// SPDX-License-Identifier: GPL-2.0
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/*
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* This file contains the base functions to manage periodic tick
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* related events.
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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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#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/nmi.h>
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#include <linux/percpu.h>
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#include <linux/profile.h>
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#include <linux/sched.h>
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#include <linux/module.h>
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#include <trace/events/power.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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/*
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* Tick devices
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*/
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DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
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/*
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* Tick next event: keeps track of the tick time
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*/
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ktime_t tick_next_period;
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ktime_t tick_period;
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/*
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* tick_do_timer_cpu is a timer core internal variable which holds the CPU NR
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* which is responsible for calling do_timer(), i.e. the timekeeping stuff. This
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* variable has two functions:
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*
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* 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the
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* timekeeping lock all at once. Only the CPU which is assigned to do the
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* update is handling it.
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*
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* 2) Hand off the duty in the NOHZ idle case by setting the value to
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* TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks
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* at it will take over and keep the time keeping alive. The handover
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* procedure also covers cpu hotplug.
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*/
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int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
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#ifdef CONFIG_NO_HZ_FULL
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/*
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* tick_do_timer_boot_cpu indicates the boot CPU temporarily owns
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* tick_do_timer_cpu and it should be taken over by an eligible secondary
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* when one comes online.
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*/
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static int tick_do_timer_boot_cpu __read_mostly = -1;
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#endif
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/*
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* Debugging: see timer_list.c
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*/
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struct tick_device *tick_get_device(int cpu)
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{
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return &per_cpu(tick_cpu_device, cpu);
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}
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/**
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* tick_is_oneshot_available - check for a oneshot capable event device
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*/
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int tick_is_oneshot_available(void)
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{
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struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
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if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
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return 0;
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if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
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return 1;
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return tick_broadcast_oneshot_available();
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}
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/*
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* Periodic tick
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*/
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static void tick_periodic(int cpu)
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{
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if (tick_do_timer_cpu == cpu) {
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raw_spin_lock(&jiffies_lock);
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write_seqcount_begin(&jiffies_seq);
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/* Keep track of the next tick event */
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tick_next_period = ktime_add(tick_next_period, tick_period);
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do_timer(1);
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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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trace_android_vh_jiffies_update(NULL);
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}
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update_process_times(user_mode(get_irq_regs()));
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profile_tick(CPU_PROFILING);
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}
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/*
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* Event handler for periodic ticks
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*/
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void tick_handle_periodic(struct clock_event_device *dev)
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{
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int cpu = smp_processor_id();
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ktime_t next = dev->next_event;
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tick_periodic(cpu);
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#if defined(CONFIG_HIGH_RES_TIMERS) || defined(CONFIG_NO_HZ_COMMON)
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/*
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* The cpu might have transitioned to HIGHRES or NOHZ mode via
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* update_process_times() -> run_local_timers() ->
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* hrtimer_run_queues().
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*/
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if (dev->event_handler != tick_handle_periodic)
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return;
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#endif
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if (!clockevent_state_oneshot(dev))
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return;
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for (;;) {
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/*
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* Setup the next period for devices, which do not have
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* periodic mode:
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*/
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next = ktime_add(next, tick_period);
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if (!clockevents_program_event(dev, next, false))
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return;
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/*
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* Have to be careful here. If we're in oneshot mode,
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* before we call tick_periodic() in a loop, we need
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* to be sure we're using a real hardware clocksource.
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* Otherwise we could get trapped in an infinite
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* loop, as the tick_periodic() increments jiffies,
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* which then will increment time, possibly causing
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* the loop to trigger again and again.
