// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
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* Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
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* Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner
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*
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* No idle tick implementation for low and high resolution timers
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*
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* Started by: Thomas Gleixner and Ingo Molnar
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*/
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#include <linux/cpu.h>
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#include <linux/err.h>
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#include <linux/hrtimer.h>
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#include <linux/interrupt.h>
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#include <linux/kernel_stat.h>
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#include <linux/percpu.h>
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#include <linux/nmi.h>
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#include <linux/profile.h>
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#include <linux/sched/signal.h>
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#include <linux/sched/clock.h>
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#include <linux/sched/stat.h>
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#include <linux/sched/nohz.h>
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#include <linux/module.h>
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#include <linux/irq_work.h>
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#include <linux/posix-timers.h>
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#include <linux/context_tracking.h>
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#include <linux/mm.h>
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#include <trace/hooks/sched.h>
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#include <asm/irq_regs.h>
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#include "tick-internal.h"
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#include <trace/events/timer.h>
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/*
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* Per-CPU nohz control structure
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*/
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static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
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struct tick_sched *tick_get_tick_sched(int cpu)
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{
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return &per_cpu(tick_cpu_sched, cpu);
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}
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#if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS)
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/*
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* The time, when the last jiffy update happened. Protected by jiffies_lock.
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*/
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static ktime_t last_jiffies_update;
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/*
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* Must be called with interrupts disabled !
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*/
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static void tick_do_update_jiffies64(ktime_t now)
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{
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unsigned long ticks = 0;
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ktime_t delta;
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/*
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* Do a quick check without holding jiffies_lock:
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* The READ_ONCE() pairs with two updates done later in this function.
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*/
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delta = ktime_sub(now, READ_ONCE(last_jiffies_update));
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if (delta < tick_period)
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return;
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/* Reevaluate with jiffies_lock held */
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raw_spin_lock(&jiffies_lock);
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write_seqcount_begin(&jiffies_seq);
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delta = ktime_sub(now, last_jiffies_update);
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if (delta >= tick_period) {
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delta = ktime_sub(delta, tick_period);
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/* Pairs with the lockless read in this function. */
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WRITE_ONCE(last_jiffies_update,
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ktime_add(last_jiffies_update, tick_period));
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/* Slow path for long timeouts */
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if (unlikely(delta >= tick_period)) {
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s64 incr = ktime_to_ns(tick_period);
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ticks = ktime_divns(delta, incr);
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/* Pairs with the lockless read in this function. */
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WRITE_ONCE(last_jiffies_update,
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ktime_add_ns(last_jiffies_update,
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incr * ticks));
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}
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do_timer(++ticks);
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/* Keep the tick_next_period variable up to date */
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tick_next_period = ktime_add(last_jiffies_update, tick_period);
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} else {
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write_seqcount_end(&jiffies_seq);
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raw_spin_unlock(&jiffies_lock);
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return;
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}
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write_seqcount_end(&jiffies_seq);
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raw_spin_unlock(&jiffies_lock);
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update_wall_time();
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}
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/*
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* Initialize and return retrieve the jiffies update.
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*/
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static ktime_t tick_init_jiffy_update(void)
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{
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ktime_t period;
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raw_spin_lock(&jiffies_lock);
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write_seqcount_begin(&jiffies_seq);
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/* Did we start the jiffies update yet ? */
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if (last_jiffies_update == 0)
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last_jiffies_update = tick_next_period;
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period = last_jiffies_update;
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write_seqcount_end(&jiffies_seq);
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raw_spin_unlock(&jiffies_lock);
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return period;
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}
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static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
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{
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int cpu = smp_processor_id();
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#ifdef CONFIG_NO_HZ_COMMON
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/*
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* Check if the do_timer duty was dropped. We don't care about
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* concurrency: This happens only when the CPU in charge went
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* into a long sleep. If two CPUs happen to assign themselves to
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* this duty, then the jiffies update is still serialized by
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* jiffies_lock.
