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Commit | Line | Data |
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906568c9 TG |
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> | |
d7b90689 | 17 | #include <linux/interrupt.h> |
906568c9 TG |
18 | #include <linux/percpu.h> |
19 | #include <linux/profile.h> | |
20 | #include <linux/sched.h> | |
ccf33d68 | 21 | #include <linux/module.h> |
906568c9 | 22 | |
d7b90689 RK |
23 | #include <asm/irq_regs.h> |
24 | ||
f8381cba TG |
25 | #include "tick-internal.h" |
26 | ||
906568c9 TG |
27 | /* |
28 | * Tick devices | |
29 | */ | |
f8381cba | 30 | DEFINE_PER_CPU(struct tick_device, tick_cpu_device); |
906568c9 TG |
31 | /* |
32 | * Tick next event: keeps track of the tick time | |
33 | */ | |
f8381cba TG |
34 | ktime_t tick_next_period; |
35 | ktime_t tick_period; | |
050ded1b AM |
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 | */ | |
6441402b | 51 | int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT; |
906568c9 | 52 | |
289f480a IM |
53 | /* |
54 | * Debugging: see timer_list.c | |
55 | */ | |
56 | struct tick_device *tick_get_device(int cpu) | |
57 | { | |
58 | return &per_cpu(tick_cpu_device, cpu); | |
59 | } | |
60 | ||
79bf2bb3 TG |
61 | /** |
62 | * tick_is_oneshot_available - check for a oneshot capable event device | |
63 | */ | |
64 | int tick_is_oneshot_available(void) | |
65 | { | |
909ea964 | 66 | struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); |
79bf2bb3 | 67 | |
3a142a06 TG |
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(); | |
79bf2bb3 TG |
73 | } |
74 | ||
906568c9 TG |
75 | /* |
76 | * Periodic tick | |
77 | */ | |
78 | static void tick_periodic(int cpu) | |
79 | { | |
80 | if (tick_do_timer_cpu == cpu) { | |
d6ad4187 | 81 | write_seqlock(&jiffies_lock); |
906568c9 TG |
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); | |
d6ad4187 | 87 | write_sequnlock(&jiffies_lock); |
47a1b796 | 88 | update_wall_time(); |
906568c9 TG |
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 | */ | |
98 | void tick_handle_periodic(struct clock_event_device *dev) | |
99 | { | |
100 | int cpu = smp_processor_id(); | |
b97f0291 | 101 | ktime_t next = dev->next_event; |
906568c9 TG |
102 | |
103 | tick_periodic(cpu); | |
104 | ||
c6eb3f70 TG |
105 | #if defined(CONFIG_HIGH_RES_TIMERS) || defined(CONFIG_NO_HZ_COMMON) |
106 | /* | |
107 | * The cpu might have transitioned to HIGHRES or NOHZ mode via | |
108 | * update_process_times() -> run_local_timers() -> | |
109 | * hrtimer_run_queues(). | |
110 | */ | |
111 | if (dev->event_handler != tick_handle_periodic) | |
112 | return; | |
113 | #endif | |
114 | ||
472c4a94 | 115 | if (!clockevent_state_oneshot(dev)) |
906568c9 | 116 | return; |
906568c9 | 117 | for (;;) { |
b97f0291 VK |
118 | /* |
119 | * Setup the next period for devices, which do not have | |
120 | * periodic mode: | |
121 | */ | |
122 | next = ktime_add(next, tick_period); | |
123 | ||
d1748302 | 124 | if (!clockevents_program_event(dev, next, false)) |
906568c9 | 125 | return; |
74a03b69 JS |
126 | /* |
127 | * Have to be careful here. If we're in oneshot mode, | |
128 | * before we call tick_periodic() in a loop, we need | |
129 | * to be sure we're using a real hardware clocksource. | |
130 | * Otherwise we could get trapped in an infinite | |
131 | * loop, as the tick_periodic() increments jiffies, | |
cacb3c76 | 132 | * which then will increment time, possibly causing |
74a03b69 JS |
133 | * the loop to trigger again and again. |
