From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753802AbaCZLnn (ORCPT ); Wed, 26 Mar 2014 07:43:43 -0400 Received: from e28smtp09.in.ibm.com ([122.248.162.9]:50029 "EHLO e28smtp09.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751147AbaCZLnf (ORCPT ); Wed, 26 Mar 2014 07:43:35 -0400 Message-ID: <5332BD50.1070600@linux.vnet.ibm.com> Date: Wed, 26 Mar 2014 17:13:12 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: Viresh Kumar CC: tglx@linutronix.de, linaro-kernel@lists.linaro.org, linux-kernel@vger.kernel.org, fweisbec@gmail.com, linaro-networking@linaro.org Subject: Re: [PATCH 04/14] hrtimer: use base->index instead of basenum in switch_hrtimer_base() References: <535a552cd2c05a3ae2cb61da2583646e1c649699.1395832156.git.viresh.kumar@linaro.org> In-Reply-To: <535a552cd2c05a3ae2cb61da2583646e1c649699.1395832156.git.viresh.kumar@linaro.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14032611-2674-0000-0000-00000D5817AC Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/26/2014 04:51 PM, Viresh Kumar wrote: > In switch_hrtimer_base() we have created a local variable basenum which is set > to base->index. This variable is used at only one place. It makes code more > readable if we remove this variable use base->index directly. > No, this doesn't look right. Note that the code can re-execute the assignment to new_base, by jumping to the 'again' label. See below. > --- a/kernel/hrtimer.c > +++ b/kernel/hrtimer.c > @@ -202,11 +202,10 @@ switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base, > struct hrtimer_cpu_base *new_cpu_base; > int this_cpu = smp_processor_id(); > int cpu = get_nohz_timer_target(pinned); > - int basenum = base->index; > > again: > new_cpu_base = &per_cpu(hrtimer_bases, cpu); > - new_base = &new_cpu_base->clock_base[basenum]; > + new_base = &new_cpu_base->clock_base[base->index]; > Further down, timer->base can be altered (and set to NULL too). So if we jump back to 'again', we'll end up in trouble. So I think its important to cache the value in basenum and use it. > if (base != new_base) { > /* > Regards, Srivatsa S. Bhat