From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754164AbYAQBxZ (ORCPT ); Wed, 16 Jan 2008 20:53:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751384AbYAQBxQ (ORCPT ); Wed, 16 Jan 2008 20:53:16 -0500 Received: from tomts5-srv.bellnexxia.net ([209.226.175.25]:47543 "EHLO tomts5-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751348AbYAQBxP (ORCPT ); Wed, 16 Jan 2008 20:53:15 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Aq4HAM5DjkdMROHU/2dsb2JhbACBWKxK Date: Wed, 16 Jan 2008 20:48:13 -0500 From: Mathieu Desnoyers To: Li Zefan Cc: Andrew Morton , LKML Subject: Re: [PATCH] Revert "local_t Documentation update" Message-ID: <20080117014813.GA2322@Krystal> References: <478EB2CC.8000900@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <478EB2CC.8000900@cn.fujitsu.com> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 20:47:34 up 74 days, 6:53, 5 users, load average: 0.12, 0.38, 0.47 User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Li Zefan (lizf@cn.fujitsu.com) wrote: > This reverts commit e1265205c0ee3919c3f2c750662630154c8faab2. > > It's a duplicate commit of commit 74beb9db77930be476b267ec8518a642f39a04bf, > resulting in a duplicate section. > > Signed-off-by: Li Zefan > Thanks, I guess it's been merged twice somehow :S Acked-by: Mathieu Desnoyers > --- > Documentation/local_ops.txt | 23 ----------------------- > 1 files changed, 0 insertions(+), 23 deletions(-) > > diff --git a/Documentation/local_ops.txt b/Documentation/local_ops.txt > index 1a45f11..4269a11 100644 > --- a/Documentation/local_ops.txt > +++ b/Documentation/local_ops.txt > @@ -68,29 +68,6 @@ typedef struct { atomic_long_t a; } local_t; > variable can be read when reading some _other_ cpu's variables. > > > -* Rules to follow when using local atomic operations > - > -- Variables touched by local ops must be per cpu variables. > -- _Only_ the CPU owner of these variables must write to them. > -- This CPU can use local ops from any context (process, irq, softirq, nmi, ...) > - to update its local_t variables. > -- Preemption (or interrupts) must be disabled when using local ops in > - process context to make sure the process won't be migrated to a > - different CPU between getting the per-cpu variable and doing the > - actual local op. > -- When using local ops in interrupt context, no special care must be > - taken on a mainline kernel, since they will run on the local CPU with > - preemption already disabled. I suggest, however, to explicitly > - disable preemption anyway to make sure it will still work correctly on > - -rt kernels. > -- Reading the local cpu variable will provide the current copy of the > - variable. > -- Reads of these variables can be done from any CPU, because updates to > - "long", aligned, variables are always atomic. Since no memory > - synchronization is done by the writer CPU, an outdated copy of the > - variable can be read when reading some _other_ cpu's variables. > - > - > * How to use local atomic operations > > #include > -- > 1.5.3.rc7 > -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68