Re: [PATCH-v5 1/6] idr: Percpu ida

Nicholas A. Bellinger
2013-09-04T04:34:56Z

On Tue, 2013-09-03 at 18:27 -0700, Andrew Morton wrote:
> On Tue, 03 Sep 2013 09:06:58 -0700 "Nicholas A. Bellinger" <nab@linux-iscsi.org> wrote:
>
> > Are there any other review comments to be addressed for this patch..?
> >
> > If not, please kindly give your Reviewed-by if your OK for an initial
> > standalone merge.
>
> Sorry, I'm largely offline for the next week...
>
> It looks OK to me (that's as close as I get to an ack :))
>

Thanks. That quote is going in the commit log btw. ;)

> Nit:
>
> > + if (cpu >= nr_cpu_ids)
> > + cpu = cpumask_first(&pool->cpus_have_tags);
> > +
> > + if (cpu >= nr_cpu_ids)
> > + BUG();
>
> The second `if' can be moved inside the first, but hopefully the
> compiler already did that.

Fixed.

>
> I have dim memories that doing
>
> local_irq_save()
> spin_lock()
>
> is not equivalent to
>
> spin_lock_irqsave()
>
> in some circumstances. Perhaps a lockdep thing. Or perhaps this was fixed in
> the intervening years and this is no longer the case.

Mmmm, I had wondered the same thing on the release side with
kref_put_spinlock_irqsave() here before:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/include/linux/kref.h?id=ccf5ae83a6cf3d9cfe9a7038bfe7cd38ab03d5e1

but at some point was convinced it was not a issue anymore..

>
> Such things probably won't be detected during 3.12-rcX because few
> people will test iscsi, I expect. So please be sure that you've
> runtime tested it with all the lockdeppy things enabled.
> Documentation/SubmitChecklist section 12 has a list, but it might be
> dated.

<nod>

FYI, my v3.11-rc5 kernel has been running with CONFIG_LOCKDEP_SUPPORT=y
using vhost/iscsi/iser fabrics on the -v5 patch, and not generated any
warnings (yet).

I'll double check against the other debug options in Section 12.

Thank you,

--nab