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*
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* If nohz_full is enabled, this should not happen because the
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* tick_do_timer_cpu never relinquishes.
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*/
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if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) {
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#ifdef CONFIG_NO_HZ_FULL
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WARN_ON_ONCE(tick_nohz_full_running);
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#endif
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tick_do_timer_cpu = cpu;
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}
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#endif
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/* Check, if the jiffies need an update */
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if (tick_do_timer_cpu == cpu) {
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tick_do_update_jiffies64(now);
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trace_android_vh_jiffies_update(NULL);
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}
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if (ts->inidle)
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ts->got_idle_tick = 1;
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}
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static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
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{
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#ifdef CONFIG_NO_HZ_COMMON
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/*
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* When we are idle and the tick is stopped, we have to touch
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* the watchdog as we might not schedule for a really long
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* time. This happens on complete idle SMP systems while
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* waiting on the login prompt. We also increment the "start of
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* idle" jiffy stamp so the idle accounting adjustment we do
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* when we go busy again does not account too much ticks.
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*/
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if (ts->tick_stopped) {
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touch_softlockup_watchdog_sched();
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if (is_idle_task(current))
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ts->idle_jiffies++;
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/*
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* In case the current tick fired too early past its expected
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* expiration, make sure we don't bypass the next clock reprogramming
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* to the same deadline.
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*/
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ts->next_tick = 0;
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}
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#endif
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update_process_times(user_mode(regs));
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profile_tick(CPU_PROFILING);
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}
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#endif
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#ifdef CONFIG_NO_HZ_FULL
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cpumask_var_t tick_nohz_full_mask;
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bool tick_nohz_full_running;
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EXPORT_SYMBOL_GPL(tick_nohz_full_running);
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static atomic_t tick_dep_mask;
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static bool check_tick_dependency(atomic_t *dep)
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{
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int val = atomic_read(dep);
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if (val & TICK_DEP_MASK_POSIX_TIMER) {
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trace_tick_stop(0, TICK_DEP_MASK_POSIX_TIMER);
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return true;
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}
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if (val & TICK_DEP_MASK_PERF_EVENTS) {
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trace_tick_stop(0, TICK_DEP_MASK_PERF_EVENTS);
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return true;
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}
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if (val & TICK_DEP_MASK_SCHED) {
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trace_tick_stop(0, TICK_DEP_MASK_SCHED);
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return true;
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}
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if (val & TICK_DEP_MASK_CLOCK_UNSTABLE) {
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trace_tick_stop(0, TICK_DEP_MASK_CLOCK_UNSTABLE);
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return true;
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}
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if (val & TICK_DEP_MASK_RCU) {
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trace_tick_stop(0, TICK_DEP_MASK_RCU);
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return true;
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}
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return false;
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}
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static bool can_stop_full_tick(int cpu, struct tick_sched *ts)
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{
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lockdep_assert_irqs_disabled();
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if (unlikely(!cpu_online(cpu)))
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return false;
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if (check_tick_dependency(&tick_dep_mask))
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return false;
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if (check_tick_dependency(&ts->tick_dep_mask))
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return false;
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if (check_tick_dependency(¤t->tick_dep_mask))
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return false;
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if (check_tick_dependency(¤t->signal->tick_dep_mask))
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return false;
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return true;
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}
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static void nohz_full_kick_func(struct irq_work *work)
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{
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/* Empty, the tick restart happens on tick_nohz_irq_exit() */
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}
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static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
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.func = nohz_full_kick_func,
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.flags = ATOMIC_INIT(IRQ_WORK_HARD_IRQ),
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};
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/*
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* Kick this CPU if it's full dynticks in order to force it to
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* re-evaluate its dependency on the tick and restart it if necessary.
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* This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(),
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* is NMI safe.
