Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 9 Dec 2000 10:46:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 9 Dec 2000 10:46:49 -0500 Received: from pizda.ninka.net ([216.101.162.242]:32393 "EHLO pizda.ninka.net") by vger.kernel.org with ESMTP id ; Sat, 9 Dec 2000 10:46:41 -0500 Date: Sat, 9 Dec 2000 07:00:19 -0800 Message-Id: <200012091500.HAA20614@pizda.ninka.net> From: "David S. Miller" To: kernel@tekno-soft.it CC: rasmus@jaquet.dk, torvalds@transmeta.com, linux-kernel@vger.kernel.org In-Reply-To: <4.3.2.7.2.20001209160215.00c901e0@mail.tekno-soft.it> (message from Roberto Fichera on Sat, 09 Dec 2000 16:07:03 +0100) Subject: Re: [PATCH] mm->rss is modified without page_table_lock held In-Reply-To: <4.3.2.7.2.20001209152806.00c8e7b0@mail.tekno-soft.it> <4.3.2.7.2.20001209111347.00c829f0@mail.tekno-soft.it> <4.3.2.7.2.20001209111347.00c829f0@mail.tekno-soft.it> <4.3.2.7.2.20001209152806.00c8e7b0@mail.tekno-soft.it> <4.3.2.7.2.20001209160215.00c901e0@mail.tekno-soft.it> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Date: Sat, 09 Dec 2000 16:07:03 +0100 From: Roberto Fichera 8 bits for a spinlock ? What kind of use we have here ? Sparc32 (like some other older architectures) do not have a word atomic update instruction, but it does have a byte spinlock. To conserve space and implement the atomic update properly, we use a spinlock in the top byte of the word. All arch except Sparc32 don't have this trick. This may not be true forever. Also, this sematic was decided upon many eons ago, changing it a month before 2.4.0 just to deal with this mm->rss atomicity issue is not going to happen. The spinlock patch exists, and if nothing better comes up, we should just use it. Later, David S. Miller davem@redhat.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/