LCOV - code coverage report
Current view: top level - kernel/time - tick-common.c (source / functions) Hit Total Coverage
Test: coverage.info Lines: 55 127 43.3 %
Date: 2023-03-27 20:00:47 Functions: 9 19 47.4 %

          Line data    Source code
       1             : // SPDX-License-Identifier: GPL-2.0
       2             : /*
       3             :  * This file contains the base functions to manage periodic tick
       4             :  * related events.
       5             :  *
       6             :  * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
       7             :  * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
       8             :  * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
       9             :  */
      10             : #include <linux/cpu.h>
      11             : #include <linux/err.h>
      12             : #include <linux/hrtimer.h>
      13             : #include <linux/interrupt.h>
      14             : #include <linux/nmi.h>
      15             : #include <linux/percpu.h>
      16             : #include <linux/profile.h>
      17             : #include <linux/sched.h>
      18             : #include <linux/module.h>
      19             : #include <trace/events/power.h>
      20             : 
      21             : #include <asm/irq_regs.h>
      22             : 
      23             : #include "tick-internal.h"
      24             : 
      25             : /*
      26             :  * Tick devices
      27             :  */
      28             : DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
      29             : /*
      30             :  * Tick next event: keeps track of the tick time. It's updated by the
      31             :  * CPU which handles the tick and protected by jiffies_lock. There is
      32             :  * no requirement to write hold the jiffies seqcount for it.
      33             :  */
      34             : ktime_t tick_next_period;
      35             : 
      36             : /*
      37             :  * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR
      38             :  * which is responsible for calling do_timer(), i.e. the timekeeping stuff. This
      39             :  * variable has two functions:
      40             :  *
      41             :  * 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the
      42             :  *    timekeeping lock all at once. Only the CPU which is assigned to do the
      43             :  *    update is handling it.
      44             :  *
      45             :  * 2) Hand off the duty in the NOHZ idle case by setting the value to
      46             :  *    TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks
      47             :  *    at it will take over and keep the time keeping alive.  The handover
      48             :  *    procedure also covers cpu hotplug.
      49             :  */
      50             : int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
      51             : #ifdef CONFIG_NO_HZ_FULL
      52             : /*
      53             :  * tick_do_timer_boot_cpu indicates the boot CPU temporarily owns
      54             :  * tick_do_timer_cpu and it should be taken over by an eligible secondary
      55             :  * when one comes online.
      56             :  */
      57             : static int tick_do_timer_boot_cpu __read_mostly = -1;
      58             : #endif
      59             : 
      60             : /*
      61             :  * Debugging: see timer_list.c
      62             :  */
      63           0 : struct tick_device *tick_get_device(int cpu)
      64             : {
      65           0 :         return &per_cpu(tick_cpu_device, cpu);
      66             : }
      67             : 
      68             : /**
      69             :  * tick_is_oneshot_available - check for a oneshot capable event device
      70             :  */
      71           0 : int tick_is_oneshot_available(void)
      72             : {
      73           0 :         struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
      74             : 
      75           0 :         if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
      76             :                 return 0;
      77           0 :         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
      78             :                 return 1;
      79           0 :         return tick_broadcast_oneshot_available();
      80             : }
      81             : 
      82             : /*
      83             :  * Periodic tick
      84             :  */
      85        2723 : static void tick_periodic(int cpu)
      86             : {
      87        2723 :         if (tick_do_timer_cpu == cpu) {
      88        2723 :                 raw_spin_lock(&jiffies_lock);
      89        5446 :                 write_seqcount_begin(&jiffies_seq);
      90             : 
      91             :                 /* Keep track of the next tick event */
      92        2723 :                 tick_next_period = ktime_add_ns(tick_next_period, TICK_NSEC);
      93             : 
      94        2723 :                 do_timer(1);
      95        5446 :                 write_seqcount_end(&jiffies_seq);
      96        2723 :                 raw_spin_unlock(&jiffies_lock);
      97        2723 :                 update_wall_time();
      98             :         }
      99             : 
     100        2723 :         update_process_times(user_mode(get_irq_regs()));
     101        2723 :         profile_tick(CPU_PROFILING);
     102        2723 : }
     103             : 
     104             : /*
     105             :  * Event handler for periodic ticks
     106             :  */
     107        2723 : void tick_handle_periodic(struct clock_event_device *dev)
     108             : {
     109        2723 :         int cpu = smp_processor_id();
     110        2723 :         ktime_t next = dev->next_event;
     111             : 
     112        2723 :         tick_periodic(cpu);
     113             : 
     114             : #if defined(CONFIG_HIGH_RES_TIMERS) || defined(CONFIG_NO_HZ_COMMON)
     115             :         /*
     116             :          * The cpu might have transitioned to HIGHRES or NOHZ mode via
     117             :          * update_process_times() -> run_local_timers() ->
     118             :          * hrtimer_run_queues().
