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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 */
28DEFINE_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 */
34ktime_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 */
50int 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 */
57static int tick_do_timer_boot_cpu __read_mostly = -1;
58#endif
59
60/*
61 * Debugging: see timer_list.c
62 */
63struct tick_device *tick_get_device(int cpu)
64{
65 return &per_cpu(tick_cpu_device, cpu);
66}
67
68/**
69 * tick_is_oneshot_available - check for a oneshot capable event device
70 */
71int tick_is_oneshot_available(void)
72{
73 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
74
75 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
76 return 0;
77 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
78 return 1;
79 return tick_broadcast_oneshot_available();
80}
81
82/*
83 * Periodic tick
84 */
85static void tick_periodic(int cpu)
86{
87 if (tick_do_timer_cpu == cpu) {
88 raw_spin_lock(&jiffies_lock);
89 write_seqcount_begin(&jiffies_seq);
90
91 /* Keep track of the next tick event */
92 tick_next_period = ktime_add_ns(tick_next_period, TICK_NSEC);
93
94 do_timer(1);
95 write_seqcount_end(&jiffies_seq);
96 raw_spin_unlock(&jiffies_lock);
97 update_wall_time();
98 }
99
100 update_process_times(user_mode(get_irq_regs()));
101 profile_tick(CPU_PROFILING);
102}
103
104/*
105 * Event handler for periodic ticks
106 */
107void tick_handle_periodic(struct clock_event_device *dev)
108{
109 int cpu = smp_processor_id();
110 ktime_t next = dev->next_event;
111
112 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 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 next = ktime_add_ns(next, TICK_NSEC);
132
133 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 if (timekeeping_valid_for_hres())
145 tick_periodic(cpu);
146 }
147}
148
149/*
150 * Setup the device for a periodic tick
151 */
152void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
153{
154 tick_set_periodic_handler(dev, broadcast);
155
156 /* Broadcast setup ? */
157 if (!tick_device_is_functional(dev))
158 return;
159
160 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
161 !tick_broadcast_oneshot_active()) {
162 clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
163 } else {
164 unsigned int seq;
165 ktime_t next;
166
167 do {
168 seq = read_seqcount_begin(&jiffies_seq);
169 next = tick_next_period;
170 } while (read_seqcount_retry(&jiffies_seq, seq));
171
172 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
173
174 for (;;) {
175 if (!clockevents_program_event(dev, next, false))
176 return;
177 next = ktime_add_ns(next, TICK_NSEC);
178 }
179 }
180}
181
182#ifdef CONFIG_NO_HZ_FULL
183static 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
192static 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 */
205static void tick_setup_device(struct tick_device *td,
206 struct clock_event_device *newdev, int cpu,
207 const struct cpumask *cpumask)
208{
209 void (*handler)(struct clock_event_device *) = NULL;
210 ktime_t next_event = 0;
211
212 /*
213 * First device setup ?
214 */
215 if (!td->evtdev) {
216 /*
217 * If no cpu took the do_timer update, assign it to
218 * this cpu:
219 */
220 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
221 tick_do_timer_cpu = cpu;
222 tick_next_period = ktime_get();
223#ifdef CONFIG_NO_HZ_FULL
224 /*
225 * The boot CPU may be nohz_full, in which case set
226 * tick_do_timer_boot_cpu so the first housekeeping
227 * secondary that comes up will take do_timer from
228 * us.
229 */
230 if (tick_nohz_full_cpu(cpu))
231 tick_do_timer_boot_cpu = cpu;
232
233 } else if (tick_do_timer_boot_cpu != -1 &&
234 !tick_nohz_full_cpu(cpu)) {
235 tick_take_do_timer_from_boot();
236 tick_do_timer_boot_cpu = -1;
237 WARN_ON(tick_do_timer_cpu != cpu);
238#endif
239 }
240
241 /*
242 * Startup in periodic mode first.
