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Date: Tue, 22 Apr 2008 16:56:10 +0200
From: Eric Dumazet <dada1@cosmosbay.com>
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To: Andrea Arcangeli <andrea@qumranet.com>
Cc: Christoph Lameter <clameter@sgi.com>, Nick Piggin <npiggin@suse.de>,
       Jack Steiner <steiner@sgi.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
       kvm-devel@lists.sourceforge.net, Kanoj Sarcar <kanojsarcar@yahoo.com>,
       Roland Dreier <rdreier@cisco.com>,
       Steve Wise <swise@opengridcomputing.com>, linux-kernel@vger.kernel.org,
       Avi Kivity <avi@qumranet.com>, linux-mm@kvack.org,
       Robin Holt <holt@sgi.com>, general@lists.openfabrics.org,
       Hugh Dickins <hugh@veritas.com>, akpm@linux-foundation.org,
       Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: [PATCH 01 of 12] Core of mmu notifiers
References: <ea87c15371b1bd49380c.1208872277@duo.random>
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Andrea Arcangeli a écrit :
> +
> +static int mm_lock_cmp(const void *a, const void *b)
> +{
> +	cond_resched();
> +	if ((unsigned long)*(spinlock_t **)a <
> +	    (unsigned long)*(spinlock_t **)b)
> +		return -1;
> +	else if (a == b)
> +		return 0;
> +	else
> +		return 1;
> +}
> +
This compare function looks unusual...
It should work, but sort() could be faster if the
if (a == b) test had a chance to be true eventually...

static int mm_lock_cmp(const void *a, const void *b)
{
	unsigned long la = (unsigned long)*(spinlock_t **)a;
	unsigned long lb = (unsigned long)*(spinlock_t **)b;

	cond_resched();
	if (la < lb)
		return -1;
	if (la > lb)
		return 1;
	return 0;
}