134 | */ | |
135 | if (timekeeping_valid_for_hres()) | |
136 | tick_periodic(cpu); | |
906568c9 TG |
137 | } |
138 | } | |
139 | ||
140 | /* | |
141 | * Setup the device for a periodic tick | |
142 | */ | |
f8381cba | 143 | void tick_setup_periodic(struct clock_event_device *dev, int broadcast) |
906568c9 | 144 | { |
f8381cba TG |
145 | tick_set_periodic_handler(dev, broadcast); |
146 | ||
147 | /* Broadcast setup ? */ | |
148 | if (!tick_device_is_functional(dev)) | |
149 | return; | |
906568c9 | 150 | |
27ce4cb4 TG |
151 | if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) && |
152 | !tick_broadcast_oneshot_active()) { | |
d7eb231c | 153 | clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC); |
906568c9 TG |
154 | } else { |
155 | unsigned long seq; | |
156 | ktime_t next; | |
157 | ||
158 | do { | |
d6ad4187 | 159 | seq = read_seqbegin(&jiffies_lock); |
906568c9 | 160 | next = tick_next_period; |
d6ad4187 | 161 | } while (read_seqretry(&jiffies_lock, seq)); |
906568c9 | 162 | |
d7eb231c | 163 | clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); |
906568c9 TG |
164 | |
165 | for (;;) { | |
d1748302 | 166 | if (!clockevents_program_event(dev, next, false)) |
906568c9 TG |
167 | return; |
168 | next = ktime_add(next, tick_period); | |
169 | } | |
170 | } | |
171 | } | |
172 | ||
173 | /* | |
174 | * Setup the tick device | |
175 | */ | |
176 | static void tick_setup_device(struct tick_device *td, | |
177 | struct clock_event_device *newdev, int cpu, | |
0de26520 | 178 | const struct cpumask *cpumask) |
906568c9 TG |
179 | { |
180 | ktime_t next_event; | |
181 | void (*handler)(struct clock_event_device *) = NULL; | |
182 | ||
183 | /* | |
184 | * First device setup ? | |
185 | */ | |
186 | if (!td->evtdev) { | |
187 | /* | |
188 | * If no cpu took the do_timer update, assign it to | |
189 | * this cpu: | |
190 | */ | |
6441402b | 191 | if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) { |
c5bfece2 | 192 | if (!tick_nohz_full_cpu(cpu)) |
a382bf93 FW |
193 | tick_do_timer_cpu = cpu; |
194 | else | |
195 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; | |
906568c9 TG |
196 | tick_next_period = ktime_get(); |
197 | tick_period = ktime_set(0, NSEC_PER_SEC / HZ); | |
198 | } | |
199 | ||
200 | /* | |
201 | * Startup in periodic mode first. | |
202 | */ | |
203 | td->mode = TICKDEV_MODE_PERIODIC; | |
204 | } else { | |
205 | handler = td->evtdev->event_handler; | |
206 | next_event = td->evtdev->next_event; | |
7c1e7689 | 207 | td->evtdev->event_handler = clockevents_handle_noop; |
906568c9 TG |
208 | } |
209 | ||
210 | td->evtdev = newdev; | |
211 | ||
212 | /* | |
213 | * When the device is not per cpu, pin the interrupt to the | |
214 | * current cpu: | |
215 | */ | |
320ab2b0 | 216 | if (!cpumask_equal(newdev->cpumask, cpumask)) |
0de26520 | 217 | irq_set_affinity(newdev->irq, cpumask); |
906568c9 | 218 | |
f8381cba TG |
219 | /* |
220 | * When global broadcasting is active, check if the current | |
221 | * device is registered as a placeholder for broadcast mode. | |
222 | * This allows us to handle this x86 misfeature in a generic | |
07bd1172 TG |
223 | * way. This function also returns !=0 when we keep the |
224 | * current active broadcast state for this CPU. | |
f8381cba TG |
225 | */ |
226 | if (tick_device_uses_broadcast(newdev, cpu)) | |
227 | return; | |
228 | ||
906568c9 TG |
229 | if (td->mode == TICKDEV_MODE_PERIODIC) |
230 | tick_setup_periodic(newdev, 0); | |
79bf2bb3 TG |
231 | else |