243 */
244 td->mode = TICKDEV_MODE_PERIODIC;
245 } else {
246 handler = td->evtdev->event_handler;
247 next_event = td->evtdev->next_event;
248 td->evtdev->event_handler = clockevents_handle_noop;
249 }
250
251 td->evtdev = newdev;
252
253 /*
254 * When the device is not per cpu, pin the interrupt to the
255 * current cpu:
256 */
257 if (!cpumask_equal(newdev->cpumask, cpumask))
258 irq_set_affinity(newdev->irq, cpumask);
259
260 /*
261 * When global broadcasting is active, check if the current
262 * device is registered as a placeholder for broadcast mode.
263 * This allows us to handle this x86 misfeature in a generic
264 * way. This function also returns !=0 when we keep the
265 * current active broadcast state for this CPU.
266 */
267 if (tick_device_uses_broadcast(newdev, cpu))
268 return;
269
270 if (td->mode == TICKDEV_MODE_PERIODIC)
271 tick_setup_periodic(newdev, 0);
272 else
273 tick_setup_oneshot(newdev, handler, next_event);
274}
275
276void tick_install_replacement(struct clock_event_device *newdev)
277{
278 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
279 int cpu = smp_processor_id();
280
281 clockevents_exchange_device(td->evtdev, newdev);
282 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
283 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
284 tick_oneshot_notify();
285}
286
287static bool tick_check_percpu(struct clock_event_device *curdev,
288 struct clock_event_device *newdev, int cpu)
289{
290 if (!cpumask_test_cpu(cpu, newdev->cpumask))
291 return false;
292 if (cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
293 return true;
294 /* Check if irq affinity can be set */
295 if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq))
296 return false;
297 /* Prefer an existing cpu local device */
298 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
299 return false;
300 return true;
301}
302
303static bool tick_check_preferred(struct clock_event_device *curdev,
304 struct clock_event_device *newdev)
305{
306 /* Prefer oneshot capable device */
307 if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) {
308 if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT))
309 return false;
310 if (tick_oneshot_mode_active())
311 return false;
312 }
313
314 /*
315 * Use the higher rated one, but prefer a CPU local device with a lower
316 * rating than a non-CPU local device
317 */
318 return !curdev ||
319 newdev->rating > curdev->rating ||
320 !cpumask_equal(curdev->cpumask, newdev->cpumask);
321}
322
323/*
324 * Check whether the new device is a better fit than curdev. curdev
325 * can be NULL !
326 */
327bool tick_check_replacement(struct clock_event_device *curdev,
328 struct clock_event_device *newdev)
329{
330 if (!tick_check_percpu(curdev, newdev, smp_processor_id()))
331 return false;
332
333 return tick_check_preferred(curdev, newdev);
334}
335
336/*
337 * Check, if the new registered device should be used. Called with
338 * clockevents_lock held and interrupts disabled.
339 */
340void tick_check_new_device(struct clock_event_device *newdev)
341{
342 struct clock_event_device *curdev;
343 struct tick_device *td;
344 int cpu;
345
346 cpu = smp_processor_id();
347 td = &per_cpu(tick_cpu_device, cpu);
348 curdev = td->evtdev;
349
350 if (!tick_check_replacement(curdev, newdev))
351 goto out_bc;
352
353 if (!try_module_get(newdev->owner))
354 return;
355
356 /*
357 * Replace the eventually existing device by the new
358 * device. If the current device is the broadcast device, do
359 * not give it back to the clockevents layer !
360 */
361 if (tick_is_broadcast_device(curdev)) {
362 clockevents_shutdown(curdev);
363 curdev = NULL;
364 }
365 clockevents_exchange_device(curdev, newdev);
366 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
367 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
368 tick_oneshot_notify();
369 return;
370
371out_bc:
372 /*
373 * Can the new device be used as a broadcast device ?
