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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
cf37b6b4 | 2 | /* |
a92057e1 IM |
3 | * Generic entry points for the idle threads and |
4 | * implementation of the idle task scheduling class. | |
5 | * | |
6 | * (NOTE: these are not related to SCHED_IDLE batch scheduled | |
7 | * tasks which are handled in sched/fair.c ) | |
cf37b6b4 | 8 | */ |
325ea10c | 9 | #include "sched.h" |
cf37b6b4 NP |
10 | |
11 | #include <trace/events/power.h> | |
12 | ||
6727ad9e CM |
13 | /* Linker adds these: start and end of __cpuidle functions */ |
14 | extern char __cpuidle_text_start[], __cpuidle_text_end[]; | |
15 | ||
faad3849 RW |
16 | /** |
17 | * sched_idle_set_state - Record idle state for the current CPU. | |
18 | * @idle_state: State to record. | |
19 | */ | |
20 | void sched_idle_set_state(struct cpuidle_state *idle_state) | |
21 | { | |
22 | idle_set_state(this_rq(), idle_state); | |
23 | } | |
24 | ||
cf37b6b4 NP |
25 | static int __read_mostly cpu_idle_force_poll; |
26 | ||
27 | void cpu_idle_poll_ctrl(bool enable) | |
28 | { | |
29 | if (enable) { | |
30 | cpu_idle_force_poll++; | |
31 | } else { | |
32 | cpu_idle_force_poll--; | |
33 | WARN_ON_ONCE(cpu_idle_force_poll < 0); | |
34 | } | |
35 | } | |
36 | ||
37 | #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP | |
38 | static int __init cpu_idle_poll_setup(char *__unused) | |
39 | { | |
40 | cpu_idle_force_poll = 1; | |
a92057e1 | 41 | |
cf37b6b4 NP |
42 | return 1; |
43 | } | |
44 | __setup("nohlt", cpu_idle_poll_setup); | |
45 | ||
46 | static int __init cpu_idle_nopoll_setup(char *__unused) | |
47 | { | |
48 | cpu_idle_force_poll = 0; | |
a92057e1 | 49 | |
cf37b6b4 NP |
50 | return 1; |
51 | } | |
52 | __setup("hlt", cpu_idle_nopoll_setup); | |
53 | #endif | |
54 | ||
6727ad9e | 55 | static noinline int __cpuidle cpu_idle_poll(void) |
cf37b6b4 | 56 | { |
1098582a PZ |
57 | trace_cpu_idle(0, smp_processor_id()); |
58 | stop_critical_timings(); | |
cf37b6b4 | 59 | rcu_idle_enter(); |
cf37b6b4 | 60 | local_irq_enable(); |
a92057e1 | 61 | |
ff6f2d29 | 62 | while (!tif_need_resched() && |
1098582a | 63 | (cpu_idle_force_poll || tick_check_broadcast_expired())) |
cf37b6b4 | 64 | cpu_relax(); |
1098582a | 65 | |
cf37b6b4 | 66 | rcu_idle_exit(); |
1098582a PZ |
67 | start_critical_timings(); |
68 | trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id()); | |
a92057e1 | 69 | |
cf37b6b4 NP |
70 | return 1; |
71 | } | |
72 | ||
73 | /* Weak implementations for optional arch specific functions */ | |
74 | void __weak arch_cpu_idle_prepare(void) { } | |
75 | void __weak arch_cpu_idle_enter(void) { } | |
76 | void __weak arch_cpu_idle_exit(void) { } | |
77 | void __weak arch_cpu_idle_dead(void) { } | |
78 | void __weak arch_cpu_idle(void) | |
79 | { | |
80 | cpu_idle_force_poll = 1; | |
81 | local_irq_enable(); | |
82 | } | |
83 | ||
827a5aef RW |
84 | /** |
85 | * default_idle_call - Default CPU idle routine. | |
86 | * | |
87 | * To use when the cpuidle framework cannot be used. | |
88 | */ | |
6727ad9e | 89 | void __cpuidle default_idle_call(void) |
82f66327 | 90 | { |
63caae84 | 91 | if (current_clr_polling_and_test()) { |
82f66327 | 92 | local_irq_enable(); |
63caae84 | 93 | } else { |
9864f5b5 PZ |
94 | |
95 | trace_cpu_idle(1, smp_processor_id()); | |
63caae84 | 96 | stop_critical_timings(); |
1098582a | 97 | rcu_idle_enter(); |
82f66327 | 98 | arch_cpu_idle(); |
1098582a | 99 | rcu_idle_exit(); |
63caae84 | 100 | start_critical_timings(); |
9864f5b5 | 101 | trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id()); |
63caae84 | 102 | } |
82f66327 RW |
103 | } |
104 | ||
10e8b11e RW |
105 | static int call_cpuidle_s2idle(struct cpuidle_driver *drv, |
