From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock Date: Mon, 19 Apr 2010 14:10:54 +0300 Message-ID: <4BCC3A3E.9070909@redhat.com> References: <1271356648-5108-1-git-send-email-glommer@redhat.com> <1271356648-5108-2-git-send-email-glommer@redhat.com> <4BC8CA52.4090703@goop.org> <1271673545.1674.743.camel@laptop> <4BCC3584.1050501@redhat.com> <1271675100.1674.818.camel@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Jeremy Fitzhardinge , Glauber Costa , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Marcelo Tosatti , Zachary Amsden To: Peter Zijlstra Return-path: In-Reply-To: <1271675100.1674.818.camel@laptop> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 04/19/2010 02:05 PM, Peter Zijlstra wrote: >> >>> ACCESS_ONCE() is your friend. >>> >>> >> I think it's implied with atomic64_read(). >> > Yes it would be. I was merely trying to point out that > > last = ACCESS_ONCE(last_value); > > Is a narrower way of writing: > > last = last_value; > barrier(); > > In that it need not clobber all memory locations and makes it instantly > clear what we want the barrier for. > Oh yes, just trying to avoid a patch with both atomic64_read() and ACCESS_ONCE(). -- error compiling committee.c: too many arguments to function