     119             :          */
     120             :         if (dev->event_handler != tick_handle_periodic)
     121             :                 return;
     122             : #endif
     123             : 
     124        2723 :         if (!clockevent_state_oneshot(dev))
     125             :                 return;
     126             :         for (;;) {
     127             :                 /*
     128             :                  * Setup the next period for devices, which do not have
     129             :                  * periodic mode:
     130             :                  */
     131           0 :                 next = ktime_add_ns(next, TICK_NSEC);
     132             : 
     133           0 :                 if (!clockevents_program_event(dev, next, false))
     134             :                         return;
     135             :                 /*
     136             :                  * Have to be careful here. If we're in oneshot mode,
     137             :                  * before we call tick_periodic() in a loop, we need
     138             :                  * to be sure we're using a real hardware clocksource.
     139             :                  * Otherwise we could get trapped in an infinite
     140             :                  * loop, as the tick_periodic() increments jiffies,
     141             :                  * which then will increment time, possibly causing
     142             :                  * the loop to trigger again and again.
     143             :                  */
     144           0 :                 if (timekeeping_valid_for_hres())
     145           0 :                         tick_periodic(cpu);
     146             :         }
     147             : }
     148             : 
     149             : /*
     150             :  * Setup the device for a periodic tick
     151             :  */
     152           1 : void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
     153             : {
     154           1 :         tick_set_periodic_handler(dev, broadcast);
     155             : 
     156             :         /* Broadcast setup ? */
     157           2 :         if (!tick_device_is_functional(dev))
     158             :                 return;
     159             : 
     160           1 :         if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
     161             :             !tick_broadcast_oneshot_active()) {
     162           1 :                 clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
     163             :         } else {
     164             :                 unsigned int seq;
     165             :                 ktime_t next;
     166             : 
     167             :                 do {
     168           0 :                         seq = read_seqcount_begin(&jiffies_seq);
     169           0 :                         next = tick_next_period;
     170           0 :                 } while (read_seqcount_retry(&jiffies_seq, seq));
     171             : 
     172           0 :                 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
     173             : 
     174             :                 for (;;) {
     175           0 :                         if (!clockevents_program_event(dev, next, false))
     176             :                                 return;
     177           0 :                         next = ktime_add_ns(next, TICK_NSEC);
     178             :                 }
     179             :         }
     180             : }
     181             : 
     182             : #ifdef CONFIG_NO_HZ_FULL
     183             : static void giveup_do_timer(void *info)
     184             : {
     185             :         int cpu = *(unsigned int *)info;
     186             : 
     187             :         WARN_ON(tick_do_timer_cpu != smp_processor_id());
     188             : 
     189             :         tick_do_timer_cpu = cpu;
     190             : }
     191             : 
     192             : static void tick_take_do_timer_from_boot(void)
     193             : {
     194             :         int cpu = smp_processor_id();
     195             :         int from = tick_do_timer_boot_cpu;
     196             : 
     197             :         if (from >= 0 && from != cpu)
     198             :                 smp_call_function_single(from, giveup_do_timer, &cpu, 1);
     199             : }
     200             : #endif
     201             : 
     202             : /*
     203             :  * Setup the tick device
     204             :  */
     205           1 : static void tick_setup_device(struct tick_device *td,
     206             :                               struct clock_event_device *newdev, int cpu,
     207             :                               const struct cpumask *cpumask)
     208             : {
     209           1 :         void (*handler)(struct clock_event_device *) = NULL;
     210           1 :         ktime_t next_event = 0;
     211             : 
     212             :         /*
     213             :          * First device setup ?
     214             :          */
     215           1 :         if (!td->evtdev) {
     216             :                 /*
     217             :                  * If no cpu took the do_timer update, assign it to
     218             :                  * this cpu:
     219             :                  */
     220           1 :                 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
     221           1 :                         tick_do_timer_cpu = cpu;
     222             : 
     223           1 :                         tick_next_period = ktime_get();
     224             : #ifdef CONFIG_NO_HZ_FULL
     225             :                         /*
     226             :                          * The boot CPU may be nohz_full, in which case set
     227             :                          * tick_do_timer_boot_cpu so the first housekeeping
     228             :                          * secondary that comes up will take do_timer from
     229             :                          * us.