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*/
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if (timekeeping_valid_for_hres())
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tick_periodic(cpu);
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}
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}
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/*
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* Setup the device for a periodic tick
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*/
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void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
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{
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tick_set_periodic_handler(dev, broadcast);
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/* Broadcast setup ? */
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if (!tick_device_is_functional(dev))
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return;
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if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
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!tick_broadcast_oneshot_active()) {
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clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
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} else {
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unsigned int seq;
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ktime_t next;
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do {
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seq = read_seqcount_begin(&jiffies_seq);
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next = tick_next_period;
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} while (read_seqcount_retry(&jiffies_seq, seq));
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clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
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for (;;) {
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if (!clockevents_program_event(dev, next, false))
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return;
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next = ktime_add(next, tick_period);
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}
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}
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}
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#ifdef CONFIG_NO_HZ_FULL
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static void giveup_do_timer(void *info)
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{
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int cpu = *(unsigned int *)info;
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WARN_ON(tick_do_timer_cpu != smp_processor_id());
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tick_do_timer_cpu = cpu;
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}
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static void tick_take_do_timer_from_boot(void)
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{
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int cpu = smp_processor_id();
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int from = tick_do_timer_boot_cpu;
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if (from >= 0 && from != cpu)
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smp_call_function_single(from, giveup_do_timer, &cpu, 1);
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}
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#endif
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/*
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* Setup the tick device
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*/
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static void tick_setup_device(struct tick_device *td,
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struct clock_event_device *newdev, int cpu,
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const struct cpumask *cpumask)
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{
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void (*handler)(struct clock_event_device *) = NULL;
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ktime_t next_event = 0;
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/*
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* First device setup ?
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*/
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if (!td->evtdev) {
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/*
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* If no cpu took the do_timer update, assign it to
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* this cpu:
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*/
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if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
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tick_do_timer_cpu = cpu;
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tick_next_period = ktime_get();
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tick_period = NSEC_PER_SEC / HZ;
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#ifdef CONFIG_NO_HZ_FULL
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/*
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* The boot CPU may be nohz_full, in which case set
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* tick_do_timer_boot_cpu so the first housekeeping
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* secondary that comes up will take do_timer from
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* us.
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*/
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if (tick_nohz_full_cpu(cpu))
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tick_do_timer_boot_cpu = cpu;
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} else if (tick_do_timer_boot_cpu != -1 &&
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!tick_nohz_full_cpu(cpu)) {
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tick_take_do_timer_from_boot();
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tick_do_timer_boot_cpu = -1;
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WARN_ON(tick_do_timer_cpu != cpu);
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#endif
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}
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/*
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* Startup in periodic mode first.
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*/
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td->mode = TICKDEV_MODE_PERIODIC;
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} else {
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handler = td->evtdev->event_handler;
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next_event = td->evtdev->next_event;
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td->evtdev->event_handler = clockevents_handle_noop;
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}
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td->evtdev = newdev;
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/*
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* When the device is not per cpu, pin the interrupt to the
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* current cpu:
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*/
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if (!cpumask_equal(newdev->cpumask, cpumask))
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irq_set_affinity(newdev->irq, cpumask);
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/*
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* When global broadcasting is active, check if the current
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* device is registered as a placeholder for broadcast mode.
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* This allows us to handle this x86 misfeature in a generic
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* way. This function also returns !=0 when we keep the
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* current active broadcast state for this CPU.
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*/
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if (tick_device_uses_broadcast(newdev, cpu))
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return;
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if (td->mode == TICKDEV_MODE_PERIODIC)
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tick_setup_periodic(newdev, 0);
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else
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tick_setup_oneshot(newdev, handler, next_event);
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}
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void tick_install_replacement(struct clock_event_device *newdev)
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{
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struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
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int cpu = smp_processor_id();
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clockevents_exchange_device(td->evtdev, newdev);
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tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
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if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
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tick_oneshot_notify();
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}
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static bool tick_check_percpu(struct clock_event_device *curdev,
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struct clock_event_device *newdev, int cpu)
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{
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if (!cpumask_test_cpu(cpu, newdev->cpumask))
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return false;
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if (cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
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return true;
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/* Check if irq affinity can be set */
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if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq))
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return false;
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/* Prefer an existing cpu local device */
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if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
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return false;
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return true;
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}
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static bool tick_check_preferred(struct clock_event_device *curdev,
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struct clock_event_device *newdev)
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{
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/* Prefer oneshot capable device */
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if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) {
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if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT))
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return false;
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if (tick_oneshot_mode_active())
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return false;
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}
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/*
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* Use the higher rated one, but prefer a CPU local device with a lower
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* rating than a non-CPU local device
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*/
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return !curdev ||
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newdev->rating > curdev->rating ||
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!cpumask_equal(curdev->cpumask, newdev->cpumask);
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}
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/*
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* Check whether the new device is a better fit than curdev. curdev
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* can be NULL !
