Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933379AbaGURv5 (ORCPT ); Mon, 21 Jul 2014 13:51:57 -0400 Received: from e39.co.us.ibm.com ([32.97.110.160]:39877 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932647AbaGURv4 (ORCPT ); Mon, 21 Jul 2014 13:51:56 -0400 Date: Mon, 21 Jul 2014 10:51:50 -0700 From: "Paul E. McKenney" To: Frederic Weisbecker Cc: LKML , Ingo Molnar , Peter Zijlstra , Steven Rostedt , Thomas Gleixner , Viresh Kumar Subject: Re: [PATCH 10/10] nohz: Warn on illegal timekeeper switch in nohz full Message-ID: <20140721175150.GE8690@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1405730661-9355-1-git-send-email-fweisbec@gmail.com> <1405730661-9355-11-git-send-email-fweisbec@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1405730661-9355-11-git-send-email-fweisbec@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14072117-9332-0000-0000-00000173EFD6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 19, 2014 at 02:44:21AM +0200, Frederic Weisbecker wrote: > 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 Acked-by: Paul E. McKenney > --- > 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/