374 */
375 tick_install_broadcast_device(newdev, cpu);
376}
377
378/**
379 * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
380 * @state: The target state (enter/exit)
381 *
382 * The system enters/leaves a state, where affected devices might stop
383 * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
384 *
385 * Called with interrupts disabled, so clockevents_lock is not
386 * required here because the local clock event device cannot go away
387 * under us.
388 */
389int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
390{
391 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
392
393 if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))
394 return 0;
395
396 return __tick_broadcast_oneshot_control(state);
397}
398EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control);
399
400#ifdef CONFIG_HOTPLUG_CPU
401/*
402 * Transfer the do_timer job away from a dying cpu.
403 *
404 * Called with interrupts disabled. No locking required. If
405 * tick_do_timer_cpu is owned by this cpu, nothing can change it.
406 */
407void tick_handover_do_timer(void)
408{
409 if (tick_do_timer_cpu == smp_processor_id())
410 tick_do_timer_cpu = cpumask_first(cpu_online_mask);
411}
412
413/*
414 * Shutdown an event device on a given cpu:
415 *
416 * This is called on a life CPU, when a CPU is dead. So we cannot
417 * access the hardware device itself.
418 * We just set the mode and remove it from the lists.
419 */
420void tick_shutdown(unsigned int cpu)
421{
422 struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
423 struct clock_event_device *dev = td->evtdev;
424
425 td->mode = TICKDEV_MODE_PERIODIC;
426 if (dev) {
427 /*
428 * Prevent that the clock events layer tries to call
429 * the set mode function!
430 */
431 clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
432 clockevents_exchange_device(dev, NULL);
433 dev->event_handler = clockevents_handle_noop;
434 td->evtdev = NULL;
435 }
436}
437#endif
438
439/**
440 * tick_suspend_local - Suspend the local tick device
441 *
442 * Called from the local cpu for freeze with interrupts disabled.
443 *
444 * No locks required. Nothing can change the per cpu device.
445 */
446void tick_suspend_local(void)
447{
448 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
449
450 clockevents_shutdown(td->evtdev);
451}
452
453/**
454 * tick_resume_local - Resume the local tick device
455 *
456 * Called from the local CPU for unfreeze or XEN resume magic.
457 *
458 * No locks required. Nothing can change the per cpu device.
459 */
460void tick_resume_local(void)
461{
462 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
463 bool broadcast = tick_resume_check_broadcast();
464
465 clockevents_tick_resume(td->evtdev);
466 if (!broadcast) {
467 if (td->mode == TICKDEV_MODE_PERIODIC)
468 tick_setup_periodic(td->evtdev, 0);
469 else
470 tick_resume_oneshot();
471 }
472
473 /*
474 * Ensure that hrtimers are up to date and the clockevents device
475 * is reprogrammed correctly when high resolution timers are
476 * enabled.
477 */
478 hrtimers_resume_local();
479}
480
481/**
482 * tick_suspend - Suspend the tick and the broadcast device
483 *
484 * Called from syscore_suspend() via timekeeping_suspend with only one
485 * CPU online and interrupts disabled or from tick_unfreeze() under
486 * tick_freeze_lock.
487 *
488 * No locks required. Nothing can change the per cpu device.
489 */
490void tick_suspend(void)
491{
492 tick_suspend_local();
493 tick_suspend_broadcast();
494}
495
496/**
497 * tick_resume - Resume the tick and the broadcast device
498 *
499 * Called from syscore_resume() via timekeeping_resume with only one
500 * CPU online and interrupts disabled.
501 *
502 * No locks required. Nothing can change the per cpu device.
503 */
504void tick_resume(void)
505{
506 tick_resume_broadcast();
507 tick_resume_local();
508}
509
510#ifdef CONFIG_SUSPEND
511static DEFINE_RAW_SPINLOCK(tick_freeze_lock);
512static unsigned int tick_freeze_depth;
513
514/**
515 * tick_freeze - Suspend the local tick and (possibly) timekeeping.