     230             :                          */
     231             :                         if (tick_nohz_full_cpu(cpu))
     232             :                                 tick_do_timer_boot_cpu = cpu;
     233             : 
     234             :                 } else if (tick_do_timer_boot_cpu != -1 &&
     235             :                                                 !tick_nohz_full_cpu(cpu)) {
     236             :                         tick_take_do_timer_from_boot();
     237             :                         tick_do_timer_boot_cpu = -1;
     238             :                         WARN_ON(tick_do_timer_cpu != cpu);
     239             : #endif
     240             :                 }
     241             : 
     242             :                 /*
     243             :                  * Startup in periodic mode first.
     244             :                  */
     245           1 :                 td->mode = TICKDEV_MODE_PERIODIC;
     246             :         } else {
     247           0 :                 handler = td->evtdev->event_handler;
     248           0 :                 next_event = td->evtdev->next_event;
     249           0 :                 td->evtdev->event_handler = clockevents_handle_noop;
     250             :         }
     251             : 
     252           1 :         td->evtdev = newdev;
     253             : 
     254             :         /*
     255             :          * When the device is not per cpu, pin the interrupt to the
     256             :          * current cpu:
     257             :          */
     258           2 :         if (!cpumask_equal(newdev->cpumask, cpumask))
     259             :                 irq_set_affinity(newdev->irq, cpumask);
     260             : 
     261             :         /*
     262             :          * When global broadcasting is active, check if the current
     263             :          * device is registered as a placeholder for broadcast mode.
     264             :          * This allows us to handle this x86 misfeature in a generic
     265             :          * way. This function also returns !=0 when we keep the
     266             :          * current active broadcast state for this CPU.
     267             :          */
     268           1 :         if (tick_device_uses_broadcast(newdev, cpu))
     269             :                 return;
     270             : 
     271           1 :         if (td->mode == TICKDEV_MODE_PERIODIC)
     272           1 :                 tick_setup_periodic(newdev, 0);
     273             :         else
     274           0 :                 tick_setup_oneshot(newdev, handler, next_event);
     275             : }
     276             : 
     277           0 : void tick_install_replacement(struct clock_event_device *newdev)
     278             : {
     279           0 :         struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
     280           0 :         int cpu = smp_processor_id();
     281             : 
     282           0 :         clockevents_exchange_device(td->evtdev, newdev);
     283           0 :         tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
     284             :         if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
     285             :                 tick_oneshot_notify();
     286           0 : }
     287             : 
     288           1 : static bool tick_check_percpu(struct clock_event_device *curdev,
     289             :                               struct clock_event_device *newdev, int cpu)
     290             : {
     291           2 :         if (!cpumask_test_cpu(cpu, newdev->cpumask))
     292             :                 return false;
     293           3 :         if (cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
     294             :                 return true;
     295             :         /* Check if irq affinity can be set */
     296           0 :         if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq))
     297             :                 return false;
     298             :         /* Prefer an existing cpu local device */
     299           0 :         if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
     300             :                 return false;
     301             :         return true;
     302             : }
     303             : 
     304           1 : static bool tick_check_preferred(struct clock_event_device *curdev,
     305             :                                  struct clock_event_device *newdev)
     306             : {
     307             :         /* Prefer oneshot capable device */
     308           1 :         if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) {
     309           0 :                 if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT))
     310             :                         return false;
     311             :                 if (tick_oneshot_mode_active())
     312             :                         return false;
     313             :         }
     314             : 
     315             :         /*
     316             :          * Use the higher rated one, but prefer a CPU local device with a lower
     317             :          * rating than a non-CPU local device
     318             :          */
     319           0 :         return !curdev ||
     320           1 :                 newdev->rating > curdev->rating ||
     321           0 :                !cpumask_equal(curdev->cpumask, newdev->cpumask);
     322             : }
     323             : 
     324             : /*
     325             :  * Check whether the new device is a better fit than curdev. curdev
     326             :  * can be NULL !
     327             :  */
     328           1 : bool tick_check_replacement(struct clock_event_device *curdev,
     329             :                             struct clock_event_device *newdev)
     330             : {
     331           1 :         if (!tick_check_percpu(curdev, newdev, smp_processor_id()))
     332             :                 return false;
     333             : 
     334           1 :         return tick_check_preferred(curdev, newdev);
     335             : }
     336             : 
     337             : /*
     338             :  * Check, if the new registered device should be used. Called with
     339             :  * clockevents_lock held and interrupts disabled.
