diff options
| -rw-r--r-- | kernel/time/tick-common.c | 50 | ||||
| -rw-r--r-- | kernel/time/tick-sched.c | 34 |
2 files changed, 70 insertions, 14 deletions
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index df401463a191..e49e8091f9ac 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -46,6 +46,14 @@ ktime_t tick_period; * procedure also covers cpu hotplug. */ int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT; +#ifdef CONFIG_NO_HZ_FULL +/* + * tick_do_timer_boot_cpu indicates the boot CPU temporarily owns + * tick_do_timer_cpu and it should be taken over by an eligible secondary + * when one comes online. + */ +static int tick_do_timer_boot_cpu __read_mostly = -1; +#endif /* * Debugging: see timer_list.c @@ -167,6 +175,26 @@ void tick_setup_periodic(struct clock_event_device *dev, int broadcast) } } +#ifdef CONFIG_NO_HZ_FULL +static void giveup_do_timer(void *info) +{ + int cpu = *(unsigned int *)info; + + WARN_ON(tick_do_timer_cpu != smp_processor_id()); + + tick_do_timer_cpu = cpu; +} + +static void tick_take_do_timer_from_boot(void) +{ + int cpu = smp_processor_id(); + int from = tick_do_timer_boot_cpu; + + if (from >= 0 && from != cpu) + smp_call_function_single(from, giveup_do_timer, &cpu, 1); +} +#endif + /* * Setup the tick device */ @@ -186,12 +214,26 @@ static void tick_setup_device(struct tick_device *td, * this cpu: */ if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) { - if (!tick_nohz_full_cpu(cpu)) - tick_do_timer_cpu = cpu; - else - tick_do_timer_cpu = TICK_DO_TIMER_NONE; + tick_do_timer_cpu = cpu; + tick_next_period = ktime_get(); tick_period = NSEC_PER_SEC / HZ; +#ifdef CONFIG_NO_HZ_FULL + /* + * The boot CPU may be nohz_full, in which case set + * tick_do_timer_boot_cpu so the first housekeeping + * secondary that comes up will take do_timer from + * us. + */ + if (tick_nohz_full_cpu(cpu)) + tick_do_timer_boot_cpu = cpu; + + } else if (tick_do_timer_boot_cpu != -1 && + !tick_nohz_full_cpu(cpu)) { + tick_take_do_timer_from_boot(); + tick_do_timer_boot_cpu = -1; + WARN_ON(tick_do_timer_cpu != cpu); +#endif } /* diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 6fa52cd6df0b..4aa917acbe1c 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -121,10 +121,16 @@ static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now) * into a long sleep. If two CPUs happen to assign themselves to * this duty, then the jiffies update is still serialized by * jiffies_lock. + * + * If nohz_full is enabled, this should not happen because the + * tick_do_timer_cpu never relinquishes. */ - if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE) - && !tick_nohz_full_cpu(cpu)) + if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) { +#ifdef CONFIG_NO_HZ_FULL + WARN_ON(tick_nohz_full_running); +#endif tick_do_timer_cpu = cpu; + } #endif /* Check, if the jiffies need an update */ @@ -395,8 +401,8 @@ void __init tick_nohz_full_setup(cpumask_var_t cpumask) static int tick_nohz_cpu_down(unsigned int cpu) { /* - * The boot CPU handles housekeeping duty (unbound timers, - * workqueues, timekeeping, ...) on behalf of full dynticks + * The tick_do_timer_cpu 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) @@ -423,12 +429,15 @@ void __init tick_nohz_init(void) return; } - cpu = smp_processor_id(); + if (IS_ENABLED(CONFIG_PM_SLEEP_SMP) && + !IS_ENABLED(CONFIG_PM_SLEEP_SMP_NONZERO_CPU)) { + cpu = smp_processor_id(); - if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) { - pr_warn("NO_HZ: Clearing %d from nohz_full range for timekeeping\n", - cpu); - cpumask_clear_cpu(cpu, tick_nohz_full_mask); + if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) { + pr_warn("NO_HZ: Clearing %d from nohz_full range " + "for timekeeping\n", cpu); + cpumask_clear_cpu(cpu, tick_nohz_full_mask); + } } for_each_cpu(cpu, tick_nohz_full_mask) @@ -904,8 +913,13 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) /* * Boot safety: make sure the timekeeping duty has been * assigned before entering dyntick-idle mode, + * tick_do_timer_cpu is TICK_DO_TIMER_BOOT */ - if (tick_do_timer_cpu == TICK_DO_TIMER_NONE) + if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_BOOT)) + return false; + + /* Should not happen for nohz-full */ + if (WARN_ON_ONCE(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) return false; } |