From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755065AbbIBP6y (ORCPT ); Wed, 2 Sep 2015 11:58:54 -0400 Received: from terminus.zytor.com ([198.137.202.10]:52324 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754881AbbIBP6v (ORCPT ); Wed, 2 Sep 2015 11:58:51 -0400 Date: Wed, 2 Sep 2015 08:57:59 -0700 From: tip-bot for Frederic Weisbecker Message-ID: Cc: tglx@linutronix.de, preeti@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, peterz@infradead.org, torvalds@linux-foundation.org, hpa@zytor.com, mingo@kernel.org, cmetcalf@ezchip.com, fweisbec@gmail.com, cl@linux.com, vatikaharlalka@gmail.com, paulmck@linux.vnet.ibm.com Reply-To: hpa@zytor.com, peterz@infradead.org, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, preeti@linux.vnet.ibm.com, tglx@linutronix.de, cmetcalf@ezchip.com, mingo@kernel.org, cl@linux.com, fweisbec@gmail.com, paulmck@linux.vnet.ibm.com, vatikaharlalka@gmail.com In-Reply-To: <1441119060-2230-3-git-send-email-fweisbec@gmail.com> References: <1441119060-2230-3-git-send-email-fweisbec@gmail.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] nohz: Assert existing housekeepers when nohz full enabled Git-Commit-ID: 7c8bb6cb95061b3143759459ed6c6b0c73bcfecb X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 7c8bb6cb95061b3143759459ed6c6b0c73bcfecb Gitweb: http://git.kernel.org/tip/7c8bb6cb95061b3143759459ed6c6b0c73bcfecb Author: Frederic Weisbecker AuthorDate: Tue, 1 Sep 2015 16:51:00 +0200 Committer: Ingo Molnar CommitDate: Wed, 2 Sep 2015 10:33:22 +0200 nohz: Assert existing housekeepers when nohz full enabled The code ensures that when nohz full is running, at least the boot CPU serves as a housekeeper and it can't be later offlined. Let's assert this assumption to make sure that we have CPUs to handle unbound jobs like workqueues and timers while nohz full CPUs run undisturbed. Also improve the comments on housekeeper offlining prevention. Signed-off-by: Frederic Weisbecker Acked-by: Thomas Gleixner Cc: Chris Metcalf Cc: Christoph Lameter Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Preeti U Murthy Cc: Vatika Harlalka Link: http://lkml.kernel.org/r/1441119060-2230-3-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar --- kernel/time/tick-sched.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 3319e16..7c7ec45 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -290,16 +290,17 @@ static int __init tick_nohz_full_setup(char *str) __setup("nohz_full=", tick_nohz_full_setup); static int tick_nohz_cpu_down_callback(struct notifier_block *nfb, - unsigned long action, - void *hcpu) + unsigned long action, + void *hcpu) { unsigned int cpu = (unsigned long)hcpu; switch (action & ~CPU_TASKS_FROZEN) { case CPU_DOWN_PREPARE: /* - * If we handle the timekeeping duty for full dynticks CPUs, - * we can't safely shutdown that CPU. + * The boot CPU handles housekeeping duty (unbound timers, + * workqueues, timekeeping, ...) on behalf of full dynticks + * CPUs. It must remain online when nohz full is enabled. */ if (tick_nohz_full_running && tick_do_timer_cpu == cpu) return NOTIFY_BAD; @@ -370,6 +371,12 @@ void __init tick_nohz_init(void) cpu_notifier(tick_nohz_cpu_down_callback, 0); pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n", cpumask_pr_args(tick_nohz_full_mask)); + + /* + * We need at least one CPU to handle housekeeping work such + * as timekeeping, unbound timers, workqueues, ... + */ + WARN_ON_ONCE(cpumask_empty(housekeeping_mask)); } #endif