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Diffstat (limited to 'kernel/time/tick-sched.c')
| -rw-r--r-- | kernel/time/tick-sched.c | 1617 |
1 files changed, 1617 insertions, 0 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c new file mode 100644 index 0000000000..55cbc49f70 --- /dev/null +++ b/kernel/time/tick-sched.c @@ -0,0 +1,1617 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> + * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar + * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner + * + * No idle tick implementation for low and high resolution timers + * + * Started by: Thomas Gleixner and Ingo Molnar + */ +#include <linux/cpu.h> +#include <linux/err.h> +#include <linux/hrtimer.h> +#include <linux/interrupt.h> +#include <linux/kernel_stat.h> +#include <linux/percpu.h> +#include <linux/nmi.h> +#include <linux/profile.h> +#include <linux/sched/signal.h> +#include <linux/sched/clock.h> +#include <linux/sched/stat.h> +#include <linux/sched/nohz.h> +#include <linux/sched/loadavg.h> +#include <linux/module.h> +#include <linux/irq_work.h> +#include <linux/posix-timers.h> +#include <linux/context_tracking.h> +#include <linux/mm.h> + +#include <asm/irq_regs.h> + +#include "tick-internal.h" + +#include <trace/events/timer.h> + +/* + * Per-CPU nohz control structure + */ +static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched); + +struct tick_sched *tick_get_tick_sched(int cpu) +{ + return &per_cpu(tick_cpu_sched, cpu); +} + +#if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS) +/* + * The time, when the last jiffy update happened. Write access must hold + * jiffies_lock and jiffies_seq. tick_nohz_next_event() needs to get a + * consistent view of jiffies and last_jiffies_update. + */ +static ktime_t last_jiffies_update; + +/* + * Must be called with interrupts disabled ! + */ +static void tick_do_update_jiffies64(ktime_t now) +{ + unsigned long ticks = 1; + ktime_t delta, nextp; + + /* + * 64bit can do a quick check without holding jiffies lock and + * without looking at the sequence count. The smp_load_acquire() + * pairs with the update done later in this function. + * + * 32bit cannot do that because the store of tick_next_period + * consists of two 32bit stores and the first store could move it + * to a random point in the future. + */ + if (IS_ENABLED(CONFIG_64BIT)) { + if (ktime_before(now, smp_load_acquire(&tick_next_period))) + return; + } else { + unsigned int seq; + + /* + * Avoid contention on jiffies_lock and protect the quick + * check with the sequence count. + */ + do { + seq = read_seqcount_begin(&jiffies_seq); + nextp = tick_next_period; + } while (read_seqcount_retry(&jiffies_seq, seq)); + + if (ktime_before(now, nextp)) + return; + } + + /* Quick check failed, i.e. update is required. */ + raw_spin_lock(&jiffies_lock); + /* + * Reevaluate with the lock held. Another CPU might have done the + * update already. + */ + if (ktime_before(now, tick_next_period)) { + raw_spin_unlock(&jiffies_lock); + return; + } + + write_seqcount_begin(&jiffies_seq); + + delta = ktime_sub(now, tick_next_period); + if (unlikely(delta >= TICK_NSEC)) { + /* Slow path for long idle sleep times */ + s64 incr = TICK_NSEC; + + ticks += ktime_divns(delta, incr); + + last_jiffies_update = ktime_add_ns(last_jiffies_update, + incr * ticks); + } else { + last_jiffies_update = ktime_add_ns(last_jiffies_update, + TICK_NSEC); + } + + /* Advance jiffies to complete the jiffies_seq protected job */ + jiffies_64 += ticks; + + /* + * Keep the tick_next_period variable up to date. + */ + nextp = ktime_add_ns(last_jiffies_update, TICK_NSEC); + + if (IS_ENABLED(CONFIG_64BIT)) { + /* + * Pairs with smp_load_acquire() in the lockless quick + * check above and ensures that the update to jiffies_64 is + * not reordered vs. the store to tick_next_period, neither + * by the compiler nor by the CPU. + */ + smp_store_release(&tick_next_period, nextp); + } else { + /* + * A plain store is good enough on 32bit as the quick check + * above is protected by the sequence count. + */ + tick_next_period = nextp; + } + + /* + * Release the sequence count. calc_global_load() below is not + * protected by it, but jiffies_lock needs to be held to prevent + * concurrent invocations. + */ + write_seqcount_end(&jiffies_seq); + + calc_global_load(); + + raw_spin_unlock(&jiffies_lock); + update_wall_time(); +} + +/* + * Initialize and return retrieve the jiffies update. + */ +static ktime_t tick_init_jiffy_update(void) +{ + ktime_t period; + + raw_spin_lock(&jiffies_lock); + write_seqcount_begin(&jiffies_seq); + /* Did we start the jiffies update yet ? */ + if (last_jiffies_update == 0) { + u32 rem; + + /* + * Ensure that the tick is aligned to a multiple of + * TICK_NSEC. + */ + div_u64_rem(tick_next_period, TICK_NSEC, &rem); + if (rem) + tick_next_period += TICK_NSEC - rem; + + last_jiffies_update = tick_next_period; + } + period = last_jiffies_update; + write_seqcount_end(&jiffies_seq); + raw_spin_unlock(&jiffies_lock); + return period; +} + +#define MAX_STALLED_JIFFIES 5 + +static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now) +{ + int cpu = smp_processor_id(); + +#ifdef CONFIG_NO_HZ_COMMON + /* + * Check