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*/
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bool tick_check_replacement(struct clock_event_device *curdev,
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struct clock_event_device *newdev)
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{
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if (!tick_check_percpu(curdev, newdev, smp_processor_id()))
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return false;
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return tick_check_preferred(curdev, newdev);
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}
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/*
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* Check, if the new registered device should be used. Called with
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* clockevents_lock held and interrupts disabled.
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*/
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void tick_check_new_device(struct clock_event_device *newdev)
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{
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struct clock_event_device *curdev;
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struct tick_device *td;
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int cpu;
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cpu = smp_processor_id();
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td = &per_cpu(tick_cpu_device, cpu);
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curdev = td->evtdev;
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/* cpu local device ? */
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if (!tick_check_percpu(curdev, newdev, cpu))
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goto out_bc;
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/* Preference decision */
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if (!tick_check_preferred(curdev, newdev))
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goto out_bc;
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if (!try_module_get(newdev->owner))
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return;
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/*
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* Replace the eventually existing device by the new
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* device. If the current device is the broadcast device, do
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* not give it back to the clockevents layer !
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*/
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if (tick_is_broadcast_device(curdev)) {
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clockevents_shutdown(curdev);
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curdev = NULL;
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}
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clockevents_exchange_device(curdev, newdev);
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tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
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if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
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tick_oneshot_notify();
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return;
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out_bc:
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/*
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* Can the new device be used as a broadcast device ?
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*/
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tick_install_broadcast_device(newdev, cpu);
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}
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/**
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* tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
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* @state: The target state (enter/exit)
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*
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* The system enters/leaves a state, where affected devices might stop
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* Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
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*
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* Called with interrupts disabled, so clockevents_lock is not
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* required here because the local clock event device cannot go away
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* under us.
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*/
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int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
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{
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struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
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if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))
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return 0;
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return __tick_broadcast_oneshot_control(state);
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}
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EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control);
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#ifdef CONFIG_HOTPLUG_CPU
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/*
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* Transfer the do_timer job away from a dying cpu.
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*
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* Called with interrupts disabled. Not locking required. If
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* tick_do_timer_cpu is owned by this cpu, nothing can change it.
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*/
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void tick_handover_do_timer(void)
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{
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if (tick_do_timer_cpu == smp_processor_id()) {
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int cpu = cpumask_first(cpu_online_mask);
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tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
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TICK_DO_TIMER_NONE;
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}
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}
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/*
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* Shutdown an event device on a given cpu:
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*
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* This is called on a life CPU, when a CPU is dead. So we cannot
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* access the hardware device itself.
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* We just set the mode and remove it from the lists.
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*/
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void tick_shutdown(unsigned int cpu)
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{
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struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
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struct clock_event_device *dev = td->evtdev;
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td->mode = TICKDEV_MODE_PERIODIC;
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if (dev) {
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/*
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* Prevent that the clock events layer tries to call
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* the set mode function!
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*/
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clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
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clockevents_exchange_device(dev, NULL);
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dev->event_handler = clockevents_handle_noop;
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td->evtdev = NULL;
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}
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}
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#endif
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/**
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* tick_suspend_local - Suspend the local tick device
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*
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* Called from the local cpu for freeze with interrupts disabled.
