Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2992719AbWJTV2T (ORCPT ); Fri, 20 Oct 2006 17:28:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S2992725AbWJTV2T (ORCPT ); Fri, 20 Oct 2006 17:28:19 -0400 Received: from caramon.arm.linux.org.uk ([217.147.92.249]:49934 "EHLO caramon.arm.linux.org.uk") by vger.kernel.org with ESMTP id S2992719AbWJTV2S (ORCPT ); Fri, 20 Oct 2006 17:28:18 -0400 Date: Fri, 20 Oct 2006 22:28:05 +0100 From: Russell King To: Linus Torvalds Cc: David Miller , nickpiggin@yahoo.com.au, ralf@linux-mips.org, Andrew Morton , Linux Kernel Mailing List , anemo@mba.ocn.ne.jp, linux-arch@vger.kernel.org, Martin Schwidefsky Subject: Re: [PATCH 1/3] Fix COW D-cache aliasing on fork Message-ID: <20061020212805.GG8894@flint.arm.linux.org.uk> Mail-Followup-To: Linus Torvalds , David Miller , nickpiggin@yahoo.com.au, ralf@linux-mips.org, Andrew Morton , Linux Kernel Mailing List , anemo@mba.ocn.ne.jp, linux-arch@vger.kernel.org, Martin Schwidefsky References: <20061020.123635.95058911.davem@davemloft.net> <20061020.125851.115909797.davem@davemloft.net> <20061020205929.GE8894@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1155 Lines: 24 On Fri, Oct 20, 2006 at 02:12:11PM -0700, Linus Torvalds wrote: > On Fri, 20 Oct 2006, Russell King wrote: > > Well, looking at do_wp_page() I'm now quite concerned about ARM and COW. > > I can't see how this code could _possibly_ work with a virtually indexed > > cache as it stands. Yet, the kernel does appear to work. > > It really shouldn't need any extra code, exactly because by the time it > hits any page-fault, the caches had better be in sync with the physical > page contents _anyway_ (yes, being virtual, the caches will _duplicate_ > the contents, but since the pages are read-only, that aliasing should be > perfectly fine). Oh, of course! That explains why it actually works as expected! Thanks for filling back in that bit of swapped-out-years-ago-and-lost information. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 Serial core - 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/