From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754486AbaCZMkb (ORCPT ); Wed, 26 Mar 2014 08:40:31 -0400 Received: from e28smtp07.in.ibm.com ([122.248.162.7]:35396 "EHLO e28smtp07.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753743AbaCZMka (ORCPT ); Wed, 26 Mar 2014 08:40:30 -0400 Message-ID: <5332CAA7.8000901@linux.vnet.ibm.com> Date: Wed, 26 Mar 2014 18:10:07 +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 12/14] hrtimer: don't emulate notifier call to initialize timer base References: <7eb4d1a03031b4d873ce08e8912900d7936a3ca8.1395832156.git.viresh.kumar@linaro.org> In-Reply-To: <7eb4d1a03031b4d873ce08e8912900d7936a3ca8.1395832156.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: 14032612-8878-0000-0000-00000B7FAA11 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 hrtimers_init() we need to call init_hrtimers_cpu() for boot CPU. For this, > currently we are emulating a call to hotplug notifier. Probably this was done > initially to get rid of code redundancy. But this sequence always called a > single routine, i.e. init_hrtimers_cpu(), and so calling that routine directly > would be better. This would get rid of emulating a notifier call, few typecasts > and the extra steps we are doing in notifier callback. > > So, this patch calls init_hrtimers_cpu() directly from hrtimers_init(). > I don't think this is such a good idea. Open-coding a part of that callback in the init routine can lead to loop-holes down the road: what if someone changes or adds something to the CPU_UP_PREPARE switch-case, and forgets to do the same in the init-routine? It is more comforting to know that there is just one single place where CPU hotplug operations are handled (hrtimer_cpu_notify). That, in turn is good for reliability because it makes it easier to write bug-free code. Regards, Srivatsa S. Bhat > Signed-off-by: Viresh Kumar > --- > kernel/hrtimer.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c > index f14d861..39dbdbd 100644 > --- a/kernel/hrtimer.c > +++ b/kernel/hrtimer.c > @@ -1756,8 +1756,7 @@ static struct notifier_block hrtimers_nb = { > > void __init hrtimers_init(void) > { > - hrtimer_cpu_notify(&hrtimers_nb, (unsigned long)CPU_UP_PREPARE, > - (void *)(long)smp_processor_id()); > + init_hrtimers_cpu(smp_processor_id()); > register_cpu_notifier(&hrtimers_nb); > #ifdef CONFIG_HIGH_RES_TIMERS > open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq); >