[RFC patch 7/8] genirq: generic chip: Add linear irq domain support

Thomas Gleixner
2013-05-03T22:38:34Z

On Fri, 3 May 2013, Russell King - ARM Linux wrote:

> On Fri, May 03, 2013 at 09:50:53PM -0000, Thomas Gleixner wrote:
> > + /* Init mask cache ? */
> > + if (dgc->gc_flags & IRQ_GC_INIT_MASK_CACHE) {
> > + raw_spin_lock_irqsave(&gc->lock, flags);
> > + gc->mask_cache = irq_reg_readl(gc->reg_base + ct->regs.mask);
> > + raw_spin_unlock_irqrestore(&gc->lock, flags);
> > + }
>
> This looks a little weird to me - it seems that it'll re-read this
> each time any irq is mapped in the domain, which is probably not
> wanted.

Yes, it's sloppy in two aspects.

1) It does not respect the per irq type mask cache, which got
introduced in the same series

2) It rereads the mask cache for each mapping, but thats harmless
because it's proper serialized. We can avoid that by clearing the
IRQ_GC_INIT_MASK_CACHE bit when the first irq of that chip is
mapped.

Congrats, you found a bug and as I said:

WARNING: It's compile tested only. So if you find bugs you can keep
them and fix them yourself :)

Thanks,

tglx