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