break;
> > +	}
> > +	/* Found it - now remove it from the list of entries: */
> > +	*pp = action->next;
> 
> Where the need for 'pp' would go away if you'd just write it as
> 
> 		if (action->dev_id == dev_id)
> 			break;
> 		p = &action->next;
> 	}
> 	*p = action->next;
> 
> instead. Which also makes it both shorter and more readable.

Ah, good point. I concentrated on an identity transformation 
primarily and missed that simplification.

Something like the patch below? (plus the followup cleanup 
further below?)

	Ingo

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