Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756403Ab1CRIp1 (ORCPT ); Fri, 18 Mar 2011 04:45:27 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:38361 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754687Ab1CRIpU convert rfc822-to-8bit (ORCPT ); Fri, 18 Mar 2011 04:45:20 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type:content-transfer-encoding; b=rubyvgfWvAMLDTgwh+mBfGzCW+komD/EVlIKFGZdaNn+0oDDSNk2FKfQEQKANAcQvc UKChwF2mt1DICKmyaMB9g6PT9BnrPrrVh+Emgxmi8fuGbJQrS8grG9ZXsk+wa76UiSYQ xW/cpIJRs8EGwaRWG2CrCQ2kQkNvQfK78NE4A= MIME-Version: 1.0 In-Reply-To: References: <1300098516-1601-1-git-send-email-ratbert.chuang@gmail.com> <1300169637-1628-1-git-send-email-ratbert.chuang@gmail.com> From: Po-Yu Chuang Date: Fri, 18 Mar 2011 16:44:44 +0800 Message-ID: Subject: Re: [PATCH v2] arm: cmpxchg syscall should data abort if page not write To: Nicolas Pitre Cc: Ashwin Chaugule , Russell King - ARM Linux , Po-Yu Chuang , tony@atomide.com, lkml , joe@perches.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1375 Lines: 34 Dear Nicolas Pitre, On Fri, Mar 18, 2011 at 1:57 AM, Nicolas Pitre wrote: > On Thu, 17 Mar 2011, Ashwin Chaugule wrote: >> >> Just beginning to understand the subtleties involved, so please >> correct me if I'm wrong. >> Wont this patch also fix the problem that was brought up with futexes >> on ARM SMP ? > > Nope.  The code being fixed here was suptly broken so it needs fixing. > However this code is almost never used, if at all, as it is a fall-back > solution for when all the better alternatives are not available for some > reasons (and I'm still wondering what those reasons are for Po-Yu Chuang > to actually use that code).  In practice this bug should have affected > no one. We met this problem while porting an v5 SMP processor because kernel selects NEEDS_SYSCALL_FOR_CMPXCHG by default if CPU_32v5. After we added our own implementation of __kuser_cmpxchg, this code is not needed anymore. But since this is actually a bug, it is still a good idea to submit a patch. :-) > If you have SMP then this code is definitively not what you should be > using. Best regards, Po-Yu Chuang -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/