if the do_timer duty was dropped. We don't care about + * concurrency: This happens only when the CPU in charge went + * 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)) { +#ifdef CONFIG_NO_HZ_FULL + WARN_ON_ONCE(tick_nohz_full_running); +#endif + tick_do_timer_cpu = cpu; + } +#endif + + /* Check, if the jiffies need an update */ + if (tick_do_timer_cpu == cpu) + tick_do_update_jiffies64(now); + + /* + * If jiffies update stalled for too long (timekeeper in stop_machine() + * or VMEXIT'ed for several msecs), force an update. + */ + if (ts->last_tick_jiffies != jiffies) { + ts->stalled_jiffies = 0; + ts->last_tick_jiffies = READ_ONCE(jiffies); + } else { + if (++ts->stalled_jiffies == MAX_STALLED_JIFFIES) { + tick_do_update_jiffies64(now); + ts->stalled_jiffies = 0; + ts->last_tick_jiffies = READ_ONCE(jiffies); + } + } + + if (ts->inidle) + ts->got_idle_tick = 1; +} + +static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs) +{ +#ifdef CONFIG_NO_HZ_COMMON + /* + * When we are idle and the tick is stopped, we have to touch + * the watchdog as we might not schedule for a really long + * time. This happens on complete idle SMP systems while + * waiting on the login prompt. We also increment the "start of + * idle" jiffy stamp so the idle accounting adjustment we do + * when we go busy again does not account too much ticks. + */ + if (ts->tick_stopped) { + touch_softlockup_watchdog_sched(); + if (is_idle_task(current)) + ts->idle_jiffies++; + /* + * In case the current tick fired too early past its expected + * expiration, make sure we don't bypass the next clock reprogramming + * to the same deadline. + */ + ts->next_tick = 0; + } +#endif + update_process_times(user_mode(regs)); + profile_tick(CPU_PROFILING); +} +#endif + +#ifdef CONFIG_NO_HZ_FULL +cpumask_var_t tick_nohz_full_mask; +EXPORT_SYMBOL_GPL(tick_nohz_full_mask); +bool tick_nohz_full_running; +EXPORT_SYMBOL_GPL(tick_nohz_full_running); +static atomic_t tick_dep_mask; + +static bool check_tick_dependency(atomic_t *dep) +{ + int val = atomic_read(dep); + + if (val & TICK_DEP_MASK_POSIX_TIMER) { + trace_tick_stop(0, TICK_DEP_MASK_POSIX_TIMER); + return true; + } + + if (val & TICK_DEP_MASK_PERF_EVENTS) { + trace_tick_stop(0, TICK_DEP_MASK_PERF_EVENTS); + return true; + } + + if (val & TICK_DEP_MASK_SCHED) { + trace_tick_stop(0, TICK_DEP_MASK_SCHED); + return true; + } + + if (val & TICK_DEP_MASK_CLOCK_UNSTABLE) { + trace_tick_stop(0, TICK_DEP_MASK_CLOCK_UNSTABLE); + return true; + } + + if (val & TICK_DEP_MASK_RCU) { + trace_tick_stop(0, TICK_DEP_MASK_RCU); + return true; + } + + if (val & TICK_DEP_MASK_RCU_EXP) { + trace_tick_stop(0, TICK_DEP_MASK_RCU_EXP); + return true; + } + + return false; +} + +static bool can_stop_full_tick(int cpu, struct tick_sched *ts) +{ + lockdep_assert_irqs_disabled(); + + if (unlikely(!cpu_online(cpu))) + return false; + + if (check_tick_dependency(&tick_dep_mask)) + return false; + + if (check_tick_dependency(&ts->tick_dep_mask)) + return false; + + if (check_tick_dependency(¤t->tick_dep_mask)) + return false; + + if (check_tick_dependency(¤t->signal->tick_dep_mask)) + return false; + + return true; +} + +static void nohz_full_kick_func(struct irq_work *work) +{ + /* Empty, the tick restart happens on tick_nohz_irq_exit() */ +} + +static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = + IRQ_WORK_INIT_HARD(nohz_full_kick_func); + +/* + * Kick this CPU if it's full dynticks in order to force it to + * re-evaluate its dependency on the tick and restart it if necessary. + * This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(), + * is NMI safe. + */ +static void tick_nohz_full_kick(void) +{ + if (!tick_nohz_full_cpu(smp_processor_id())) + return; + + irq_work_queue(this_cpu_ptr(&nohz_full_kick_work)); +} + +/* + * Kick the CPU if it's full dynticks in order to force it to + * re-evaluate its dependency on the tick and restart it if necessary. + */ +void tick_nohz_full_kick_cpu(int cpu) +{ + if (!tick_nohz_full_cpu(cpu)) + return; + + irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu); +} + +static void tick_nohz_kick_task(struct task_struct *tsk) +{ + int cpu; + + /* + * If the task is not running, run_posix_cpu_timers() + * has nothing to elapse, IPI can then be spared. + * + * activate_task() STORE p->tick_dep_mask + * STORE p->on_rq + * __schedule() (switch to task 'p') smp_mb() (atomic_fetch_or()) + * LOCK rq->lock LOAD p->on_rq + * smp_mb__after_spin_lock() + * tick_nohz_task_switch() + * LOAD p->tick_dep_mask + */ + if (!sched_task_on_rq(tsk)) + return; + + /* + * If the task concurrently migrates to another CPU, + * we guarantee it sees the new tick dependency upon + * schedule. + * + * set_task_cpu(p, cpu); + * STORE p->cpu = @cpu + * __schedule() (switch to task 'p') + * LOCK rq->lock + * smp_mb__after_spin_lock() STORE p->tick_dep_mask + * tick_nohz_task_switch() smp_mb() (atomic_fetch_or()) + * LOAD p->tick_dep_mask LOAD p->cpu + */ + cpu = task_cpu(tsk); + + preempt_disable(); + if (cpu_online(cpu)) + tick_nohz_full_kick_cpu(cpu); + preempt_enable(); +} + +/* + * Kick all full dynticks CPUs in order to force these to re-evaluate + * their dependency on the tick and restart it if