232 | tick_setup_oneshot(newdev, handler, next_event); | |
906568c9 TG |
233 | } |
234 | ||
03e13cf5 TG |
235 | void tick_install_replacement(struct clock_event_device *newdev) |
236 | { | |
22127e93 | 237 | struct tick_device *td = this_cpu_ptr(&tick_cpu_device); |
03e13cf5 TG |
238 | int cpu = smp_processor_id(); |
239 | ||
240 | clockevents_exchange_device(td->evtdev, newdev); | |
241 | tick_setup_device(td, newdev, cpu, cpumask_of(cpu)); | |
242 | if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) | |
243 | tick_oneshot_notify(); | |
244 | } | |
245 | ||
45cb8e01 TG |
246 | static bool tick_check_percpu(struct clock_event_device *curdev, |
247 | struct clock_event_device *newdev, int cpu) | |
248 | { | |
249 | if (!cpumask_test_cpu(cpu, newdev->cpumask)) | |
250 | return false; | |
251 | if (cpumask_equal(newdev->cpumask, cpumask_of(cpu))) | |
252 | return true; | |
253 | /* Check if irq affinity can be set */ | |
254 | if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq)) | |
255 | return false; | |
256 | /* Prefer an existing cpu local device */ | |
257 | if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu))) | |
258 | return false; | |
259 | return true; | |
260 | } | |
261 | ||
262 | static bool tick_check_preferred(struct clock_event_device *curdev, | |
263 | struct clock_event_device *newdev) | |
264 | { | |
265 | /* Prefer oneshot capable device */ | |
266 | if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) { | |
267 | if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT)) | |
268 | return false; | |
269 | if (tick_oneshot_mode_active()) | |
270 | return false; | |
271 | } | |
272 | ||
70e5975d SB |
273 | /* |
274 | * Use the higher rated one, but prefer a CPU local device with a lower | |
275 | * rating than a non-CPU local device | |
276 | */ | |
277 | return !curdev || | |
278 | newdev->rating > curdev->rating || | |
279 | !cpumask_equal(curdev->cpumask, newdev->cpumask); | |
45cb8e01 TG |
280 | } |
281 | ||
03e13cf5 TG |
282 | /* |
283 | * Check whether the new device is a better fit than curdev. curdev | |
284 | * can be NULL ! | |
285 | */ | |
286 | bool tick_check_replacement(struct clock_event_device *curdev, | |
287 | struct clock_event_device *newdev) | |
288 | { | |
521c4299 | 289 | if (!tick_check_percpu(curdev, newdev, smp_processor_id())) |
03e13cf5 TG |
290 | return false; |
291 | ||
292 | return tick_check_preferred(curdev, newdev); | |
293 | } | |
294 | ||
906568c9 | 295 | /* |
7126cac4 TG |
296 | * Check, if the new registered device should be used. Called with |
297 | * clockevents_lock held and interrupts disabled. | |
906568c9 | 298 | */ |
7172a286 | 299 | void tick_check_new_device(struct clock_event_device *newdev) |
906568c9 TG |
300 | { |
301 | struct clock_event_device *curdev; | |
302 | struct tick_device *td; | |
7172a286 | 303 | int cpu; |
906568c9 TG |
304 | |
305 | cpu = smp_processor_id(); | |
320ab2b0 | 306 | if (!cpumask_test_cpu(cpu, newdev->cpumask)) |
4a93232d | 307 | goto out_bc; |
906568c9 TG |
308 | |
309 | td = &per_cpu(tick_cpu_device, cpu); | |
310 | curdev = td->evtdev; | |
906568c9 TG |
311 | |
312 | /* cpu local device ? */ | |
45cb8e01 TG |
313 | if (!tick_check_percpu(curdev, newdev, cpu)) |
314 | goto out_bc; | |
906568c9 | 315 | |
45cb8e01 TG |
316 | /* Preference decision */ |
317 | if (!tick_check_preferred(curdev, newdev)) | |
318 | goto out_bc; | |
906568c9 | 319 | |
ccf33d68 TG |
320 | if (!try_module_get(newdev->owner)) |
321 | return; | |
