Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757105AbYCCOoj (ORCPT ); Mon, 3 Mar 2008 09:44:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753742AbYCCOnv (ORCPT ); Mon, 3 Mar 2008 09:43:51 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:37136 "EHLO gprs189-60.eurotel.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753549AbYCCOnt (ORCPT ); Mon, 3 Mar 2008 09:43:49 -0500 Date: Mon, 3 Mar 2008 13:08:42 +0100 From: Pavel Machek To: Alan Stern , Linus Torvalds , Andrew Morton Cc: Zdenek Kabelac , davem@davemloft.net, "Rafael J. Wysocki" , Pierre Ossman , Kernel development list , pm list Subject: [patch] Re: using long instead of atomic_t when only set/read is required Message-ID: <20080303120842.GA28369@elf.ucw.cz> References: <20080225090316.GA420@elf.ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1429 Lines: 40 Hi! > > Alan thinks that `subj` is correct... > > More precisely, reads and writes of pointers are always atomic. That > is, if a write and a read occur concurrently, it is guaranteed that the > read will obtain either the old or the new value of the pointer, never > a mish-mash of the two. If this were not so then RCU wouldn't work. Ok, so linux actually atomicity of long? If so, this should probably be applied... Signed-off-by: Pavel Machek diff --git a/Documentation/atomic_ops.txt b/Documentation/atomic_ops.txt index 4ef2450..0a7d180 100644 --- a/Documentation/atomic_ops.txt +++ b/Documentation/atomic_ops.txt @@ -21,6 +21,9 @@ local_t is very similar to atomic_t. If updated by one CPU, local_t is probably more appropriate. Please see Documentation/local_ops.txt for the semantics of local_t. +long (and int and void *) can be used instead of atomic_t, if all you +need is atomic setting and atomic reading. + The first operations to implement for atomic_t's are the initializers and plain reads. -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/