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*/
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static void tick_nohz_full_kick(void)
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{
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if (!tick_nohz_full_cpu(smp_processor_id()))
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return;
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irq_work_queue(this_cpu_ptr(&nohz_full_kick_work));
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}
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/*
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* Kick the CPU if it's full dynticks in order to force it to
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* re-evaluate its dependency on the tick and restart it if necessary.
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*/
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void tick_nohz_full_kick_cpu(int cpu)
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{
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if (!tick_nohz_full_cpu(cpu))
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return;
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irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu);
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}
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/*
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* Kick all full dynticks CPUs in order to force these to re-evaluate
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* their dependency on the tick and restart it if necessary.
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*/
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static void tick_nohz_full_kick_all(void)
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{
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int cpu;
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if (!tick_nohz_full_running)
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return;
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preempt_disable();
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for_each_cpu_and(cpu, tick_nohz_full_mask, cpu_online_mask)
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tick_nohz_full_kick_cpu(cpu);
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preempt_enable();
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}
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static void tick_nohz_dep_set_all(atomic_t *dep,
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enum tick_dep_bits bit)
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{
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int prev;
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prev = atomic_fetch_or(BIT(bit), dep);
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if (!prev)
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tick_nohz_full_kick_all();
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}
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/*
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* Set a global tick dependency. Used by perf events that rely on freq and
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* by unstable clock.
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*/
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void tick_nohz_dep_set(enum tick_dep_bits bit)
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{
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tick_nohz_dep_set_all(&tick_dep_mask, bit);
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}
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void tick_nohz_dep_clear(enum tick_dep_bits bit)
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{
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atomic_andnot(BIT(bit), &tick_dep_mask);
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}
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/*
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* Set per-CPU tick dependency. Used by scheduler and perf events in order to
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* manage events throttling.
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*/
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void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit)
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{
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int prev;
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struct tick_sched *ts;
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ts = per_cpu_ptr(&tick_cpu_sched, cpu);
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prev = atomic_fetch_or(BIT(bit), &ts->tick_dep_mask);
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if (!prev) {
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preempt_disable();
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/* Perf needs local kick that is NMI safe */
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if (cpu == smp_processor_id()) {
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tick_nohz_full_kick();
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} else {
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/* Remote irq work not NMI-safe */
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if (!WARN_ON_ONCE(in_nmi()))
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tick_nohz_full_kick_cpu(cpu);
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}
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preempt_enable();
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}
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}
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EXPORT_SYMBOL_GPL(tick_nohz_dep_set_cpu);
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void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit)
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{
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struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
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atomic_andnot(BIT(bit), &ts->tick_dep_mask);
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}
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EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_cpu);
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/*
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* Set a per-task tick dependency. RCU need this. Also posix CPU timers
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* in order to elapse per task timers.
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*/
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void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit)
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{
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if (!atomic_fetch_or(BIT(bit), &tsk->tick_dep_mask)) {
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if (tsk == current) {
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preempt_disable();
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tick_nohz_full_kick();
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preempt_enable();
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} else {
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/*
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* Some future tick_nohz_full_kick_task()
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* should optimize this.
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*/
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tick_nohz_full_kick_all();
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}
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}
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}
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EXPORT_SYMBOL_GPL(tick_nohz_dep_set_task);
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void tick_nohz_dep_clear_task(struct task_struct *tsk, enum tick_dep_bits bit)
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{
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atomic_andnot(BIT(bit), &tsk->tick_dep_mask);
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}
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EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_task);
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/*
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* Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse
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* per process timers.
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*/
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void tick_nohz_dep_set_signal(struct signal_struct *sig, enum tick_dep_bits bit)
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{
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tick_nohz_dep_set_all(&sig->tick_dep_mask, bit);
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}
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void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bit)
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{
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atomic_andnot(BIT(bit), &sig->tick_dep_mask);
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}
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/*
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* Re-evaluate the need for the tick as we switch the current task.
