From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 28 May 2002 20:59:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 28 May 2002 20:59:48 -0400 Received: from gateway-1237.mvista.com ([12.44.186.158]:31735 "EHLO av.mvista.com") by vger.kernel.org with ESMTP id ; Tue, 28 May 2002 20:59:47 -0400 Message-ID: <3CF427E4.79042F@mvista.com> Date: Tue, 28 May 2002 17:59:16 -0700 From: george anzinger Organization: Monta Vista Software X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.2.12-20b i686) X-Accept-Language: en MIME-Version: 1.0 To: Keith Whitwell CC: linux-kernel@vger.kernel.org Subject: Re: linux-2.5.18: DRM + cmpxchg issues In-Reply-To: <3CF33C10.1090302@tungstengraphics.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Keith Whitwell wrote: > > Adam, > > I expect the answer is that we need to dig out the old one. > > Previously I don't think the full cmpxchg semantics werere required unless the > box is smp -- there's no case where atomic operations are required for > hardware interaction, for example. ... > > Probably this changed with preempt, though, so we need one even on UP boxes... > I can not think of any reason to need a lock or atomic operation because of preempt. Even the management of the preempt on/off flags at most requires memory barriers, even in SMP boxen. Do you have an example? -- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Real time sched: http://sourceforge.net/projects/rtsched/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml