| // 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/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. Protected by jiffies_lock. |
| */ |
| static ktime_t last_jiffies_update; |
| |
| /* |
| * Must be called with interrupts disabled ! |
| */ |
| static void tick_do_update_jiffies64(ktime_t now) |
| { |
| unsigned long ticks = 0; |
| ktime_t delta; |
| |
| /* |
| * Do a quick check without holding jiffies_lock: |
| */ |
| delta = ktime_sub(now, last_jiffies_update); |
| if (delta < tick_period) |
| return; |
| |
| /* Reevaluate with jiffies_lock held */ |
| write_seqlock(&jiffies_lock); |
| |
| delta = ktime_sub(now, last_jiffies_update); |
| if (delta >= tick_period) { |
| |
| delta = ktime_sub(delta, tick_period); |
| last_jiffies_update = ktime_add(last_jiffies_update, |
| tick_period); |
| |
| /* Slow path for long timeouts */ |
| if (unlikely(delta >= tick_period)) { |
| s64 incr = ktime_to_ns(tick_period); |
| |
| ticks = ktime_divns(delta, incr); |
| |
| last_jiffies_update = ktime_add_ns(last_jiffies_update, |
| incr * ticks); |
| } |
| do_timer(++ticks); |
| |
| /* Keep the tick_next_period variable up to date */ |
| tick_next_period = ktime_add(last_jiffies_update, tick_period); |
| } else { |
| write_sequnlock(&jiffies_lock); |
| return; |
| } |
| write_sequnlock(&jiffies_lock); |
| update_wall_time(); |
| } |
| |
| /* |
| * Initialize and return retrieve the jiffies update. |
| */ |
| static ktime_t tick_init_jiffy_update(void) |
| { |
| ktime_t period; |
| |
| write_seqlock(&jiffies_lock); |
| /* Did we start the jiffies update yet ? */ |
| if (last_jiffies_update == 0) |
| last_jiffies_update = tick_next_period; |
| period = last_jiffies_update; |
| write_sequnlock(&jiffies_lock); |
| return period; |
| } |
| |
| 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(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 (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; |
| bool 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; |
| } |
| |
| 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) = { |
| .func = 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); |
| } |
| |
| /* |
| * 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(); |
| } |
| } |
| |
| 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); |
| } |
| |
| /* |
| * Set a per-task tick dependency. Posix CPU timers need this in order to elapse |
| * per task timers. |
| */ |
| void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit) |
| { |
| /* |
| * We could optimize this with just kicking the target running the task |
| * if that noise matters for nohz full users. |
| */ |
| tick_nohz_dep_set_all(&tsk->tick_dep_mask, bit); |
| } |
| |
| void tick_nohz_dep_clear_task(struct task_struct *tsk, enum tick_dep_bits bit) |
| { |
| atomic_andnot(BIT(bit), &tsk->tick_dep_mask); |
| } |
| |
| /* |
| * 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 signal_struct *sig, enum tick_dep_bits bit) |
| { |
| tick_nohz_dep_set_all(&sig->tick_dep_mask, bit); |
| } |
| |
| 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) |
| { |
| unsigned long flags; |
| struct tick_sched *ts; |
| |
| local_irq_save(flags); |
| |
| if (!tick_nohz_full_cpu(smp_processor_id())) |
| goto out; |
| |
| 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(); |
| } |
| out: |
| local_irq_restore(flags); |
| } |
| |
| /* 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; |
| } |
| |
| static int tick_nohz_cpu_down(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 -EBUSY; |
| return 0; |
| } |
| |
| 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) |
| context_tracking_cpu_set(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(); |
| } |
| |
| /* |
| * Updates the per-CPU time idle statistics counters |
| */ |
| static void |
| update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time) |
| { |
| ktime_t delta; |
| |
| if (ts->idle_active) { |
| delta = ktime_sub(now, ts->idle_entrytime); |
| if (nr_iowait_cpu(cpu) > 0) |
| ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta); |
| else |
| ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); |
| ts->idle_entrytime = now; |
| } |
| |
| if (last_update_time) |
| *last_update_time = ktime_to_us(now); |
| |
| } |
| |
| static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now) |
| { |
| update_ts_time_stats(smp_processor_id(), ts, now, NULL); |
| ts->idle_active = 0; |
| |
| sched_clock_idle_wakeup_event(); |
| } |
| |
| static void tick_nohz_start_idle(struct tick_sched *ts) |
| { |
| ts->idle_entrytime = ktime_get(); |
| ts->idle_active = 1; |
| sched_clock_idle_sleep_event(); |
| } |
| |
| /** |
| * 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. |
| * |
| * 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); |
| ktime_t now, idle; |
| |
| if (!tick_nohz_active) |
| return -1; |
| |
| now = ktime_get(); |
| if (last_update_time) { |
| update_ts_time_stats(cpu, ts, now, last_update_time); |
| idle = ts->idle_sleeptime; |
| } else { |
| if (ts->idle_active && !nr_iowait_cpu(cpu)) { |
| ktime_t delta = ktime_sub(now, ts->idle_entrytime); |
| |
| idle = ktime_add(ts->idle_sleeptime, delta); |
| } else { |
| idle = ts->idle_sleeptime; |
| } |
| } |
| |
| return ktime_to_us(idle); |
| |
| } |
| 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. |
