From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753121AbdFVO5c (ORCPT ); Thu, 22 Jun 2017 10:57:32 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:60732 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752370AbdFVOzU (ORCPT ); Thu, 22 Jun 2017 10:55:20 -0400 Date: Thu, 22 Jun 2017 07:55:16 -0700 From: "Paul E. McKenney" To: Ingo Molnar Cc: Arnd Bergmann , Thomas Gleixner , Sebastian Andrzej Siewior , Anna-Maria Gleixner , Boris Ostrovsky , linux-kernel@vger.kernel.org Subject: Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init Reply-To: paulmck@linux.vnet.ibm.com References: <20170621215741.4028236-1-arnd@arndb.de> <20170621221054.GU3721@linux.vnet.ibm.com> <20170622072644.so23jacjhvrox5pd@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170622072644.so23jacjhvrox5pd@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17062214-0008-0000-0000-0000024A5E44 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007272; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000214; SDB=6.00878326; UDB=6.00437634; IPR=6.00658462; BA=6.00005437; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00015925; XFM=3.00000015; UTC=2017-06-22 14:55:17 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17062214-0009-0000-0000-000035C2EA73 Message-Id: <20170622145516.GZ3721@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-06-22_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1706220257 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 22, 2017 at 09:26:44AM +0200, Ingo Molnar wrote: > > * Paul E. McKenney wrote: > > > On Wed, Jun 21, 2017 at 11:57:28PM +0200, Arnd Bergmann wrote: > > > Without CONFIG_SMP, we get a harmless warning about > > > an unused variable: > > > > > > kernel/cpu.c: In function 'boot_cpu_state_init': > > > kernel/cpu.c:1778:6: error: unused variable 'cpu' [-Werror=unused-variable] > > > > > > This reworks the function to have the declaration inside > > > of the #ifdef. > > > > > > Fixes: faeb334286b7 ("rcu: Migrate callbacks earlier in the CPU-offline timeline") > > > Signed-off-by: Arnd Bergmann > > > > I simply added a __maybe_unused in 6441c656acde ("rcu: Migrate callbacks > > earlier in the CPU-offline timeline") in my -rcu tree. However, your > > approach does have the advantage of complaining if the code using that > > variable is removed. > > > > So, would you be OK with my folding your approach into my commit with > > attribution? > > Also, note that __maybe_unused can be dangerous: it can hide a build warning where > there's a _real_ unused variable bug now or due to future changes, causing a real > runtime bug. > > So I think we should consider it a syntactic construct to avoid. I will review the ones in RCU. Thanx, Paul