Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937337AbWLFT0g (ORCPT ); Wed, 6 Dec 2006 14:26:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S937442AbWLFT0f (ORCPT ); Wed, 6 Dec 2006 14:26:35 -0500 Received: from smtp.osdl.org ([65.172.181.25]:60110 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937337AbWLFT0e (ORCPT ); Wed, 6 Dec 2006 14:26:34 -0500 Date: Wed, 6 Dec 2006 11:25:35 -0800 (PST) From: Linus Torvalds To: Al Viro cc: Christoph Lameter , Russell King , David Howells , Andrew Morton , linux-arm-kernel@lists.arm.linux.org.uk, Linux Kernel Mailing List , linux-arch@vger.kernel.org Subject: Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it In-Reply-To: <20061206190828.GE4587@ftp.linux.org.uk> Message-ID: References: <20061206164314.19870.33519.stgit@warthog.cambridge.redhat.com> <20061206190828.GE4587@ftp.linux.org.uk> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 768 Lines: 21 On Wed, 6 Dec 2006, Al Viro wrote: > > No. sparc32 doesn't have one, for instance. Ok. For SMP-safety, it's important that any architecture that can't do this needs to _share_ the same spinlock (on SMP only, of course) that it uses for the bitops. It would be good (but perhaps not as strict a requirement) if the atomic counters also use the same lock. But that is probably impossible on sparc32 (since it has a per-counter "lock"-like thing, iirc). So doing a cmpxchg() on an atomic_t would be a bug. Linus - 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/