106 | struct cpuidle_device *dev) | |
107 | { | |
108 | if (current_clr_polling_and_test()) | |
109 | return -EBUSY; | |
110 | ||
111 | return cpuidle_enter_s2idle(drv, dev); | |
112 | } | |
113 | ||
bcf6ad8a RW |
114 | static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev, |
115 | int next_state) | |
116 | { | |
bcf6ad8a RW |
117 | /* |
118 | * The idle task must be scheduled, it is pointless to go to idle, just | |
119 | * update no idle residency and return. | |
120 | */ | |
121 | if (current_clr_polling_and_test()) { | |
c1d51f68 | 122 | dev->last_residency_ns = 0; |
bcf6ad8a RW |
123 | local_irq_enable(); |
124 | return -EBUSY; | |
125 | } | |
126 | ||
bcf6ad8a RW |
127 | /* |
128 | * Enter the idle state previously returned by the governor decision. | |
129 | * This function will block until an interrupt occurs and will take | |
130 | * care of re-enabling the local interrupts | |
131 | */ | |
827a5aef | 132 | return cpuidle_enter(drv, dev, next_state); |
bcf6ad8a RW |
133 | } |
134 | ||
30cdd69e DL |
135 | /** |
136 | * cpuidle_idle_call - the main idle function | |
137 | * | |
138 | * NOTE: no locks or semaphores should be used here | |
82c65d60 AL |
139 | * |
140 | * On archs that support TIF_POLLING_NRFLAG, is called with polling | |
141 | * set, and it returns with polling set. If it ever stops polling, it | |
142 | * must clear the polling bit. | |
30cdd69e | 143 | */ |
08c373e5 | 144 | static void cpuidle_idle_call(void) |
30cdd69e | 145 | { |
9bd616e3 | 146 | struct cpuidle_device *dev = cpuidle_get_device(); |
30cdd69e | 147 | struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); |
37352273 | 148 | int next_state, entered_state; |
30cdd69e | 149 | |
a1d028bd DL |
150 | /* |
151 | * Check if the idle task must be rescheduled. If it is the | |
c444117f | 152 | * case, exit the function after re-enabling the local irq. |
a1d028bd | 153 | */ |
c444117f | 154 | if (need_resched()) { |
8ca3c642 | 155 | local_irq_enable(); |
08c373e5 | 156 | return; |
8ca3c642 DL |
157 | } |
158 | ||
a1d028bd | 159 | /* |
ed98c349 RW |
160 | * The RCU framework needs to be told that we are entering an idle |
161 | * section, so no more rcu read side critical sections and one more | |
a1d028bd DL |
162 | * step to the grace period |
163 | */ | |
c8cc7d4d | 164 | |
82f66327 | 165 | if (cpuidle_not_available(drv, dev)) { |
ed98c349 | 166 | tick_nohz_idle_stop_tick(); |
ed98c349 | 167 | |
82f66327 RW |
168 | default_idle_call(); |
169 | goto exit_idle; | |
170 | } | |
ef2b22ac | 171 | |
38106313 | 172 | /* |
f02f4f9d | 173 | * Suspend-to-idle ("s2idle") is a system state in which all user space |
38106313 | 174 | * has been frozen, all I/O devices have been suspended and the only |
3e0de271 | 175 | * activity happens here and in interrupts (if any). In that case bypass |
38106313 RW |
176 | * the cpuidle governor and go stratight for the deepest idle state |
177 | * available. Possibly also suspend the local tick and the entire | |
178 | * timekeeping to prevent timer interrupts from kicking us out of idle | |
179 | * until a proper wakeup interrupt happens. | |
180 | */ | |
bb8313b6 | 181 | |
c55b51a0 | 182 | if (idle_should_enter_s2idle() || dev->forced_idle_latency_limit_ns) { |
5aa9ba63 DL |
183 | u64 max_latency_ns; |
184 | ||
f02f4f9d | 185 | if (idle_should_enter_s2idle()) { |
ed98c349 | 186 | |
10e8b11e RW |
187 | entered_state = call_cpuidle_s2idle(drv, dev); |
188 | if (entered_state > 0) | |
bb8313b6 | 189 | goto exit_idle; |
ed98c349 | 190 | |
5aa9ba63 DL |
191 | max_latency_ns = U64_MAX; |
192 | } else { | |
193 | max_latency_ns = dev->forced_idle_latency_limit_ns; | |
ef2b22ac RW |
194 | } |
195 | ||
ed98c349 | 196 | tick_nohz_idle_stop_tick(); |
