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 <mi...@kernel.org>
> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Steven Rostedt <rost...@goodmis.org>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Viresh Kumar <viresh.ku...@linaro.org>
> Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
Acked-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
> ---
> 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 majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
