From: Andi Kleen Subject: Re: [patch 2/8] Implement always-locked bit ops, for memory shared with an SMP hypervisor. Date: Thu, 3 Aug 2006 06:49:11 +0200 Message-ID: <200608030649.11452.ak@suse.de> References: <20060803002510.634721860@xensource.com> <200608030445.38189.ak@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org To: Christoph Lameter Cc: virtualization@lists.osdl.org, Jeremy Fitzhardinge , akpm@osdl.org, xen-devel@lists.xensource.com, Chris Wright , Ian Pratt , linux-kernel@vger.kernel.org List-Id: xen-devel@lists.xenproject.org On Thursday 03 August 2006 06:27, Christoph Lameter wrote: > On Thu, 3 Aug 2006, Andi Kleen wrote: > > > > > > Thats a good goal but what about the rest of us who have to maintain > > > additional forms of bit operations for all architectures. How much is this > > > burden? > > > > I don't think it's that big an issue because most architectures either > > use always locked bitops already or don't need them because they don't do > > SMP. > > Those architectures that always use locked bitops or dont need them would > not need to be modified if we put this in a special fail. I think this is > a i386 speciality here? i386/x86-64 They could do a single line #include for asm-generic that defines them to the normal bitops. > > Those operations are only needed for special xen driver and not for > regular kernel code! The Xen driver will be "regular" kernel code. > > So it will be fine with just a asm-generic header that defines them > > to the normal bitops. Not much burden. > > asm-generic/xen-bitops.h asm-i386/xen-bitops.h is even less of a burden > and would only require a > > #include > > for those special xen drivers. Well there might be reasons someone else uses this in the future too. It's also not exactly Linux style - normally we try to add generic facilities. -Andi