516 *
517 * Check if this is the last online CPU executing the function and if so,
518 * suspend timekeeping. Otherwise suspend the local tick.
519 *
520 * Call with interrupts disabled. Must be balanced with %tick_unfreeze().
521 * Interrupts must not be enabled before the subsequent %tick_unfreeze().
522 */
523void tick_freeze(void)
524{
525 raw_spin_lock(&tick_freeze_lock);
526
527 tick_freeze_depth++;
528 if (tick_freeze_depth == num_online_cpus()) {
529 trace_suspend_resume(TPS("timekeeping_freeze"),
530 smp_processor_id(), true);
531 system_state = SYSTEM_SUSPEND;
532 sched_clock_suspend();
533 timekeeping_suspend();
534 } else {
535 tick_suspend_local();
536 }
537
538 raw_spin_unlock(&tick_freeze_lock);
539}
540
541/**
542 * tick_unfreeze - Resume the local tick and (possibly) timekeeping.
543 *
544 * Check if this is the first CPU executing the function and if so, resume
545 * timekeeping. Otherwise resume the local tick.
546 *
547 * Call with interrupts disabled. Must be balanced with %tick_freeze().
548 * Interrupts must not be enabled after the preceding %tick_freeze().
549 */
550void tick_unfreeze(void)
551{
552 raw_spin_lock(&tick_freeze_lock);
553
554 if (tick_freeze_depth == num_online_cpus()) {
555 timekeeping_resume();
556 sched_clock_resume();
557 system_state = SYSTEM_RUNNING;
558 trace_suspend_resume(TPS("timekeeping_freeze"),
559 smp_processor_id(), false);
560 } else {
561 touch_softlockup_watchdog();
562 tick_resume_local();
563 }
564
565 tick_freeze_depth--;
566
567 raw_spin_unlock(&tick_freeze_lock);
568}
569#endif /* CONFIG_SUSPEND */
570
571/**
572 * tick_init - initialize the tick control
573 */
574void __init tick_init(void)
575{
576 tick_broadcast_init();
577 tick_nohz_init();
578}
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/compiler.h>
11#include <linux/cpu.h>
12#include <linux/err.h>
13#include <linux/hrtimer.h>
14#include <linux/interrupt.h>
15#include <linux/nmi.h>
16#include <linux/percpu.h>
17#include <linux/profile.h>
18#include <linux/sched.h>
19#include <linux/module.h>
20#include <trace/events/power.h>
21
22#include <asm/irq_regs.h>
23
24#include "tick-internal.h"
25
26/*
27 * Tick devices
28 */
29DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
30/*
31 * Tick next event: keeps track of the tick time. It's updated by the
32 * CPU which handles the tick and protected by jiffies_lock. There is
33 * no requirement to write hold the jiffies seqcount for it.
34 */
35ktime_t tick_next_period;
36
37/*
38 * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR
39 * which is responsible for calling do_timer(), i.e. the timekeeping stuff. This
40 * variable has two functions:
41 *
42 * 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the
43 * timekeeping lock all at once. Only the CPU which is assigned to do the
44 * update is handling it.
45 *
46 * 2) Hand off the duty in the NOHZ idle case by setting the value to
47 * TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks
48 * at it will take over and keep the time keeping alive. The handover
49 * procedure also covers cpu hotplug.
50 */
51int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
52#ifdef CONFIG_NO_HZ_FULL
53/*
54 * tick_do_timer_boot_cpu indicates the boot CPU temporarily owns
55 * tick_do_timer_cpu and it should be taken over by an eligible secondary
56 * when one comes online.