| * |
| * 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); |
| ktime_t now, iowait; |
| |
| if (!tick_nohz_active) |
| return -1; |
| |
| now = ktime_get(); |
| if (last_update_time) { |
| update_ts_time_stats(cpu, ts, now, last_update_time); |
| iowait = ts->iowait_sleeptime; |
| } else { |
| if (ts->idle_active && nr_iowait_cpu(cpu) > 0) { |
| ktime_t delta = ktime_sub(now, ts->idle_entrytime); |
| |
| iowait = ktime_add(ts->iowait_sleeptime, delta); |
| } else { |
| iowait = ts->iowait_sleeptime; |
| } |
| } |
| |
| return ktime_to_us(iowait); |
| } |
| 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_period); |
| |
| if (ts->nohz_mode == NOHZ_MODE_HIGHRES) |
| hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED); |
| 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, next_tmr, next_rcu, delta, expires; |
| unsigned long seq, basejiff; |
| |
| /* Read jiffies and the time when jiffies were updated last */ |
| do { |
| seq = read_seqbegin(&jiffies_lock); |
| basemono = last_jiffies_update; |
| basejiff = jiffies; |
| } while (read_seqretry(&jiffies_lock, 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 |
| * immeditate 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(basemono, &next_rcu) || 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_tmr = get_next_timer_interrupt(basejiff, basemono); |
| ts->next_timer = next_tmr; |
| /* Take the next rcu event into account */ |
| next_tick = next_rcu < next_tmr ? next_rcu : next_tmr; |
| } |
| |
| /* |
| * 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(); |
| cpu_load_update_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); |
| return; |
| } |
| |
| if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
| hrtimer_start(&ts->sched_timer, tick, HRTIMER_MODE_ABS_PINNED); |
| } 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); |
| cpu_load_update_nohz_stop(); |
| |
| /* |
| * 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; |
| ts->idle_exittime = now; |
| |
| tick_nohz_restart(ts, now); |
| } |
| |
| static void tick_nohz_full_update_tick(struct tick_sched *ts) |
| { |
| #ifdef CONFIG_NO_HZ_FULL |
| int cpu = smp_processor_id(); |
| |
| if (!tick_nohz_full_cpu(cpu)) |
| return; |
| |
| if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) |
| return; |
| |
| 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, ktime_get()); |
| #endif |
| } |
| |
| 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(local_softirq_pending())) { |
| static int ratelimit; |
| |
| if (ratelimit < 10 && |
| (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) { |
| pr_warn("NOHZ: local_softirq_pending %02x\n", |
| (unsigned int) local_softirq_pending()); |
| ratelimit++; |
| } |
| 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; |
| /* |
| * 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 (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; |
| } |
| |
| return true; |
| } |
| |
| static void __tick_nohz_idle_stop_tick(struct tick_sched *ts) |
| { |
| ktime_t expires; |
| int cpu = smp_processor_id(); |
| |
| /* |
| * 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); |
| } |
| } |
| |
| /** |
| * 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) |
| { |
| __tick_nohz_idle_stop_tick(this_cpu_ptr(&tick_cpu_sched)); |
| } |
| |
| 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_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 |
| */ |
| 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_ticks(struct tick_sched *ts) |
| { |
| #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE |
| unsigned long ticks; |
| |
| if (vtime_accounting_cpu_enabled()) |
| 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); |
| #endif |
| } |
| |
| static void __tick_nohz_idle_restart_tick(struct tick_sched *ts, ktime_t now) |
| { |
| tick_nohz_restart_sched_tick(ts, now); |
| tick_nohz_account_idle_ticks(ts); |
| } |
| |
| void tick_nohz_idle_restart_tick(void) |
| { |
| struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| |
| if (ts->tick_stopped) |
| __tick_nohz_idle_restart_tick(ts, ktime_get()); |
| } |
| |
| /** |
| * 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_restart_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); |
| |
| /* No need to reprogram if we are running tickless */ |
| if (unlikely(ts->tick_stopped)) |
| return; |
| |
| hrtimer_forward(&ts->sched_timer, now, tick_period); |
| 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); |
| /* Get the next period */ |
| next = tick_init_jiffy_update(); |
| |
| hrtimer_set_expires(&ts->sched_timer, next); |
| hrtimer_forward_now(&ts->sched_timer, tick_period); |
| 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 (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_period); |
| |
| 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); |
| 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 = ktime_to_ns(tick_period) >> 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_period); |
| hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED); |
| 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); |
| |
| # ifdef CONFIG_HIGH_RES_TIMERS |
| if (ts->sched_timer.base) |
| hrtimer_cancel(&ts->sched_timer); |
| # endif |
| |
| memset(ts, 0, sizeof(*ts)); |
| } |
| #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; |
| } |