* Alexander Gordeev <agordeev@xxxxxxxxxx> wrote:
> On Tue, Oct 02, 2012 at 06:55:18AM +0200, Ingo Molnar wrote:
>
> Thanks for the review, Ingo.
>
> > > @@ -584,8 +586,12 @@ int __irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node,
> > > #define irq_alloc_desc_from(from, node) \
> > > irq_alloc_descs(-1, from, 1, node)
> > >
> > > +#define irq_alloc_descs_from(from, cnt, node) \
> > > + irq_alloc_descs(-1, from, cnt, node)
> > > +
> >
> > Please use inlines instead of macros. Might transform the one
> > above it as well in the process.
>
> You mean here do not introduce irq_alloc_descs_from, but rather use
> irq_alloc_descs() directly?
My suggestion is to add irq_alloc_descs_from() as a (very
simple) inline function and change irq_alloc_desc_from() to be
an inline function as well.
> > > +int irq_can_alloc_irqs(unsigned int from, unsigned int cnt)
> > > +{
> > > + unsigned int start;
> > > + int ret = 0;
> > > +
> > > + if (!cnt)
> > > + return -EINVAL;
> > > +
> > > + mutex_lock(&sparse_irq_lock);
> > > + start = bitmap_find_next_zero_area(allocated_irqs, IRQ_BITMAP_BITS,
> > > + from, cnt, 0);
> > > + mutex_unlock(&sparse_irq_lock);
> > > + if (start + cnt > nr_irqs)
> > > + ret = irq_can_expand_nr_irqs(start + cnt);
> > > + return ret;
> >
> > How is this supposed to work wrt. races?
>
> It is not supposed. Just a quick check if there are enough bits before an
> attempt to allocate memory in __create_irqs(). Otherwise __create_irqs()
> might allocate irq_cfg's, then realize there are no bits, then deallocate
> and fail.
>
> But strictly speaking, irq_can_alloc_irqs() is unnecessary.
Why complicate it if it's unnecessary? The function is inviting
wrong logic: it *cannot* tell whether there are enough bits,
because the check is racy.
So I'd suggest to keep this out - this will further simplify the
patches.
Thanks,
Ingo
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