57 */
58static int tick_do_timer_boot_cpu __read_mostly = -1;
59#endif
60
61/*
62 * Debugging: see timer_list.c
63 */
64struct tick_device *tick_get_device(int cpu)
65{
66 return &per_cpu(tick_cpu_device, cpu);
67}
68
69/**
70 * tick_is_oneshot_available - check for a oneshot capable event device
71 */
72int tick_is_oneshot_available(void)
73{
74 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
75
76 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
77 return 0;
78 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
79 return 1;
80 return tick_broadcast_oneshot_available();
81}
82
83/*
84 * Periodic tick
85 */
86static void tick_periodic(int cpu)
87{
88 if (READ_ONCE(tick_do_timer_cpu) == cpu) {
89 raw_spin_lock(&jiffies_lock);
90 write_seqcount_begin(&jiffies_seq);
91
92 /* Keep track of the next tick event */
93 tick_next_period = ktime_add_ns(tick_next_period, TICK_NSEC);
94
95 do_timer(1);
96 write_seqcount_end(&jiffies_seq);
97 raw_spin_unlock(&jiffies_lock);
98 update_wall_time();
99 }
100
101 update_process_times(user_mode(get_irq_regs()));
102 profile_tick(CPU_PROFILING);
103}
104
105/*
106 * Event handler for periodic ticks
107 */
108void tick_handle_periodic(struct clock_event_device *dev)
109{
110 int cpu = smp_processor_id();
111 ktime_t next = dev->next_event;
112
113 tick_periodic(cpu);
114
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 (IS_ENABLED(CONFIG_TICK_ONESHOT) && dev->event_handler != tick_handle_periodic)
121 return;
122
123 if (!clockevent_state_oneshot(dev))
124 return;
125 for (;;) {
126 /*
127 * Setup the next period for devices, which do not have
128 * periodic mode:
129 */
130 next = ktime_add_ns(next, TICK_NSEC);
131
132 if (!clockevents_program_event(dev, next, false))
133 return;
134 /*
135 * Have to be careful here. If we're in oneshot mode,
136 * before we call tick_periodic() in a loop, we need
137 * to be sure we're using a real hardware clocksource.
138 * Otherwise we could get trapped in an infinite
139 * loop, as the tick_periodic() increments jiffies,
140 * which then will increment time, possibly causing
141 * the loop to trigger again and again.
142 */
143 if (timekeeping_valid_for_hres())
144 tick_periodic(cpu);
145 }
146}
147
148/*
149 * Setup the device for a periodic tick
150 */
151void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
152{
153 tick_set_periodic_handler(dev, broadcast);
154
155 /* Broadcast setup ? */
156 if (!tick_device_is_functional(dev))
157 return;
158
159 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
160 !tick_broadcast_oneshot_active()) {
161 clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
162 } else {
163 unsigned int seq;
164 ktime_t next;
165
166 do {
167 seq = read_seqcount_begin(&jiffies_seq);
168 next = tick_next_period;
169 } while (read_seqcount_retry(&jiffies_seq, seq));
170
171 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
172
173 for (;;) {
174 if (!clockevents_program_event(dev, next, false))
175 return;
176 next = ktime_add_ns(next, TICK_NSEC);
177 }
178 }
179}
180
181#ifdef CONFIG_NO_HZ_FULL
182static void giveup_do_timer(void *info)
183{
184 int cpu = *(unsigned int *)info;
185
186 WARN_ON(tick_do_timer_cpu != smp_processor_id());
187
188 tick_do_timer_cpu = cpu;
189}
190
191static void tick_take_do_timer_from_boot(void)
192{
193 int cpu = smp_processor_id();
194 int from = tick_do_timer_boot_cpu;
195
196 if (from >= 0 && from != cpu)
197 smp_call_function_single(from, giveup_do_timer, &cpu, 1);
198}
199#endif
200
201/*
202 * Setup the tick device
203 */
204static void tick_setup_device(struct tick_device *td,
205 struct clock_event_device *newdev, int cpu,
206 const struct cpumask *cpumask)
207{
208 void (*handler)(struct clock_event_device *) = NULL;
209 ktime_t next_event = 0;
210
211 /*
212 * First device setup ?
