Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751272AbaDODz7 (ORCPT ); Mon, 14 Apr 2014 23:55:59 -0400 Received: from mail-ob0-f181.google.com ([209.85.214.181]:37725 "EHLO mail-ob0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750873AbaDODz6 (ORCPT ); Mon, 14 Apr 2014 23:55:58 -0400 MIME-Version: 1.0 In-Reply-To: <534C3C65.1030808@codeaurora.org> References: <74d448a200afd0424fb185e2fb2ac5c31fd6b205.1397492345.git.viresh.kumar@linaro.org> <534C3C65.1030808@codeaurora.org> Date: Tue, 15 Apr 2014 09:25:57 +0530 Message-ID: Subject: Re: [PATCH 22/38] tick-sched: no need to recheck cpu_online() in can_stop_idle_tick() From: Viresh Kumar To: Stephen Boyd Cc: Thomas Gleixner , Lists linaro-kernel , Linux Kernel Mailing List , =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= , Arvind Chauhan , Linaro Networking Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15 April 2014 01:22, Stephen Boyd wrote: > On 04/14/14 09:23, Viresh Kumar wrote: >> We have already checked if 'cpu' is online or not and so don't need to recheck >> it. >> >> Signed-off-by: Viresh Kumar > > Hm... doing some git archeology shows fa116ea35ec7 (nohz: no softirq > pending warnings for offline cpus, 2008-12-11), where the cpu_online() > check was added. Before that commit we already checked cpu_online() > similar to how the code is today. Perhaps we need to add a comment here? Okay, I didn't understood what you want completely. You want me to update commit logs or drop this patch and update code? But yes there is one more thing worth mentioning: commit f7ea0fd6 (tick: Don't invoke tick_nohz_stop_sched_tick() if the cpu is offline, May 13 2013), which did this: diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 0eed1db..0121421 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -469,6 +469,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) if (unlikely(!cpu_online(cpu))) { if (cpu == tick_do_timer_cpu) tick_do_timer_cpu = TICK_DO_TIMER_NONE; + return false; } if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) So, when the patch you mentioned was added, we didn't had this and a recheck of cpu_online() was perhaps required. But it is surely not required anymore. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/