From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1032468AbeBOAsd (ORCPT ); Wed, 14 Feb 2018 19:48:33 -0500 Received: from mail.kernel.org ([198.145.29.99]:58810 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1032447AbeBOAs3 (ORCPT ); Wed, 14 Feb 2018 19:48:29 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4A5FA217A0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=frederic@kernel.org From: Frederic Weisbecker To: Ingo Molnar Cc: LKML , Frederic Weisbecker , Peter Zijlstra , Chris Metcalf , Thomas Gleixner , Luiz Capitulino , Christoph Lameter , "Paul E . McKenney" , Wanpeng Li , Mike Galbraith , Rik van Riel Subject: [PATCH 2/6] nohz: Allow to check if remote CPU tick is stopped Date: Thu, 15 Feb 2018 01:48:10 +0100 Message-Id: <1518655694-8057-3-git-send-email-frederic@kernel.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1518655694-8057-1-git-send-email-frederic@kernel.org> References: <1518655694-8057-1-git-send-email-frederic@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This check is racy but provides a good heuristic to determine whether a CPU may need a remote tick or not. Signed-off-by: Frederic Weisbecker Cc: Chris Metcalf Cc: Christoph Lameter Cc: Luiz Capitulino Cc: Mike Galbraith Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Wanpeng Li Cc: Ingo Molnar --- include/linux/tick.h | 2 ++ kernel/time/tick-sched.c | 7 +++++++ 2 files changed, 9 insertions(+) diff --git a/include/linux/tick.h b/include/linux/tick.h index 7cc3592..944c829 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -114,6 +114,7 @@ enum tick_dep_bits { #ifdef CONFIG_NO_HZ_COMMON extern bool tick_nohz_enabled; extern int tick_nohz_tick_stopped(void); +extern int tick_nohz_tick_stopped_cpu(int cpu); extern void tick_nohz_idle_enter(void); extern void tick_nohz_idle_exit(void); extern void tick_nohz_irq_exit(void); @@ -125,6 +126,7 @@ extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time); #else /* !CONFIG_NO_HZ_COMMON */ #define tick_nohz_enabled (0) static inline int tick_nohz_tick_stopped(void) { return 0; } +static inline int tick_nohz_tick_stopped_cpu(int cpu) { return 0; } static inline void tick_nohz_idle_enter(void) { } static inline void tick_nohz_idle_exit(void) { } diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 29a5733..b517485 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -486,6 +486,13 @@ int tick_nohz_tick_stopped(void) return __this_cpu_read(tick_cpu_sched.tick_stopped); } +int tick_nohz_tick_stopped_cpu(int cpu) +{ + struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu); + + return ts->tick_stopped; +} + /** * tick_nohz_update_jiffies - update jiffies when idle was interrupted * -- 2.7.4