213 */
214 if (!td->evtdev) {
215 /*
216 * If no cpu took the do_timer update, assign it to
217 * this cpu:
218 */
219 if (READ_ONCE(tick_do_timer_cpu) == TICK_DO_TIMER_BOOT) {
220 WRITE_ONCE(tick_do_timer_cpu, cpu);
221 tick_next_period = ktime_get();
222#ifdef CONFIG_NO_HZ_FULL
223 /*
224 * The boot CPU may be nohz_full, in which case set
225 * tick_do_timer_boot_cpu so the first housekeeping
226 * secondary that comes up will take do_timer from
227 * us.
228 */
229 if (tick_nohz_full_cpu(cpu))
230 tick_do_timer_boot_cpu = cpu;
231
232 } else if (tick_do_timer_boot_cpu != -1 &&
233 !tick_nohz_full_cpu(cpu)) {
234 tick_take_do_timer_from_boot();
235 tick_do_timer_boot_cpu = -1;
236 WARN_ON(READ_ONCE(tick_do_timer_cpu) != cpu);
237#endif
238 }
239
240 /*
241 * Startup in periodic mode first.
242 */
243 td->mode = TICKDEV_MODE_PERIODIC;
244 } else {
245 handler = td->evtdev->event_handler;
246 next_event = td->evtdev->next_event;
247 td->evtdev->event_handler = clockevents_handle_noop;
248 }
249
250 td->evtdev = newdev;
251
252 /*
253 * When the device is not per cpu, pin the interrupt to the
254 * current cpu:
255 */
256 if (!cpumask_equal(newdev->cpumask, cpumask))
257 irq_set_affinity(newdev->irq, cpumask);
258
259 /*
260 * When global broadcasting is active, check if the current
261 * device is registered as a placeholder for broadcast mode.
262 * This allows us to handle this x86 misfeature in a generic
263 * way. This function also returns !=0 when we keep the
264 * current active broadcast state for this CPU.
265 */
266 if (tick_device_uses_broadcast(newdev, cpu))
267 return;
268
269 if (td->mode == TICKDEV_MODE_PERIODIC)
270 tick_setup_periodic(newdev, 0);
271 else
272 tick_setup_oneshot(newdev, handler, next_event);
273}
274
275void tick_install_replacement(struct clock_event_device *newdev)
276{
277 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
278 int cpu = smp_processor_id();
279
280 clockevents_exchange_device(td->evtdev, newdev);
281 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
282 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
283 tick_oneshot_notify();
284}
285
286static bool tick_check_percpu(struct clock_event_device *curdev,
287 struct clock_event_device *newdev, int cpu)
288{
289 if (!cpumask_test_cpu(cpu, newdev->cpumask))
290 return false;
291 if (cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
292 return true;
293 /* Check if irq affinity can be set */
294 if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq))
295 return false;
296 /* Prefer an existing cpu local device */
297 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
298 return false;
299 return true;
300}
301
302static bool tick_check_preferred(struct clock_event_device *curdev,
303 struct clock_event_device *newdev)
304{
305 /* Prefer oneshot capable device */
306 if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) {
307 if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT))
308 return false;
309 if (tick_oneshot_mode_active())
310 return false;
311 }
312
313 /*
314 * Use the higher rated one, but prefer a CPU local device with a lower
315 * rating than a non-CPU local device
316 */
317 return !curdev ||
318 newdev->rating > curdev->rating ||
319 !cpumask_equal(curdev->cpumask, newdev->cpumask);
320}
321
322/*
323 * Check whether the new device is a better fit than curdev. curdev
324 * can be NULL !
325 */
326bool tick_check_replacement(struct clock_event_device *curdev,
327 struct clock_event_device *newdev)
328{
329 if (!tick_check_percpu(curdev, newdev, smp_processor_id()))
330 return false;
331
332 return tick_check_preferred(curdev, newdev);
333}
334
335/*
336 * Check, if the new registered device should be used. Called with
337 * clockevents_lock held and interrupts disabled.
