Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937714AbWLFWFg (ORCPT ); Wed, 6 Dec 2006 17:05:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S937707AbWLFWFf (ORCPT ); Wed, 6 Dec 2006 17:05:35 -0500 Received: from palinux.external.hp.com ([192.25.206.14]:54471 "EHLO mail.parisc-linux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937705AbWLFWFd (ORCPT ); Wed, 6 Dec 2006 17:05:33 -0500 Date: Wed, 6 Dec 2006 15:05:32 -0700 From: Matthew Wilcox To: Christoph Lameter Cc: David Howells , torvalds@osdl.org, akpm@osdl.org, linux-arm-kernel@lists.arm.linux.org.uk, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it Message-ID: <20061206220532.GF3013@parisc-linux.org> References: <20061206164314.19870.33519.stgit@warthog.cambridge.redhat.com> <20061206190025.GC9959@flint.arm.linux.org.uk> <20061206195820.GA15281@flint.arm.linux.org.uk> <20061206213626.GE3013@parisc-linux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1029 Lines: 26 On Wed, Dec 06, 2006 at 01:52:20PM -0800, Christoph Lameter wrote: > On Wed, 6 Dec 2006, Matthew Wilcox wrote: > > > And for those of us with only load-and-zero, that's simply: > > > > #define load_locked(addr) spin_lock(hash(addr)), *addr > > #define store_exclusive(addr, old, new) \ > > *addr = new, spin_unlock(hash(addr)), 0 > > > > which is also optimal for us. > > This means we tolerate the assignment race for SMP that was pointed out > earlier? What gave you that impression? It simply wasn't part of this example. To be honest, it'd be much easier if we only defined these operations on atomic_t's. We have all the infrastructure in place for them, and they're fairly well understood. If you need different sizes, I'm OK with an atomic_pointer_t, or whatever. - 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/