From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 9 Dec 2002 07:27:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 9 Dec 2002 07:27:05 -0500 Received: from nat-pool-rdu.redhat.com ([66.187.233.200]:42046 "EHLO devserv.devel.redhat.com") by vger.kernel.org with ESMTP id ; Mon, 9 Dec 2002 07:27:04 -0500 Date: Mon, 9 Dec 2002 07:34:34 -0500 From: Arjan van de Ven To: george anzinger Cc: Arjan van de Ven , Linus Torvalds , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/3] High-res-timers part 1 (core) take 20 Message-ID: <20021209073434.A24382@devserv.devel.redhat.com> References: <3DF2F8D9.6CA4DC85@mvista.com> <1039341009.1483.3.camel@laptop.fenrus.com> <3DF44031.58A12F66@mvista.com> <20021209035347.C12524@devserv.devel.redhat.com> <3DF48C4C.3F056661@mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <3DF48C4C.3F056661@mvista.com>; from george@mvista.com on Mon, Dec 09, 2002 at 04:27:56AM -0800 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 09, 2002 at 04:27:56AM -0800, george anzinger wrote: > > > > that's why spinlocks are effectively nops on UP. > > What you say is true of just about every spinlock user, and no > > they shouldn't all do some IF_SMP() thing; the spinlock itself should be > > (and is) zero on UP > > But with preemption, they really are not nops on UP... that doesn't justify fuglyfying the kernel code. If you can't live with the overhead of preemption, disable preemption. Simple. We DON'T want spin_lock_nop_on_preempt() ... spin_unlock_nop_on_preempt() really, I don't, and I can't see anyone else wanting that either