338 */
339void tick_check_new_device(struct clock_event_device *newdev)
340{
341 struct clock_event_device *curdev;
342 struct tick_device *td;
343 int cpu;
344
345 cpu = smp_processor_id();
346 td = &per_cpu(tick_cpu_device, cpu);
347 curdev = td->evtdev;
348
349 if (!tick_check_replacement(curdev, newdev))
350 goto out_bc;
351
352 if (!try_module_get(newdev->owner))
353 return;
354
355 /*
356 * Replace the eventually existing device by the new
357 * device. If the current device is the broadcast device, do
358 * not give it back to the clockevents layer !
359 */
360 if (tick_is_broadcast_device(curdev)) {
361 clockevents_shutdown(curdev);
362 curdev = NULL;
363 }
364 clockevents_exchange_device(curdev, newdev);
365 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
366 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
367 tick_oneshot_notify();
368 return;
369
370out_bc:
371 /*
372 * Can the new device be used as a broadcast device ?
373 */
374 tick_install_broadcast_device(newdev, cpu);
375}
376
377/**
378 * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
379 * @state: The target state (enter/exit)
380 *
381 * The system enters/leaves a state, where affected devices might stop
382 * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
383 *
384 * Called with interrupts disabled, so clockevents_lock is not
385 * required here because the local clock event device cannot go away
386 * under us.
387 */
388int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
389{
390 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
391
392 if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))
393 return 0;
394
395 return __tick_broadcast_oneshot_control(state);
396}
397EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control);
398
399#ifdef CONFIG_HOTPLUG_CPU
400void tick_assert_timekeeping_handover(void)
401{
402 WARN_ON_ONCE(tick_do_timer_cpu == smp_processor_id());
403}
404/*
405 * Stop the tick and transfer the timekeeping job away from a dying cpu.
406 */
407int tick_cpu_dying(unsigned int dying_cpu)
408{
409 /*
410 * If the current CPU is the timekeeper, it's the only one that can
411 * safely hand over its duty. Also all online CPUs are in stop
412 * machine, guaranteed not to be idle, therefore there is no
413 * concurrency and it's safe to pick any online successor.
414 */
415 if (tick_do_timer_cpu == dying_cpu)
416 tick_do_timer_cpu = cpumask_first(cpu_online_mask);
417
418 /* Make sure the CPU won't try to retake the timekeeping duty */
419 tick_sched_timer_dying(dying_cpu);
420
421 /* Remove CPU from timer broadcasting */
422 tick_offline_cpu(dying_cpu);
423
424 return 0;
425}
426
427/*
428 * Shutdown an event device on a given cpu:
429 *
430 * This is called on a life CPU, when a CPU is dead. So we cannot
431 * access the hardware device itself.
432 * We just set the mode and remove it from the lists.
433 */
434void tick_shutdown(unsigned int cpu)
435{
436 struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
437 struct clock_event_device *dev = td->evtdev;
438
439 td->mode = TICKDEV_MODE_PERIODIC;
440 if (dev) {
441 /*
442 * Prevent that the clock events layer tries to call
443 * the set mode function!
444 */
445 clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
446 clockevents_exchange_device(dev, NULL);
447 dev->event_handler = clockevents_handle_noop;
448 td->evtdev = NULL;
449 }
450}
451#endif
452
453/**
454 * tick_suspend_local - Suspend the local tick device
455 *
456 * Called from the local cpu for freeze with interrupts disabled.
457 *
458 * No locks required. Nothing can change the per cpu device.
459 */
460void tick_suspend_local(void)
461{
462 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
463
464 clockevents_shutdown(td->evtdev);
465}
466
467/**
468 * tick_resume_local - Resume the local tick device
469 *
470 * Called from the local CPU for unfreeze or XEN resume magic.