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*
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* No locks required. Nothing can change the per cpu device.
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*/
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void tick_suspend_local(void)
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{
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struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
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clockevents_shutdown(td->evtdev);
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}
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/**
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* tick_resume_local - Resume the local tick device
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*
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* Called from the local CPU for unfreeze or XEN resume magic.
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*
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* No locks required. Nothing can change the per cpu device.
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*/
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void tick_resume_local(void)
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{
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struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
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bool broadcast = tick_resume_check_broadcast();
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clockevents_tick_resume(td->evtdev);
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if (!broadcast) {
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if (td->mode == TICKDEV_MODE_PERIODIC)
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tick_setup_periodic(td->evtdev, 0);
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else
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tick_resume_oneshot();
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}
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}
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/**
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* tick_suspend - Suspend the tick and the broadcast device
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*
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* Called from syscore_suspend() via timekeeping_suspend with only one
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* CPU online and interrupts disabled or from tick_unfreeze() under
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* tick_freeze_lock.
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*
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* No locks required. Nothing can change the per cpu device.
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*/
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void tick_suspend(void)
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{
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tick_suspend_local();
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tick_suspend_broadcast();
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}
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/**
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* tick_resume - Resume the tick and the broadcast device
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*
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* Called from syscore_resume() via timekeeping_resume with only one
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* CPU online and interrupts disabled.
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*
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* No locks required. Nothing can change the per cpu device.
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*/
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void tick_resume(void)
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{
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tick_resume_broadcast();
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tick_resume_local();
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}
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#ifdef CONFIG_SUSPEND
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static DEFINE_RAW_SPINLOCK(tick_freeze_lock);
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static unsigned int tick_freeze_depth;
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/**
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* tick_freeze - Suspend the local tick and (possibly) timekeeping.
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*
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* Check if this is the last online CPU executing the function and if so,
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* suspend timekeeping. Otherwise suspend the local tick.
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*
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* Call with interrupts disabled. Must be balanced with %tick_unfreeze().
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* Interrupts must not be enabled before the subsequent %tick_unfreeze().
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*/
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void tick_freeze(void)
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{
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raw_spin_lock(&tick_freeze_lock);
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tick_freeze_depth++;
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if (tick_freeze_depth == num_online_cpus()) {
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trace_suspend_resume(TPS("timekeeping_freeze"),
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smp_processor_id(), true);
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system_state = SYSTEM_SUSPEND;
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sched_clock_suspend();
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timekeeping_suspend();
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} else {
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tick_suspend_local();
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}
|
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raw_spin_unlock(&tick_freeze_lock);
|
}
|
|
/**
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* tick_unfreeze - Resume the local tick and (possibly) timekeeping.
|
*
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* Check if this is the first CPU executing the function and if so, resume
|
* timekeeping. Otherwise resume the local tick.
|
*
|
* Call with interrupts disabled. Must be balanced with %tick_freeze().
|
* Interrupts must not be enabled after the preceding %tick_freeze().
|
*/
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void tick_unfreeze(void)
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{
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raw_spin_lock(&tick_freeze_lock);
|
|
if (tick_freeze_depth == num_online_cpus()) {
|
timekeeping_resume();
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sched_clock_resume();
|
system_state = SYSTEM_RUNNING;
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trace_suspend_resume(TPS("timekeeping_freeze"),
|
smp_processor_id(), false);
|
} else {
|
touch_softlockup_watchdog();
|
tick_resume_local();
|
}
|
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tick_freeze_depth--;
|
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raw_spin_unlock(&tick_freeze_lock);
|
}
|
#endif /* CONFIG_SUSPEND */
|
|
/**
|
* tick_init - initialize the tick control
|
*/
|
void __init tick_init(void)
|
{
|
tick_broadcast_init();
|
tick_nohz_init();
|
}
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