linux-kernel - Re: [PATCH 1/11] Add generic helpers for arch IPI function calls

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Date:	Fri, 25 Apr 2008 09:18:24 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	npiggin@...e.de, torvalds@...ux-foundation.org,
	peterz@...radead.org, sam@...nborg.org
Subject: Re: [PATCH 1/11] Add generic helpers for arch IPI function calls

On Thu, Apr 24 2008, Russell King wrote:
> On Tue, Apr 22, 2008 at 08:50:17PM +0200, Jens Axboe wrote:
> > +		data->csd.func(data->csd.info);
> > +
> > +		spin_lock(&data->lock);
> > +		cpu_clear(cpu, data->cpumask);
> > +		WARN_ON(data->refs == 0);
> > +		data->refs--;
> > +		refs = data->refs;
> 
> Probably a silly question, but what does data->refs do that
> cpus_empty(data->cpumask) wouldn't do?  (as indeed ARM presently does.)

I guess it can be marginally slower for NR_CPUS > BITS_PER_LONG,
otherwise there's absolutely no reason to have a seperate ref counter.

-- 
Jens Axboe

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