471 *
472 * No locks required. Nothing can change the per cpu device.
473 */
474void tick_resume_local(void)
475{
476 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
477 bool broadcast = tick_resume_check_broadcast();
478
479 clockevents_tick_resume(td->evtdev);
480 if (!broadcast) {
481 if (td->mode == TICKDEV_MODE_PERIODIC)
482 tick_setup_periodic(td->evtdev, 0);
483 else
484 tick_resume_oneshot();
485 }
486
487 /*
488 * Ensure that hrtimers are up to date and the clockevents device
489 * is reprogrammed correctly when high resolution timers are
490 * enabled.
491 */
492 hrtimers_resume_local();
493}
494
495/**
496 * tick_suspend - Suspend the tick and the broadcast device
497 *
498 * Called from syscore_suspend() via timekeeping_suspend with only one
499 * CPU online and interrupts disabled or from tick_unfreeze() under
500 * tick_freeze_lock.
501 *
502 * No locks required. Nothing can change the per cpu device.
503 */
504void tick_suspend(void)
505{
506 tick_suspend_local();
507 tick_suspend_broadcast();
508}
509
510/**
511 * tick_resume - Resume the tick and the broadcast device
512 *
513 * Called from syscore_resume() via timekeeping_resume with only one
514 * CPU online and interrupts disabled.
515 *
516 * No locks required. Nothing can change the per cpu device.
517 */
518void tick_resume(void)
519{
520 tick_resume_broadcast();
521 tick_resume_local();
522}
523
524#ifdef CONFIG_SUSPEND
525static DEFINE_RAW_SPINLOCK(tick_freeze_lock);
526static unsigned int tick_freeze_depth;
527
528/**
529 * tick_freeze - Suspend the local tick and (possibly) timekeeping.
530 *
531 * Check if this is the last online CPU executing the function and if so,
532 * suspend timekeeping. Otherwise suspend the local tick.
533 *
534 * Call with interrupts disabled. Must be balanced with %tick_unfreeze().
535 * Interrupts must not be enabled before the subsequent %tick_unfreeze().
536 */
537void tick_freeze(void)
538{
539 raw_spin_lock(&tick_freeze_lock);
540
541 tick_freeze_depth++;
542 if (tick_freeze_depth == num_online_cpus()) {
543 trace_suspend_resume(TPS("timekeeping_freeze"),
544 smp_processor_id(), true);
545 system_state = SYSTEM_SUSPEND;
546 sched_clock_suspend();
547 timekeeping_suspend();
548 } else {
549 tick_suspend_local();
550 }
551
552 raw_spin_unlock(&tick_freeze_lock);
553}
554
555/**
556 * tick_unfreeze - Resume the local tick and (possibly) timekeeping.
557 *
558 * Check if this is the first CPU executing the function and if so, resume
559 * timekeeping. Otherwise resume the local tick.
560 *
561 * Call with interrupts disabled. Must be balanced with %tick_freeze().
562 * Interrupts must not be enabled after the preceding %tick_freeze().
563 */
564void tick_unfreeze(void)
565{
566 raw_spin_lock(&tick_freeze_lock);
567
568 if (tick_freeze_depth == num_online_cpus()) {
569 timekeeping_resume();
570 sched_clock_resume();
571 system_state = SYSTEM_RUNNING;
572 trace_suspend_resume(TPS("timekeeping_freeze"),
573 smp_processor_id(), false);
574 } else {
575 touch_softlockup_watchdog();
576 tick_resume_local();
577 }
578
579 tick_freeze_depth--;
580
581 raw_spin_unlock(&tick_freeze_lock);
582}
583#endif /* CONFIG_SUSPEND */
584
585/**
586 * tick_init - initialize the tick control
587 */
588void __init tick_init(void)
589{
590 tick_broadcast_init();
591 tick_nohz_init();
592}