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* It might need the tick due to per task/process properties:
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* perf events, posix CPU timers, ...
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*/
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void __tick_nohz_task_switch(void)
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{
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unsigned long flags;
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struct tick_sched *ts;
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local_irq_save(flags);
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if (!tick_nohz_full_cpu(smp_processor_id()))
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goto out;
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ts = this_cpu_ptr(&tick_cpu_sched);
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if (ts->tick_stopped) {
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if (atomic_read(¤t->tick_dep_mask) ||
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atomic_read(¤t->signal->tick_dep_mask))
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tick_nohz_full_kick();
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}
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out:
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local_irq_restore(flags);
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}
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/* Get the boot-time nohz CPU list from the kernel parameters. */
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void __init tick_nohz_full_setup(cpumask_var_t cpumask)
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{
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alloc_bootmem_cpumask_var(&tick_nohz_full_mask);
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cpumask_copy(tick_nohz_full_mask, cpumask);
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tick_nohz_full_running = true;
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}
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static int tick_nohz_cpu_down(unsigned int cpu)
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{
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/*
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* The tick_do_timer_cpu CPU handles housekeeping duty (unbound
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* timers, workqueues, timekeeping, ...) on behalf of full dynticks
|
* CPUs. It must remain online when nohz full is enabled.
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*/
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if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
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return -EBUSY;
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return 0;
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}
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void __init tick_nohz_init(void)
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{
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int cpu, ret;
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if (!tick_nohz_full_running)
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return;
|
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/*
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* 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
|
*/
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if (!arch_irq_work_has_interrupt()) {
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pr_warn("NO_HZ: Can't run full dynticks because arch doesn't support irq work self-IPIs\n");
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cpumask_clear(tick_nohz_full_mask);
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tick_nohz_full_running = false;
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return;
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}
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if (IS_ENABLED(CONFIG_PM_SLEEP_SMP) &&
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!IS_ENABLED(CONFIG_PM_SLEEP_SMP_NONZERO_CPU)) {
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cpu = smp_processor_id();
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if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) {
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pr_warn("NO_HZ: Clearing %d from nohz_full range "
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"for timekeeping\n", cpu);
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cpumask_clear_cpu(cpu, tick_nohz_full_mask);
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}
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}
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for_each_cpu(cpu, tick_nohz_full_mask)
|
context_tracking_cpu_set(cpu);
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ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
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"kernel/nohz:predown", NULL,
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tick_nohz_cpu_down);
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WARN_ON(ret < 0);
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pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n",
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cpumask_pr_args(tick_nohz_full_mask));
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}
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#endif
|
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/*
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* NOHZ - aka dynamic tick functionality
|
*/
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#ifdef CONFIG_NO_HZ_COMMON
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/*
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* NO HZ enabled ?
|
*/
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bool tick_nohz_enabled __read_mostly = true;
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unsigned long tick_nohz_active __read_mostly;
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/*
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* Enable / Disable tickless mode
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*/
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static int __init setup_tick_nohz(char *str)
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{
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return (kstrtobool(str, &tick_nohz_enabled) == 0);
|
}
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__setup("nohz=", setup_tick_nohz);
|
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bool tick_nohz_tick_stopped(void)
|
{
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struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
return ts->tick_stopped;
|
}
|
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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_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, next_tmr, next_rcu, 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
|
* 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();
|
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_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;
|
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_bh_blocked() &&
|
(local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) {
|
pr_warn("NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #%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;
|
|
/* 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_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
|
*/
|
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);
|
}
|
EXPORT_SYMBOL_GPL(tick_nohz_get_sleep_length);
|
|
/**
|
* 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;
|
}
|
EXPORT_SYMBOL_GPL(tick_nohz_get_idle_calls_cpu);
|
|
/**
|
* 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_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);
|
#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_HARD);
|
/* 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_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 = 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_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);
|
|
# 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;
|
}
|
