Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934062AbaGSAqo (ORCPT ); Fri, 18 Jul 2014 20:46:44 -0400 Received: from mail-wi0-f174.google.com ([209.85.212.174]:57466 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758164AbaGSAom (ORCPT ); Fri, 18 Jul 2014 20:44:42 -0400 From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Ingo Molnar , "Paul E. McKenney" , Peter Zijlstra , Steven Rostedt , Thomas Gleixner , Viresh Kumar Subject: [PATCH 10/10] nohz: Warn on illegal timekeeper switch in nohz full Date: Sat, 19 Jul 2014 02:44:21 +0200 Message-Id: <1405730661-9355-11-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1405730661-9355-1-git-send-email-fweisbec@gmail.com> References: <1405730661-9355-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In full dynticks idle mode, the timekeeper should never be set to another CPU than 0. Lets enforce that through a dedicated mutator. Cc: Ingo Molnar Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Viresh Kumar Signed-off-by: Frederic Weisbecker --- kernel/time/tick-common.c | 9 ++++----- kernel/time/tick-internal.h | 7 +++++++ kernel/time/tick-sched.c | 7 +++---- 3 files changed, 14 insertions(+), 9 deletions(-) diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index cb57bce..72ccaf2 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -180,9 +180,9 @@ static void tick_setup_device(struct tick_device *td, */ if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) { if (tick_nohz_full_enabled()) - tick_do_timer_cpu = TICK_DO_TIMER_DEFAULT; + tick_do_timer_cpu_set(TICK_DO_TIMER_DEFAULT); else - tick_do_timer_cpu = cpu; + tick_do_timer_cpu_set(cpu); tick_next_period = ktime_get(); tick_period = ktime_set(0, NSEC_PER_SEC / HZ); } @@ -341,9 +341,8 @@ void tick_handover_do_timer(int *cpup) { if (*cpup == tick_do_timer_cpu) { int cpu = cpumask_first(cpu_online_mask); - - tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu : - TICK_DO_TIMER_NONE; + tick_do_timer_cpu_set((cpu < nr_cpu_ids) ? cpu : + TICK_DO_TIMER_NONE); } } diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h index 6b592a8..eadfd89 100644 --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -23,6 +23,13 @@ extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast); extern void tick_handle_periodic(struct clock_event_device *dev); extern void tick_check_new_device(struct clock_event_device *dev); extern void tick_handover_do_timer(int *cpup); + +static inline void tick_do_timer_cpu_set(int cpu) +{ + WARN_ON_ONCE(tick_nohz_full_enabled() && cpu != TICK_DO_TIMER_DEFAULT); + tick_do_timer_cpu = cpu; +} + extern void tick_shutdown(unsigned int *cpup); extern void tick_suspend(void); extern void tick_resume(void); diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 845aaff..3b5102a 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -123,7 +123,7 @@ static void tick_sched_do_timer(ktime_t now) */ if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE) && !tick_nohz_full_cpu(cpu)) - tick_do_timer_cpu = cpu; + tick_do_timer_cpu_set(cpu); #endif /* Check, if the jiffies need an update */ @@ -550,7 +550,7 @@ static u64 timekeeping_deferment(struct tick_sched *ts, int cpu) ts->do_timer_last = 1; /* In full dynticks mode, CPU 0 always keeps the duty */ if (!tick_nohz_full_enabled()) - tick_do_timer_cpu = TICK_DO_TIMER_NONE; + tick_do_timer_cpu_set(TICK_DO_TIMER_NONE); } else if (ts->do_timer_last) { if (tick_do_timer_cpu == TICK_DO_TIMER_NONE) time_delta = timekeeping_max_deferment(); @@ -600,7 +600,6 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts, /* Schedule the tick, if we are at least one jiffie off */ if ((long)delta_jiffies >= 1) { u64 time_delta = timekeeping_deferment(ts, cpu); - #ifdef CONFIG_NO_HZ_FULL if (!ts->inidle) { time_delta = min(time_delta, @@ -717,7 +716,7 @@ 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; + tick_do_timer_cpu_set(TICK_DO_TIMER_NONE); return false; } -- 1.8.3.1 -- 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/