From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <dada1@cosmosbay.com>
Subject: Re: [PATCH 01 of 12] Core of mmu notifiers
Date: Tue, 22 Apr 2008 16:56:10 +0200
Message-ID: <480DFC8A.8040105@cosmosbay.com>
References: <ea87c15371b1bd49380c.1208872277@duo.random>
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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>
To: Andrea Arcangeli <andrea@qumranet.com>
Return-path: <linux-kernel-owner+glk-linux-kernel-3=40m.gmane.org-S1761169AbYDVO4v@vger.kernel.org>
In-Reply-To: <ea87c15371b1bd49380c.1208872277@duo.random>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

Andrea Arcangeli a =E9crit :
> +
> +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 =3D=3D b)
> +		return 0;
> +	else
> +		return 1;
> +}
> +
This compare function looks unusual...
It should work, but sort() could be faster if the
if (a =3D=3D b) test had a chance to be true eventually...

static int mm_lock_cmp(const void *a, const void *b)
{
	unsigned long la =3D (unsigned long)*(spinlock_t **)a;
	unsigned long lb =3D (unsigned long)*(spinlock_t **)b;

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