v4.19.13 snapshot.
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
new file mode 100644
index 0000000..5b33e2f
--- /dev/null
+++ b/kernel/time/tick-sched.c
@@ -0,0 +1,1389 @@
+/*
+ * linux/kernel/time/tick-sched.c
+ *
+ * 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
+ *
+ * Distribute under GPLv2.
+ */
+#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 (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)
+ && !tick_nohz_full_cpu(cpu))
+ 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 boot 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;
+ }
+
+ 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() && cpu_online(cpu))) {
+ 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,
+ */
+ if (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;
+}