From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932469Ab0IGUBH (ORCPT ); Tue, 7 Sep 2010 16:01:07 -0400 Received: from moutng.kundenserver.de ([212.227.126.171]:63984 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932101Ab0IGUBE (ORCPT ); Tue, 7 Sep 2010 16:01:04 -0400 From: Arnd Bergmann To: Kulikov Vasiliy Subject: Re: [PATCH] md: do not use ++ in rcu_dereference() argument Date: Tue, 7 Sep 2010 22:00:58 +0200 User-Agent: KMail/1.13.5 (Linux/2.6.36-rc3; KDE/4.5.1; x86_64; ; ) Cc: "Paul E. McKenney" , kernel-janitors@vger.kernel.org, Neil Brown , Jens Axboe , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org References: <1283711539-7123-1-git-send-email-segooon@gmail.com> <201009062210.56824.arnd@arndb.de> <20100907192154.GA14214@albatros> In-Reply-To: <20100907192154.GA14214@albatros> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201009072200.59509.arnd@arndb.de> X-Provags-ID: V02:K0:8lTfGfAhfWeqMltL6a+1wpVvM7X//vsWBzBU2lgwG/D VXCYLeDGO8VXHN1Z8uhvBqPIxhZitt33Uz9C5HmeNzh6yWzsYp e4jDYo7DyWs59eTNyIgmhTTQs501aBiimq9/oNFxWc7hiz3v8/ ZIIdOdrNARyHalYbRFFGT2crjLZ82+G/jAOic4wB5p+XTsJ6Hr hjEDZN1UpKE0aGRhPIvvg== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 07 September 2010 21:21:55 Kulikov Vasiliy wrote: > #define __rcu_dereference_check(p, c, space) \ > ({ \ > typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ > ^ > rcu_lockdep_assert(c); \ > (void) (((typeof (*p) space *)p) == p); \ > ^ ^ > smp_read_barrier_depends(); \ > ((typeof(*p) __force __kernel *)(_________p1)); \ > }) > > If I understand this, it is evaluated three times, right? Yes, that looks like my own fault, I added that :( This patch seems to fix it, but I need to think about it some more to make sure it still does everything we need. Signed-off-by: Arnd Bergmann diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 89414d6..743bc3f 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -313,21 +313,21 @@ extern int rcu_my_thread_group_empty(void); #define __rcu_access_pointer(p, space) \ ({ \ typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ - (void) (((typeof (*p) space *)p) == p); \ + (void) (((typeof (*p) space *)NULL) == (typeof(p))NULL); \ ((typeof(*p) __force __kernel *)(_________p1)); \ }) #define __rcu_dereference_check(p, c, space) \ ({ \ typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ rcu_lockdep_assert(c); \ - (void) (((typeof (*p) space *)p) == p); \ + (void) (((typeof (*p) space *)NULL) == (typeof(p))NULL); \ smp_read_barrier_depends(); \ ((typeof(*p) __force __kernel *)(_________p1)); \ }) #define __rcu_dereference_protected(p, c, space) \ ({ \ rcu_lockdep_assert(c); \ - (void) (((typeof (*p) space *)p) == p); \ + (void) (((typeof (*p) space *)NULL) == (typeof(p))NULL); \ ((typeof(*p) __force __kernel *)(p)); \ })