     340             :  */
     341           1 : void tick_check_new_device(struct clock_event_device *newdev)
     342             : {
     343             :         struct clock_event_device *curdev;
     344             :         struct tick_device *td;
     345             :         int cpu;
     346             : 
     347           1 :         cpu = smp_processor_id();
     348           1 :         td = &per_cpu(tick_cpu_device, cpu);
     349           1 :         curdev = td->evtdev;
     350             : 
     351           1 :         if (!tick_check_replacement(curdev, newdev))
     352             :                 goto out_bc;
     353             : 
     354           1 :         if (!try_module_get(newdev->owner))
     355             :                 return;
     356             : 
     357             :         /*
     358             :          * Replace the eventually existing device by the new
     359             :          * device. If the current device is the broadcast device, do
     360             :          * not give it back to the clockevents layer !
     361             :          */
     362           1 :         if (tick_is_broadcast_device(curdev)) {
     363             :                 clockevents_shutdown(curdev);
     364             :                 curdev = NULL;
     365             :         }
     366           1 :         clockevents_exchange_device(curdev, newdev);
     367           2 :         tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
     368             :         if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
     369             :                 tick_oneshot_notify();
     370             :         return;
     371             : 
     372             : out_bc:
     373             :         /*
     374             :          * Can the new device be used as a broadcast device ?
     375             :          */
     376             :         tick_install_broadcast_device(newdev, cpu);
     377             : }
     378             : 
     379             : /**
     380             :  * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
     381             :  * @state:      The target state (enter/exit)
     382             :  *
     383             :  * The system enters/leaves a state, where affected devices might stop
     384             :  * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
     385             :  *
     386             :  * Called with interrupts disabled, so clockevents_lock is not
     387             :  * required here because the local clock event device cannot go away
     388             :  * under us.
     389             :  */
     390           0 : int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
     391             : {
     392           0 :         struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
     393             : 
     394           0 :         if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))
     395             :                 return 0;
     396             : 
     397           0 :         return __tick_broadcast_oneshot_control(state);
     398             : }
     399             : EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control);
     400             : 
     401             : #ifdef CONFIG_HOTPLUG_CPU
     402             : /*
     403             :  * Transfer the do_timer job away from a dying cpu.
     404             :  *
     405             :  * Called with interrupts disabled. No locking required. If
     406             :  * tick_do_timer_cpu is owned by this cpu, nothing can change it.
     407             :  */
     408             : void tick_handover_do_timer(void)
     409             : {
     410             :         if (tick_do_timer_cpu == smp_processor_id())
     411             :                 tick_do_timer_cpu = cpumask_first(cpu_online_mask);
     412             : }
     413             : 
     414             : /*
     415             :  * Shutdown an event device on a given cpu:
     416             :  *
     417             :  * This is called on a life CPU, when a CPU is dead. So we cannot
     418             :  * access the hardware device itself.
     419             :  * We just set the mode and remove it from the lists.
     420             :  */
     421             : void tick_shutdown(unsigned int cpu)
     422             : {
     423             :         struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
     424             :         struct clock_event_device *dev = td->evtdev;
     425             : 
     426             :         td->mode = TICKDEV_MODE_PERIODIC;
     427             :         if (dev) {
     428             :                 /*
     429             :                  * Prevent that the clock events layer tries to call
     430             :                  * the set mode function!
     431             :                  */
     432             :                 clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
     433             :                 clockevents_exchange_device(dev, NULL);
     434             :                 dev->event_handler = clockevents_handle_noop;
     435             :                 td->evtdev = NULL;
     436             :         }
     437             : }
     438             : #endif
     439             : 
     440             : /**
     441             :  * tick_suspend_local - Suspend the local tick device
     442             :  *
     443             :  * Called from the local cpu for freeze with interrupts disabled.
     444             :  *
     445             :  * No locks required. Nothing can change the per cpu device.
     446             :  */
     447           0 : void tick_suspend_local(void)
     448             : {
     449           0 :         struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
     450             : 
     451           0 :         clockevents_shutdown(td->evtdev);
     452           0 : }
     453             : 
     454             : /**
     455             :  * tick_resume_local - Resume the local tick device
     456             :  *
     457             :  * Called from the local CPU for unfreeze or XEN resume magic.
     458             :  *
     459             :  * No locks required. Nothing can change the per cpu device.