necessary. + */ +static void tick_nohz_full_kick_all(void) +{ + int cpu; + + if (!tick_nohz_full_running) + return; + + preempt_disable(); + for_each_cpu_and(cpu, tick_nohz_full_mask, cpu_online_mask) + tick_nohz_full_kick_cpu(cpu); + preempt_enable(); +} + +static void tick_nohz_dep_set_all(atomic_t *dep, + enum tick_dep_bits bit) +{ + int prev; + + prev = atomic_fetch_or(BIT(bit), dep); + if (!prev) + tick_nohz_full_kick_all(); +} + +/* + * Set a global tick dependency. Used by perf events that rely on freq and + * by unstable clock. + */ +void tick_nohz_dep_set(enum tick_dep_bits bit) +{ + tick_nohz_dep_set_all(&tick_dep_mask, bit); +} + +void tick_nohz_dep_clear(enum tick_dep_bits bit) +{ + atomic_andnot(BIT(bit), &tick_dep_mask); +} + +/* + * Set per-CPU tick dependency. Used by scheduler and perf events in order to + * manage events throttling. + */ +void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit) +{ + int prev; + struct tick_sched *ts; + + ts = per_cpu_ptr(&tick_cpu_sched, cpu); + + prev = atomic_fetch_or(BIT(bit), &ts->tick_dep_mask); + if (!prev) { + preempt_disable(); + /* Perf needs local kick that is NMI safe */ + if (cpu == smp_processor_id()) { + tick_nohz_full_kick(); + } else { + /* Remote irq work not NMI-safe */ + if (!WARN_ON_ONCE(in_nmi())) + tick_nohz_full_kick_cpu(cpu); + } + preempt_enable(); + } +} +EXPORT_SYMBOL_GPL(tick_nohz_dep_set_cpu); + +void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit) +{ + struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu); + + atomic_andnot(BIT(bit), &ts->tick_dep_mask); +} +EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_cpu); + +/* + * Set a per-task tick dependency. RCU need this. Also posix CPU timers + * in order to elapse per task timers. + */ +void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit) +{ + if (!atomic_fetch_or(BIT(bit), &tsk->tick_dep_mask)) + tick_nohz_kick_task(tsk); +} +EXPORT_SYMBOL_GPL(tick_nohz_dep_set_task); + +void tick_nohz_dep_clear_task(struct task_struct *tsk, enum tick_dep_bits bit) +{ + atomic_andnot(BIT(bit), &tsk->tick_dep_mask); +} +EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_task); + +/* + * Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse + * per process timers. + */ +void tick_nohz_dep_set_signal(struct task_struct *tsk, + enum tick_dep_bits bit) +{ + int prev; + struct signal_struct *sig = tsk->signal; + + prev = atomic_fetch_or(BIT(bit), &sig->tick_dep_mask); + if (!prev) { + struct task_struct *t; + + lockdep_assert_held(&tsk->sighand->siglock); + __for_each_thread(sig, t) + tick_nohz_kick_task(t); + } +} + +void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bit) +{ + atomic_andnot(BIT(bit), &sig->tick_dep_mask); +} + +/* + * Re-evaluate the need for the tick as we switch the current task. + * It might need the tick due to per task/process properties: + * perf events, posix CPU timers, ... + */ +void __tick_nohz_task_switch(void) +{ + struct tick_sched *ts; + + if (!tick_nohz_full_cpu(smp_processor_id())) + return; + + ts = this_cpu_ptr(&tick_cpu_sched); + + if (ts->tick_stopped) { + if (atomic_read(¤t->tick_dep_mask) || + atomic_read(¤t->signal->tick_dep_mask)) + tick_nohz_full_kick(); + } +} + +/* Get the boot-time nohz CPU list from the kernel parameters. */ +void __init tick_nohz_full_setup(cpumask_var_t cpumask) +{ + alloc_bootmem_cpumask_var(&tick_nohz_full_mask); + cpumask_copy(tick_nohz_full_mask, cpumask); + tick_nohz_full_running = true; +} + +bool tick_nohz_cpu_hotpluggable(unsigned int cpu) +{ + /* + * 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) + return false; + return true; +} + +static int tick_nohz_cpu_down(unsigned int cpu) +{ + return tick_nohz_cpu_hotpluggable(cpu) ? 0 : -EBUSY; +} + +void __init tick_nohz_init(void) +{ + int cpu, ret; + + if (!tick_nohz_full_running) + return; + + /* + * Full dynticks uses irq work to drive the tick rescheduling on safe + * locking contexts. But then we need irq work to raise its own + * interrupts to avoid circular dependency on the tick + */ + if (!arch_irq_work_has_interrupt()) { + pr_warn("NO_HZ: Can't run full dynticks because arch doesn't support irq work self-IPIs\n"); + cpumask_clear(tick_nohz_full_mask); + tick_nohz_full_running = false; + return; + } + + 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); + } + } + + for_each_cpu(cpu, tick_nohz_full_mask) + ct_cpu_track_user(cpu); + + ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, + "kernel/nohz:predown", NULL, + tick_nohz_cpu_down); + WARN_ON(ret < 0); + pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n", + cpumask_pr_args(tick_nohz_full_mask)); +} +#endif + +/* + * NOHZ - aka dynamic tick functionality + */ +#ifdef CONFIG_NO_HZ_COMMON +/* + * NO HZ enabled ? + */ +bool tick_nohz_enabled __read_mostly = true; +unsigned long tick_nohz_active __read_mostly; +/* + * Enable / Disable tickless mode + */ +static int __init setup_tick_nohz(char *str) +{ + return (kstrtobool(str, &tick_nohz_enabled) == 0); +} + +__setup("nohz=", setup_tick_nohz); + +bool tick_nohz_tick_stopped(void) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + + return ts->tick_stopped; +} + +bool 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 + * + * Called from interrupt entry when the CPU was idle + * + * In case the sched_tick was stopped on this CPU, we have to check if jiffies + * must be updated. Otherwise an interrupt handler could use a stale jiffy + * value. We do this unconditionally on any CPU, as we don't know whether the + * CPU, which has the update task assigned is in a long sleep. + */ +static void tick_nohz_update_jiffies(ktime_t now) +{ + unsigned long flags; + + __this_cpu_write(tick_cpu_sched.idle_waketime, now); + + local_irq_save(flags); + tick_do_update_jiffies64(now); + local_irq_restore(flags); + + touch_softlockup_watchdog_sched(); +} + +static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now) +{ + ktime_t delta; + + if (WARN_ON_ONCE(!ts->idle_active)) + return; + + delta = ktime_sub(now, ts->idle_entrytime); + + write_seqcount_begin(&ts->idle_sleeptime_seq); + if (nr_iowait_cpu(smp_processor_id()) > 0) + ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta); + else + ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); + + ts->idle_entrytime = now; + ts->idle_active = 0; + write_seqcount_end(&ts->idle_sleeptime_seq); + + sched_clock_idle_wakeup_event(); +} + +static void tick_nohz_start_idle(struct tick_sched *ts) +{ + write_seqcount_begin(&ts->idle_sleeptime_seq); + ts->idle_entrytime = ktime_get(); + ts->idle_active = 1; + write_seqcount_end(&ts->idle_sleeptime_seq); + + sched_clock_idle_sleep_event(); +} + +static u64 get_cpu_sleep_time_us(struct tick_sched *ts, ktime_t *sleeptime, + bool compute_delta, u64 *last_update_time) +{ + ktime_t now, idle; + unsigned int seq; + + if (!tick_nohz_active) + return -1; + + now = ktime_get(); + if (last_update_time) + *last_update_time = ktime_to_us(now); + + do { + seq = read_seqcount_begin(&ts->idle_sleeptime_seq); + + if (ts->idle_active && compute_delta) { + ktime_t delta = ktime_sub(now, ts->idle_entrytime); + + idle = ktime_add(*sleeptime, delta); + } else { + idle = *sleeptime; + } + } while (read_seqcount_retry(&ts->idle_sleeptime_seq, seq)); + + return ktime_to_us(idle); + +} + +/** + * get_cpu_idle_time_us - get the total idle time of a CPU + * @cpu: CPU number to query + * @last_update_time: variable to store update time in. Do not update + * counters if NULL. + * + * Return the cumulative idle time (since boot) for a given + * CPU, in microseconds. Note this is partially broken due to + * the counter of iowait tasks that can be remotely updated without + * any synchronization. Therefore it is possible to observe backward + * values within two consecutive reads. + * + * This time is measured via accounting rather than sampling, + * and is as accurate as ktime_get() is. + * + * This function returns -1 if NOHZ is not enabled. + */ +u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) +{ + struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); + + return get_cpu_sleep_time_us(ts, &ts->idle_sleeptime, + !nr_iowait_cpu(cpu), last_update_time); +} +EXPORT_SYMBOL_GPL(get_cpu_idle_time_us); + +/** + * get_cpu_iowait_time_us - get the total iowait time of a CPU + * @cpu: CPU number to query + * @last_update_time: variable to store update time in. Do not update + * counters if NULL. + * + * Return the cumulative iowait time (since boot) for a given + * CPU, in microseconds. Note this is partially broken due to + * the counter of iowait tasks that can be remotely updated without + * any synchronization. Therefore it is possible to observe backward + * values within two consecutive reads. + * + * This time is measured via accounting rather than sampling, + * and is as accurate as ktime_get() is. + * + * This function returns -1 if NOHZ is not enabled. + */ +u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time) +{ + struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); + + return get_cpu_sleep_time_us(ts, &ts->iowait_sleeptime, + nr_iowait_cpu(cpu), last_update_time); +} +EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us); + +static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) +{ + hrtimer_cancel(&ts->sched_timer); + hrtimer_set_expires(&ts->sched_timer, ts->last_tick); + + /* Forward the time to expire in the future */ + hrtimer_forward(&ts->sched_timer, now, TICK_NSEC); + + if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { + hrtimer_start_expires(&ts->sched_timer, + HRTIMER_MODE_ABS_PINNED_HARD); + } else { + tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1); + } + + /* + * Reset to make sure next tick stop doesn't get fooled by past + * cached clock deadline. + */ + ts->next_tick = 0; +} + +static inline bool local_timer_softirq_pending(void) +{ + return local_softirq_pending() & BIT(TIMER_SOFTIRQ); +} + +static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu) +{ + u64 basemono, next_tick, delta, expires; + unsigned long basejiff; + unsigned int seq; + + /* Read jiffies and the time when jiffies were updated last */ + do { + seq = read_seqcount_begin(&jiffies_seq); + basemono = last_jiffies_update; + basejiff = jiffies; + } while (read_seqcount_retry(&jiffies_seq, seq)); + ts->last_jiffies = basejiff; + ts->timer_expires_base = basemono; + + /* + * Keep the periodic tick, when RCU, architecture or irq_work + * requests it. + * Aside of that check whether the local timer softirq is + * pending. If so its a bad idea to call get_next_timer_interrupt() + * because there is an already expired timer, so it will request + * immediate expiry, which rearms the hardware timer with a + * minimal delta which brings us back to this place + * immediately. Lather, rinse and repeat... + */ + if (rcu_needs_cpu() || arch_needs_cpu() || + irq_work_needs_cpu() || local_timer_softirq_pending()) { + next_tick = basemono + TICK_NSEC; + } else { + /* + * Get the next pending timer. If high resolution + * timers are enabled this only takes the timer wheel + * timers into account. If high resolution timers are + * disabled this also looks at the next expiring + * hrtimer. + */ + next_tick = get_next_timer_interrupt(basejiff, basemono); + ts->next_timer = next_tick; + } + + /* + * If the tick is due in the next period, keep it ticking or + * force prod the timer. + */ + delta = next_tick - basemono; + if (delta <= (u64)TICK_NSEC) { + /* + * Tell the timer code that the base is not idle, i.e. undo + * the effect of get_next_timer_interrupt(): + */ + timer_clear_idle(); + /* + * We've not stopped the tick yet, and there's a timer in the + * next period, so no point in stopping it either, bail. + */ + if (!ts->tick_stopped) { + ts->timer_expires = 0; + goto out; + } + } + + /* + * If this CPU is the one which had the do_timer() duty last, we limit + * the sleep time to the timekeeping max_deferment value. + * Otherwise we can sleep as long as we want. + */ + delta = timekeeping_max_deferment(); + if (cpu != tick_do_timer_cpu && + (tick_do_timer_cpu != TICK_DO_TIMER_NONE || !ts->do_timer_last)) + delta = KTIME_MAX; + + /* Calculate the next expiry time */ + if (delta < (KTIME_MAX - basemono)) + expires = basemono + delta; + else + expires = KTIME_MAX; + + ts->timer_expires = min_t(u64, expires, next_tick); + +out: + return ts->timer_expires; +} + +static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu) +{ + struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); + u64 basemono = ts->timer_expires_base; + u64 expires = ts->timer_expires; + ktime_t tick = expires; + + /* Make sure we won't be trying to stop it twice in a row. */ + ts->timer_expires_base = 0; + + /* + * If this CPU is the one which updates jiffies, then give up + * the assignment and let it be taken by the CPU which runs + * the tick timer next, which might be this CPU as well. If we + * don't drop this here the jiffies might be stale and + * do_timer() never invoked. Keep track of the fact that it + * was the one which had the do_timer() duty last. + */ + if (cpu == tick_do_timer_cpu) { + tick_do_timer_cpu = TICK_DO_TIMER_NONE; + ts->do_timer_last = 1; + } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) { + ts->do_timer_last = 0; + } + + /* Skip reprogram of event if its not changed */ + if (ts->tick_stopped && (expires == ts->next_tick)) { + /* Sanity check: make sure clockevent is actually programmed */ + if (tick == KTIME_MAX || ts->next_tick == hrtimer_get_expires(&ts->sched_timer)) + return; + + WARN_ON_ONCE(1); + printk_once("basemono: %llu ts->next_tick: %llu dev->next_event: %llu timer->active: %d timer->expires: %llu\n", + basemono, ts->next_tick, dev->next_event, + hrtimer_active(&ts->sched_timer), hrtimer_get_expires(&ts->sched_timer)); + } + + /* + * nohz_stop_sched_tick can be called several times before + * the nohz_restart_sched_tick is called. This happens when + * interrupts arrive which do not cause a reschedule. In the + * first call we save the current tick time, so we can restart + * the scheduler tick in nohz_restart_sched_tick. + */ + if (!ts->tick_stopped) { + calc_load_nohz_start(); + quiet_vmstat(); + + ts->last_tick = hrtimer_get_expires(&ts->sched_timer); + ts->tick_stopped = 1; + trace_tick_stop(1, TICK_DEP_MASK_NONE); + } + + ts->next_tick = tick; + + /* + * If the expiration time == KTIME_MAX, then we simply stop + * the tick timer. + */ + if (unlikely(expires == KTIME_MAX)) { + if (ts->nohz_mode == NOHZ_MODE_HIGHRES) + hrtimer_cancel(&ts->sched_timer); + else + tick_program_event(KTIME_MAX, 1); + return; + } + + if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { + hrtimer_start(&ts->sched_timer, tick, + HRTIMER_MODE_ABS_PINNED_HARD); + } else { + hrtimer_set_expires(&ts->sched_timer, tick); + tick_program_event(tick, 1); + } +} + +static void tick_nohz_retain_tick(struct tick_sched *ts) +{ + ts->timer_expires_base = 0; +} + +#ifdef CONFIG_NO_HZ_FULL +static void tick_nohz_stop_sched_tick(struct tick_sched *ts, int cpu) +{ + if (tick_nohz_next_event(ts, cpu)) + tick_nohz_stop_tick(ts, cpu); + else + tick_nohz_retain_tick(ts); +} +#endif /* CONFIG_NO_HZ_FULL */ + +static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now) +{ + /* Update jiffies first */ + tick_do_update_jiffies64(now); + + /* + * Clear the timer idle flag, so we avoid IPIs on remote queueing and + * the clock forward checks in the enqueue path: + */ + timer_clear_idle(); + + calc_load_nohz_stop(); + touch_softlockup_watchdog_sched(); + /* + * Cancel the scheduled timer and restore the tick + */ + ts->tick_stopped = 0; + tick_nohz_restart(ts, now); +} + +static void __tick_nohz_full_update_tick(struct tick_sched *ts, + ktime_t now) +{ +#ifdef CONFIG_NO_HZ_FULL + int cpu = smp_processor_id(); + + if (can_stop_full_tick(cpu, ts)) + tick_nohz_stop_sched_tick(ts, cpu); + else if (ts->tick_stopped) + tick_nohz_restart_sched_tick(ts, now); +#endif +} + +static void tick_nohz_full_update_tick(struct tick_sched *ts) +{ + if (!tick_nohz_full_cpu(smp_processor_id())) + return; + + if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) + return; + + __tick_nohz_full_update_tick(ts, ktime_get()); +} + +/* + * A pending softirq outside an IRQ (or softirq disabled section) context + * should be waiting for ksoftirqd to handle it. Therefore we shouldn't + * reach here due to the need_resched() early check in can_stop_idle_tick(). + * + * However if we are between CPUHP_AP_SMPBOOT_THREADS and CPU_TEARDOWN_CPU on the + * cpu_down() process, softirqs can still be raised while ksoftirqd is parked, + * triggering the below since wakep_softirqd() is ignored. + * + */ +static bool report_idle_softirq(void) +{ + static int ratelimit; + unsigned int pending = local_softirq_pending(); + + if (likely(!pending)) + return false; + + /* Some softirqs claim to be safe against hotplug and ksoftirqd parking */ + if (!cpu_active(smp_processor_id())) { + pending &= ~SOFTIRQ_HOTPLUG_SAFE_MASK; + if (!pending) + return false; + } + + if (ratelimit >= 10) + return false; + + /* On RT, softirqs handling may be waiting on some lock */ + if (local_bh_blocked()) + return false; + + pr_warn("NOHZ tick-stop error: local softirq work is pending, handler #%02x!!!\n", + pending); + ratelimit++; + + return true; +} + +static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) +{ + /* + * If this CPU is offline and it is the one which updates + * jiffies, then give up the assignment and let it be taken by + * the CPU which runs the tick timer next. If we don't drop + * this here the jiffies might be stale and do_timer() never + * invoked. + */ + if (unlikely(!cpu_online(cpu))) { + if (cpu == tick_do_timer_cpu) + tick_do_timer_cpu = TICK_DO_TIMER_NONE; + /* + * Make sure the CPU doesn't get fooled by obsolete tick + * deadline if it comes back online later. + */ + ts->next_tick = 0; + return false; + } + + if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) + return false; + + if (need_resched()) + return false; + + if (unlikely(report_idle_softirq())) + return false; + + if (tick_nohz_full_enabled()) { + /* + * Keep the tick alive to guarantee timekeeping progression + * if there are full dynticks CPUs around + */ + if (tick_do_timer_cpu == cpu) + return false; + + /* Should not happen for nohz-full */ + if (WARN_ON_ONCE(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) + return false; + } + + return true; +} + +/** + * tick_nohz_idle_stop_tick - stop the idle tick from the idle task + * + * When the next event is more than a tick into the future, stop the idle tick + */ +void tick_nohz_idle_stop_tick(void) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + int cpu = smp_processor_id(); + ktime_t expires; + + /* + * If tick_nohz_get_sleep_length() ran tick_nohz_next_event(), the + * tick timer expiration time is known already. + */ + if (ts->timer_expires_base) + expires = ts->timer_expires; + else if (can_stop_idle_tick(cpu, ts)) + expires = tick_nohz_next_event(ts, cpu); + else + return; + + ts->idle_calls++; + + if (expires > 0LL) { + int was_stopped = ts->tick_stopped; + + tick_nohz_stop_tick(ts, cpu); + + ts->idle_sleeps++; + ts->idle_expires = expires; + + if (!was_stopped && ts->tick_stopped) { + ts->idle_jiffies = ts->last_jiffies; + nohz_balance_enter_idle(cpu); + } + } else { + tick_nohz_retain_tick(ts); + } +} + +void tick_nohz_idle_retain_tick(void) +{ + tick_nohz_retain_tick(this_cpu_ptr(&tick_cpu_sched)); + /* + * Undo the effect of get_next_timer_interrupt() called from + * tick_nohz_next_event(). + */ + timer_clear_idle(); +} + +/** + * tick_nohz_idle_enter - prepare for entering idle on the current CPU + * + * Called when we start the idle loop. + */ +void tick_nohz_idle_enter(void) +{ + struct tick_sched *ts; + + lockdep_assert_irqs_enabled(); + + local_irq_disable(); + + ts = this_cpu_ptr(&tick_cpu_sched); + + WARN_ON_ONCE(ts->timer_expires_base); + + ts->inidle = 1; + tick_nohz_start_idle(ts); + + local_irq_enable(); +} + +/** + * tick_nohz_irq_exit - update next tick event from interrupt exit + * + * When an interrupt fires while we are idle and it doesn't cause + * a reschedule, it may still add, modify or delete a timer, enqueue + * an RCU callback, etc... + * So we need to re-calculate and reprogram the next tick event. + */ +void tick_nohz_irq_exit(void) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + + if (ts->inidle) + tick_nohz_start_idle(ts); + else + tick_nohz_full_update_tick(ts); +} + +/** + * tick_nohz_idle_got_tick - Check whether or not the tick handler has run + */ +bool tick_nohz_idle_got_tick(void) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + + if (ts->got_idle_tick) { + ts->got_idle_tick = 0; + return true; + } + return false; +} + +/** + * tick_nohz_get_next_hrtimer - return the next expiration time for the hrtimer + * or the tick, whatever that expires first. Note that, if the tick has been + * stopped, it returns the next hrtimer. + * + * Called from power state control code with interrupts disabled + */ +ktime_t tick_nohz_get_next_hrtimer(void) +{ + return __this_cpu_read(tick_cpu_device.evtdev)->next_event; +} + +/** + * tick_nohz_get_sleep_length - return the expected length of the current sleep + * @delta_next: duration until the next event if the tick cannot be stopped + * + * Called from power state control code with interrupts disabled. + * + * The return value of this function and/or the value returned by it through the + * @delta_next pointer can be negative which must be taken into account by its + * callers. + */ +ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next) +{ + struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + int cpu = smp_processor_id(); + /* + * The idle entry time is expected to be a sufficient approximation of + * the current time at this point. + */ + ktime_t now = ts->idle_entrytime; + ktime_t next_event; + + WARN_ON_ONCE(!ts->inidle); + + *delta_next = ktime_sub(dev->next_event, now); + + if (!can_stop_idle_tick(cpu, ts)) + return *delta_next; + + next_event = tick_nohz_next_event(ts, cpu); + if (!next_event) + return *delta_next; + + /* + * If the next highres timer to expire is earlier than next_event, the + * idle governor needs to know that. + */ + next_event = min_t(u64, next_event, + hrtimer_next_event_without(&ts->sched_timer)); + + return ktime_sub(next_event, now); +} + +/** + * tick_nohz_get_idle_calls_cpu - return the current idle calls counter value + * for a particular CPU. + * + * Called from the schedutil frequency scaling governor in scheduler context. + */ +unsigned long tick_nohz_get_idle_calls_cpu(int cpu) +{ + struct tick_sched *ts = tick_get_tick_sched(cpu); + + return ts->idle_calls; +} + +/** + * tick_nohz_get_idle_calls - return the current idle calls counter value + * + * Called from the schedutil frequency scaling governor in scheduler context. + */ +unsigned long tick_nohz_get_idle_calls(void) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + + return ts->idle_calls; +} + +static void tick_nohz_account_idle_time(struct tick_sched *ts, + ktime_t now) +{ + unsigned long ticks; + + ts->idle_exittime = now; + + if (vtime_accounting_enabled_this_cpu()) + return; + /* + * We stopped the tick in idle. Update process times would miss the + * time we slept as update_process_times does only a 1 tick + * accounting. Enforce that this is accounted to idle ! + */ + ticks = jiffies - ts->idle_jiffies; + /* + * We might be one off. Do not randomly account a huge number of ticks! + */ + if (ticks && ticks < LONG_MAX) + account_idle_ticks(ticks); +} + +void tick_nohz_idle_restart_tick(void) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + + if (ts->tick_stopped) { + ktime_t now = ktime_get(); + tick_nohz_restart_sched_tick(ts, now); + tick_nohz_account_idle_time(ts, now); + } +} + +static void tick_nohz_idle_update_tick(struct tick_sched *ts, ktime_t now) +{ + if (tick_nohz_full_cpu(smp_processor_id())) + __tick_nohz_full_update_tick(ts, now); + else + tick_nohz_restart_sched_tick(ts, now); + + tick_nohz_account_idle_time(ts, now); +} + +/** + * tick_nohz_idle_exit - restart the idle tick from the idle task + * + * Restart the idle tick when the CPU is woken up from idle + * This also exit the RCU extended quiescent state. The CPU + * can use RCU again after this function is called. + */ +void tick_nohz_idle_exit(void) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + bool idle_active, tick_stopped; + ktime_t now; + + local_irq_disable(); + + WARN_ON_ONCE(!ts->inidle); + WARN_ON_ONCE(ts->timer_expires_base); + + ts->inidle = 0; + idle_active = ts->idle_active; + tick_stopped = ts->tick_stopped; + + if (idle_active || tick_stopped) + now = ktime_get(); + + if (idle_active) + tick_nohz_stop_idle(ts, now); + + if (tick_stopped) + tick_nohz_idle_update_tick(ts, now); + + local_irq_enable(); +} + +/* + * The nohz low res interrupt handler + */ +static void tick_nohz_handler(struct clock_event_device *dev) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + struct pt_regs *regs = get_irq_regs(); + ktime_t now = ktime_get(); + + dev->next_event = KTIME_MAX; + + tick_sched_do_timer(ts, now); + tick_sched_handle(ts, regs); + + if (unlikely(ts->tick_stopped)) { + /* + * The clockevent device is not reprogrammed, so change the + * clock event device to ONESHOT_STOPPED to avoid spurious + * interrupts on devices which might not be truly one shot. + */ + tick_program_event(KTIME_MAX, 1); + return; + } + + hrtimer_forward(&ts->sched_timer, now, TICK_NSEC); + tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1); +} + +static inline void tick_nohz_activate(struct tick_sched *ts, int mode) +{ + if (!tick_nohz_enabled) + return; + ts->nohz_mode = mode; + /* One update is enough */ + if (!test_and_set_bit(0, &tick_nohz_active)) + timers_update_nohz(); +} + +/** + * tick_nohz_switch_to_nohz - switch to nohz mode + */ +static void tick_nohz_switch_to_nohz(void) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + ktime_t next; + + if (!tick_nohz_enabled) + return; + + if (tick_switch_to_oneshot(tick_nohz_handler)) + return; + + /* + * Recycle the hrtimer in ts, so we can share the + * hrtimer_forward with the highres code. + */ + hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD); + /* Get the next period */ + next = tick_init_jiffy_update(); + + hrtimer_set_expires(&ts->sched_timer, next); + hrtimer_forward_now(&ts->sched_timer, TICK_NSEC); + tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1); + tick_nohz_activate(ts, NOHZ_MODE_LOWRES); +} + +static inline void tick_nohz_irq_enter(void) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + ktime_t now; + + if (!ts->idle_active && !ts->tick_stopped) + return; + now = ktime_get(); + if (ts->idle_active) + tick_nohz_stop_idle(ts, now); + /* + * If all CPUs are idle. We may need to update a stale jiffies value. + * Note nohz_full is a special case: a timekeeper is guaranteed to stay + * alive but it might be busy looping with interrupts disabled in some + * rare case (typically stop machine). So we must make sure we have a + * last resort. + */ + if (ts->tick_stopped) + tick_nohz_update_jiffies(now); +} + +#else + +static inline void tick_nohz_switch_to_nohz(void) { } +static inline void tick_nohz_irq_enter(void) { } +static inline void tick_nohz_activate(struct tick_sched *ts, int mode) { } + +#endif /* CONFIG_NO_HZ_COMMON */ + +/* + * Called from irq_enter to notify about the possible interruption of idle() + */ +void tick_irq_enter(void) +{ + tick_check_oneshot_broadcast_this_cpu(); + tick_nohz_irq_enter(); +} + +/* + * High resolution timer specific code + */ +#ifdef CONFIG_HIGH_RES_TIMERS +/* + * We rearm the timer until we get disabled by the idle code. + * Called with interrupts disabled. + */ +static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) +{ + struct tick_sched *ts = + container_of(timer, struct tick_sched, sched_timer); + struct pt_regs *regs = get_irq_regs(); + ktime_t now = ktime_get(); + + tick_sched_do_timer(ts, now); + + /* + * Do not call, when we are not in irq context and have + * no valid regs pointer + */ + if (regs) + tick_sched_handle(ts, regs); + else + ts->next_tick = 0; + + /* No need to reprogram if we are in idle or full dynticks mode */ + if (unlikely(ts->tick_stopped)) + return HRTIMER_NORESTART; + + hrtimer_forward(timer, now, TICK_NSEC); + + return HRTIMER_RESTART; +} + +static int sched_skew_tick; + +static int __init skew_tick(char *str) +{ + get_option(&str, &sched_skew_tick); + + return 0; +} +early_param("skew_tick", skew_tick); + +/** + * tick_setup_sched_timer - setup the tick emulation timer + */ +void tick_setup_sched_timer(void) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + ktime_t now = ktime_get(); + + /* + * Emulate tick processing via per-CPU hrtimers: + */ + hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD); + ts->sched_timer.function = tick_sched_timer; + + /* Get the next period (per-CPU) */ + hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update()); + + /* Offset the tick to avert jiffies_lock contention. */ + if (sched_skew_tick) { + u64 offset = TICK_NSEC >> 1; + do_div(offset, num_possible_cpus()); + offset *= smp_processor_id(); + hrtimer_add_expires_ns(&ts->sched_timer, offset); + } + + hrtimer_forward(&ts->sched_timer, now, TICK_NSEC); + hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD); + tick_nohz_activate(ts, NOHZ_MODE_HIGHRES); +} +#endif /* HIGH_RES_TIMERS */ + +#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS +void tick_cancel_sched_timer(int cpu) +{ + struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); + ktime_t idle_sleeptime, iowait_sleeptime; + unsigned long idle_calls, idle_sleeps; + +# ifdef CONFIG_HIGH_RES_TIMERS + if (ts->sched_timer.base) + hrtimer_cancel(&ts->sched_timer); +# endif + + idle_sleeptime = ts->idle_sleeptime; + iowait_sleeptime = ts->iowait_sleeptime; + idle_calls = ts->idle_calls; + idle_sleeps = ts->idle_sleeps; + memset(ts, 0, sizeof(*ts)); + ts->idle_sleeptime = idle_sleeptime; + ts->iowait_sleeptime = iowait_sleeptime; + ts->idle_calls = idle_calls; + ts->idle_sleeps = idle_sleeps; +} +#endif + +/* + * Async notification about clocksource changes + */ +void tick_clock_notify(void) +{ + int cpu; + + for_each_possible_cpu(cpu) + set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks); +} + +/* + * Async notification about clock event changes + */ +void tick_oneshot_notify(void) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + + set_bit(0, &ts->check_clocks); +} + +/* + * Check, if a change happened, which makes oneshot possible. + * + * Called cyclic from the hrtimer softirq (driven by the timer + * softirq) allow_nohz signals, that we can switch into low-res nohz + * mode, because high resolution timers are disabled (either compile + * or runtime). Called with interrupts disabled. + */ +int tick_check_oneshot_change(int allow_nohz) +{ + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + + if (!test_and_clear_bit(0, &ts->check_clocks)) + return 0; + + if (ts->nohz_mode != NOHZ_MODE_INACTIVE) + return 0; + + if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available()) + return 0; + + if (!allow_nohz) + return 1; + + tick_nohz_switch_to_nohz(); + return 0; +} |