322 | ||
906568c9 TG |
323 | /* |
324 | * Replace the eventually existing device by the new | |
f8381cba TG |
325 | * device. If the current device is the broadcast device, do |
326 | * not give it back to the clockevents layer ! | |
906568c9 | 327 | */ |
f8381cba | 328 | if (tick_is_broadcast_device(curdev)) { |
2344abbc | 329 | clockevents_shutdown(curdev); |
f8381cba TG |
330 | curdev = NULL; |
331 | } | |
906568c9 | 332 | clockevents_exchange_device(curdev, newdev); |
6b954823 | 333 | tick_setup_device(td, newdev, cpu, cpumask_of(cpu)); |
79bf2bb3 TG |
334 | if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) |
335 | tick_oneshot_notify(); | |
7172a286 | 336 | return; |
f8381cba TG |
337 | |
338 | out_bc: | |
339 | /* | |
340 | * Can the new device be used as a broadcast device ? | |
341 | */ | |
7172a286 | 342 | tick_install_broadcast_device(newdev); |
906568c9 TG |
343 | } |
344 | ||
52c063d1 | 345 | #ifdef CONFIG_HOTPLUG_CPU |
94df7de0 SD |
346 | /* |
347 | * Transfer the do_timer job away from a dying cpu. | |
348 | * | |
52c063d1 TG |
349 | * Called with interrupts disabled. Not locking required. If |
350 | * tick_do_timer_cpu is owned by this cpu, nothing can change it. | |
94df7de0 | 351 | */ |
52c063d1 | 352 | void tick_handover_do_timer(void) |
94df7de0 | 353 | { |
52c063d1 | 354 | if (tick_do_timer_cpu == smp_processor_id()) { |
94df7de0 SD |
355 | int cpu = cpumask_first(cpu_online_mask); |
356 | ||
357 | tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu : | |
358 | TICK_DO_TIMER_NONE; | |
359 | } | |
360 | } | |
361 | ||
906568c9 TG |
362 | /* |
363 | * Shutdown an event device on a given cpu: | |
364 | * | |
365 | * This is called on a life CPU, when a CPU is dead. So we cannot | |
366 | * access the hardware device itself. | |
367 | * We just set the mode and remove it from the lists. | |
368 | */ | |
a49b116d | 369 | void tick_shutdown(unsigned int cpu) |
906568c9 | 370 | { |
a49b116d | 371 | struct tick_device *td = &per_cpu(tick_cpu_device, cpu); |
906568c9 | 372 | struct clock_event_device *dev = td->evtdev; |
906568c9 | 373 | |
906568c9 TG |
374 | td->mode = TICKDEV_MODE_PERIODIC; |
375 | if (dev) { | |
376 | /* | |
377 | * Prevent that the clock events layer tries to call | |
378 | * the set mode function! | |
379 | */ | |
77e32c89 | 380 | dev->state = CLOCK_EVT_STATE_DETACHED; |
906568c9 TG |
381 | dev->mode = CLOCK_EVT_MODE_UNUSED; |
382 | clockevents_exchange_device(dev, NULL); | |
6f7a05d7 | 383 | dev->event_handler = clockevents_handle_noop; |
906568c9 TG |
384 | td->evtdev = NULL; |
385 | } | |
906568c9 | 386 | } |
a49b116d | 387 | #endif |
906568c9 | 388 | |
4ffee521 | 389 | /** |
f46481d0 | 390 | * tick_suspend_local - Suspend the local tick device |
4ffee521 | 391 | * |
f46481d0 | 392 | * Called from the local cpu for freeze with interrupts disabled. |
4ffee521 TG |
393 | * |
394 | * No locks required. Nothing can change the per cpu device. | |
395 | */ | |
7270d11c | 396 | void tick_suspend_local(void) |
6321dd60 | 397 | { |
22127e93 | 398 | struct tick_device *td = this_cpu_ptr(&tick_cpu_device); |
6321dd60 | 399 | |
2344abbc | 400 | clockevents_shutdown(td->evtdev); |
6321dd60 TG |
401 | } |
402 | ||
4ffee521 | 403 | /** |
f46481d0 | 404 | * tick_resume_local - Resume the local tick device |
4ffee521 | 405 | * |
f46481d0 | 406 | * Called from the local CPU for unfreeze or XEN resume magic. |
4ffee521 TG |
407 | * |
408 | * No locks required. Nothing can change the per cpu device. | |
