Re: [PATCH 1/1] irq: Maintain user set affinity

[Kumar Gala]

On Nov 6, 2008, at 3:35 PM, Andrew Morton wrote:

> On Tue, 4 Nov 2008 10:31:05 -0600 (CST)
> Kumar Gala <galak@xxxxxxxxxxxxxxxxxxx> wrote:
>
> > > From 819ad3ed4660f4238e053728a8b5aa93d22b13d7 Mon Sep 17 00:00:00  
> > > 2001
> > From: Kumar Gala <galak@xxxxxxxxxxxxxxxxxxx>
> > Date: Tue, 4 Nov 2008 10:13:53 -0600
> > Subject: [PATCH 1/1] irq: Maintain user set affinity
> >
> > This addresses a regression in that if a user specified an affinity
> > for an interrupt that affinity information would get reset between
> > a request_irq(), free_irq() and request_irq() for the same irq.
> >
> > On example of this is bringing up an ethernet interface, taking
> > it down and bringing it back up again.
> >
> > Instead of always using the irq_default_affinity we use the
> > previous setting of the IRQs affinity with the assumption that
> > at boot the IRQs affinity will be set to irq_default_affinity.
> >
> > Signed-off-by: Kumar Gala <galak@xxxxxxxxxxxxxxxxxxx>
> > ---
> > kernel/irq/manage.c |    7 +++++--
> > 1 files changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> > index c498a1b..ea7d11b 100644
> > --- a/kernel/irq/manage.c
> > +++ b/kernel/irq/manage.c
> > @@ -115,9 +115,12 @@ int irq_select_affinity(unsigned int irq)
> > 	if (!irq_can_set_affinity(irq))
> > 		return 0;
> >
> > -	cpus_and(mask, cpu_online_map, irq_default_affinity);
> > -
> > 	desc = irq_to_desc(irq);
> > +
> > +	mask = desc->affinity;
> > +
> > +	cpus_and(mask, cpu_online_map, mask);
> > +
> > 	desc->affinity = mask;
> > 	desc->chip->set_affinity(irq, mask);
>
> Are you able to identify when this regression occurred?  It isn't
> immediately obvious to me.
>
> If the regression is present in 2.6.27 or earlier, do you think we
> should backport the fix?  If so, a different patch would be needed due
> to the presence of
>
> commit 08678b0841267c1d00d771fe01548d86043d065e
> Author: Yinghai Lu <yhlu.kernel@xxxxxxxxx>
> Date:   Tue Aug 19 20:50:05 2008 -0700
>
>    generic: sparse irqs: use irq_desc() together with dyn_array,  
> instead of irq_desc[]

It didn't creep in during 2.6.27.  I will back port a patch to  
2.6.27.  Thomas has provided me a better patch that handles a few  
critical issues that mine doesn't.  I'll be testing it this evening  
and will backport to 2.6.27 if it works out.

- k
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