     460             :  */
     461           0 : void tick_resume_local(void)
     462             : {
     463           0 :         struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
     464           0 :         bool broadcast = tick_resume_check_broadcast();
     465             : 
     466           0 :         clockevents_tick_resume(td->evtdev);
     467             :         if (!broadcast) {
     468           0 :                 if (td->mode == TICKDEV_MODE_PERIODIC)
     469           0 :                         tick_setup_periodic(td->evtdev, 0);
     470             :                 else
     471           0 :                         tick_resume_oneshot();
     472             :         }
     473             : 
     474             :         /*
     475             :          * Ensure that hrtimers are up to date and the clockevents device
     476             :          * is reprogrammed correctly when high resolution timers are
     477             :          * enabled.
     478             :          */
     479           0 :         hrtimers_resume_local();
     480           0 : }
     481             : 
     482             : /**
     483             :  * tick_suspend - Suspend the tick and the broadcast device
     484             :  *
     485             :  * Called from syscore_suspend() via timekeeping_suspend with only one
     486             :  * CPU online and interrupts disabled or from tick_unfreeze() under
     487             :  * tick_freeze_lock.
     488             :  *
     489             :  * No locks required. Nothing can change the per cpu device.
     490             :  */
     491           0 : void tick_suspend(void)
     492             : {
     493             :         tick_suspend_local();
     494             :         tick_suspend_broadcast();
     495           0 : }
     496             : 
     497             : /**
     498             :  * tick_resume - Resume the tick and the broadcast device
     499             :  *
     500             :  * Called from syscore_resume() via timekeeping_resume with only one
     501             :  * CPU online and interrupts disabled.
     502             :  *
     503             :  * No locks required. Nothing can change the per cpu device.
     504             :  */
     505           0 : void tick_resume(void)
     506             : {
     507             :         tick_resume_broadcast();
     508           0 :         tick_resume_local();
     509           0 : }
     510             : 
     511             : #ifdef CONFIG_SUSPEND
     512             : static DEFINE_RAW_SPINLOCK(tick_freeze_lock);
     513             : static unsigned int tick_freeze_depth;
     514             : 
     515             : /**
     516             :  * tick_freeze - Suspend the local tick and (possibly) timekeeping.
     517             :  *
     518             :  * Check if this is the last online CPU executing the function and if so,
     519             :  * suspend timekeeping.  Otherwise suspend the local tick.
     520             :  *
     521             :  * Call with interrupts disabled.  Must be balanced with %tick_unfreeze().
     522             :  * Interrupts must not be enabled before the subsequent %tick_unfreeze().
     523             :  */
     524           0 : void tick_freeze(void)
     525             : {
     526           0 :         raw_spin_lock(&tick_freeze_lock);
     527             : 
     528           0 :         tick_freeze_depth++;
     529           0 :         if (tick_freeze_depth == num_online_cpus()) {
     530           0 :                 trace_suspend_resume(TPS("timekeeping_freeze"),
     531             :                                      smp_processor_id(), true);
     532           0 :                 system_state = SYSTEM_SUSPEND;
     533             :                 sched_clock_suspend();
     534           0 :                 timekeeping_suspend();
     535             :         } else {
     536             :                 tick_suspend_local();
     537             :         }
     538             : 
     539           0 :         raw_spin_unlock(&tick_freeze_lock);
     540           0 : }
     541             : 
     542             : /**
     543             :  * tick_unfreeze - Resume the local tick and (possibly) timekeeping.
     544             :  *
     545             :  * Check if this is the first CPU executing the function and if so, resume
     546             :  * timekeeping.  Otherwise resume the local tick.
     547             :  *
     548             :  * Call with interrupts disabled.  Must be balanced with %tick_freeze().
     549             :  * Interrupts must not be enabled after the preceding %tick_freeze().
     550             :  */
     551           0 : void tick_unfreeze(void)
     552             : {
     553           0 :         raw_spin_lock(&tick_freeze_lock);
     554             : 
     555           0 :         if (tick_freeze_depth == num_online_cpus()) {
     556           0 :                 timekeeping_resume();
     557             :                 sched_clock_resume();
     558           0 :                 system_state = SYSTEM_RUNNING;
     559             :                 trace_suspend_resume(TPS("timekeeping_freeze"),
     560             :                                      smp_processor_id(), false);
     561             :         } else {
     562             :                 touch_softlockup_watchdog();
     563           0 :                 tick_resume_local();
     564             :         }
     565             : 
     566           0 :         tick_freeze_depth--;
     567             : 
     568           0 :         raw_spin_unlock(&tick_freeze_lock);
     569           0 : }
     570             : #endif /* CONFIG_SUSPEND */
     571             : 
     572             : /**
     573             :  * tick_init - initialize the tick control
     574             :  */
     575           1 : void __init tick_init(void)
     576             : {
     577             :         tick_broadcast_init();
     578             :         tick_nohz_init();
     579           1 : }

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