409 | */ | |
f46481d0 | 410 | void tick_resume_local(void) |
6321dd60 | 411 | { |
f46481d0 TG |
412 | struct tick_device *td = this_cpu_ptr(&tick_cpu_device); |
413 | bool broadcast = tick_resume_check_broadcast(); | |
6321dd60 | 414 | |
554ef387 | 415 | clockevents_tick_resume(td->evtdev); |
18de5bc4 TG |
416 | if (!broadcast) { |
417 | if (td->mode == TICKDEV_MODE_PERIODIC) | |
418 | tick_setup_periodic(td->evtdev, 0); | |
419 | else | |
420 | tick_resume_oneshot(); | |
421 | } | |
6321dd60 TG |
422 | } |
423 | ||
f46481d0 TG |
424 | /** |
425 | * tick_suspend - Suspend the tick and the broadcast device | |
426 | * | |
427 | * Called from syscore_suspend() via timekeeping_suspend with only one | |
428 | * CPU online and interrupts disabled or from tick_unfreeze() under | |
429 | * tick_freeze_lock. | |
430 | * | |
431 | * No locks required. Nothing can change the per cpu device. | |
432 | */ | |
433 | void tick_suspend(void) | |
434 | { | |
435 | tick_suspend_local(); | |
436 | tick_suspend_broadcast(); | |
437 | } | |
438 | ||
439 | /** | |
440 | * tick_resume - Resume the tick and the broadcast device | |
441 | * | |
442 | * Called from syscore_resume() via timekeeping_resume with only one | |
443 | * CPU online and interrupts disabled. | |
444 | * | |
445 | * No locks required. Nothing can change the per cpu device. | |
446 | */ | |
447 | void tick_resume(void) | |
448 | { | |
449 | tick_resume_broadcast(); | |
450 | tick_resume_local(); | |
451 | } | |
452 | ||
124cf911 RW |
453 | static DEFINE_RAW_SPINLOCK(tick_freeze_lock); |
454 | static unsigned int tick_freeze_depth; | |
455 | ||
456 | /** | |
457 | * tick_freeze - Suspend the local tick and (possibly) timekeeping. | |
458 | * | |
459 | * Check if this is the last online CPU executing the function and if so, | |
460 | * suspend timekeeping. Otherwise suspend the local tick. | |
461 | * | |
462 | * Call with interrupts disabled. Must be balanced with %tick_unfreeze(). | |
463 | * Interrupts must not be enabled before the subsequent %tick_unfreeze(). | |
464 | */ | |
465 | void tick_freeze(void) | |
466 | { | |
467 | raw_spin_lock(&tick_freeze_lock); | |
468 | ||
469 | tick_freeze_depth++; | |
def74708 | 470 | if (tick_freeze_depth == num_online_cpus()) |
124cf911 | 471 | timekeeping_suspend(); |
def74708 | 472 | else |
f46481d0 | 473 | tick_suspend_local(); |
124cf911 RW |
474 | |
475 | raw_spin_unlock(&tick_freeze_lock); | |
476 | } | |
477 | ||
478 | /** | |
479 | * tick_unfreeze - Resume the local tick and (possibly) timekeeping. | |
480 | * | |
481 | * Check if this is the first CPU executing the function and if so, resume | |
482 | * timekeeping. Otherwise resume the local tick. | |
483 | * | |
484 | * Call with interrupts disabled. Must be balanced with %tick_freeze(). | |
485 | * Interrupts must not be enabled after the preceding %tick_freeze(). | |
486 | */ | |
487 | void tick_unfreeze(void) | |
488 | { | |
489 | raw_spin_lock(&tick_freeze_lock); | |
490 | ||
491 | if (tick_freeze_depth == num_online_cpus()) | |
492 | timekeeping_resume(); | |
493 | else | |
422fe750 | 494 | tick_resume_local(); |
124cf911 RW |
495 | |
496 | tick_freeze_depth--; | |
497 | ||
498 | raw_spin_unlock(&tick_freeze_lock); | |
499 | } | |
500 | ||
906568c9 TG |
501 | /** |
502 | * tick_init - initialize the tick control | |
906568c9 TG |
503 | */ |
504 | void __init tick_init(void) | |
505 | { | |
b352bc1c | 506 | tick_broadcast_init(); |
a80e49e2 | 507 | tick_nohz_init(); |
906568c9 | 508 | } |