ed98c349 | 197 | |
5aa9ba63 | 198 | next_state = cpuidle_find_deepest_state(drv, dev, max_latency_ns); |
bcf6ad8a | 199 | call_cpuidle(drv, dev, next_state); |
ef2b22ac | 200 | } else { |
45f1ff59 RW |
201 | bool stop_tick = true; |
202 | ||
ef2b22ac RW |
203 | /* |
204 | * Ask the cpuidle framework to choose a convenient idle state. | |
205 | */ | |
45f1ff59 | 206 | next_state = cpuidle_select(drv, dev, &stop_tick); |
554c8aa8 | 207 | |
7059b366 | 208 | if (stop_tick || tick_nohz_tick_stopped()) |
554c8aa8 RW |
209 | tick_nohz_idle_stop_tick(); |
210 | else | |
211 | tick_nohz_idle_retain_tick(); | |
212 | ||
bcf6ad8a RW |
213 | entered_state = call_cpuidle(drv, dev, next_state); |
214 | /* | |
215 | * Give the governor an opportunity to reflect on the outcome | |
216 | */ | |
ef2b22ac | 217 | cpuidle_reflect(dev, entered_state); |
bcf6ad8a | 218 | } |
37352273 PZ |
219 | |
220 | exit_idle: | |
8ca3c642 | 221 | __current_set_polling(); |
30cdd69e | 222 | |
a1d028bd | 223 | /* |
37352273 | 224 | * It is up to the idle functions to reenable local interrupts |
a1d028bd | 225 | */ |
c8cc7d4d DL |
226 | if (WARN_ON_ONCE(irqs_disabled())) |
227 | local_irq_enable(); | |
30cdd69e | 228 | } |
30cdd69e | 229 | |
cf37b6b4 NP |
230 | /* |
231 | * Generic idle loop implementation | |
82c65d60 AL |
232 | * |
233 | * Called with polling cleared. | |
cf37b6b4 | 234 | */ |
c1de45ca | 235 | static void do_idle(void) |
cf37b6b4 | 236 | { |
54b933c6 | 237 | int cpu = smp_processor_id(); |
c1de45ca PZ |
238 | /* |
239 | * If the arch has a polling bit, we maintain an invariant: | |
240 | * | |
241 | * Our polling bit is clear if we're not scheduled (i.e. if rq->curr != | |
242 | * rq->idle). This means that, if rq->idle has the polling bit set, | |
243 | * then setting need_resched is guaranteed to cause the CPU to | |
244 | * reschedule. | |
245 | */ | |
cf37b6b4 | 246 | |
c1de45ca PZ |
247 | __current_set_polling(); |
248 | tick_nohz_idle_enter(); | |
cf37b6b4 | 249 | |
c1de45ca | 250 | while (!need_resched()) { |
c1de45ca | 251 | rmb(); |
cf37b6b4 | 252 | |
e78a7614 PZ |
253 | local_irq_disable(); |
254 | ||
54b933c6 | 255 | if (cpu_is_offline(cpu)) { |
e78a7614 | 256 | tick_nohz_idle_stop_tick(); |
c1de45ca PZ |
257 | cpuhp_report_idle_dead(); |
258 | arch_cpu_idle_dead(); | |
cf37b6b4 | 259 | } |
06d50c65 | 260 | |
c1de45ca | 261 | arch_cpu_idle_enter(); |
82c65d60 AL |
262 | |
263 | /* | |
c1de45ca PZ |
264 | * In poll mode we reenable interrupts and spin. Also if we |
265 | * detected in the wakeup from idle path that the tick | |
266 | * broadcast device expired for us, we don't want to go deep | |
267 | * idle as we know that the IPI is going to arrive right away. | |
82c65d60 | 268 | */ |
2aaf709a RW |
269 | if (cpu_idle_force_poll || tick_check_broadcast_expired()) { |
270 | tick_nohz_idle_restart_tick(); | |
c1de45ca | 271 | cpu_idle_poll(); |
2aaf709a | 272 | } else { |
c1de45ca | 273 | cpuidle_idle_call(); |
2aaf709a | 274 | } |
c1de45ca | 275 | arch_cpu_idle_exit(); |
cf37b6b4 | 276 | } |
c1de45ca PZ |
277 | |
278 | /* | |
279 | * Since we fell out of the loop above, we know TIF_NEED_RESCHED must | |
280 | * be set, propagate it into PREEMPT_NEED_RESCHED. | |
281 | * | |
282 | * This is required because for polling idle loops we will not have had | |
283 | * an IPI to fold the state for us. | |
284 | */ | |
285 | preempt_set_need_resched(); | |
286 | tick_nohz_idle_exit(); | |
287 | __current_clr_polling(); | |
288 | ||
289 | /* | |
290 | * We promise to call sched_ttwu_pending() and reschedule if | |
291 | * need_resched() is set while polling is set. That means that clearing | |
292 | * polling needs to be visible before doing these things. | |
293 | */ | |
294 | smp_mb__after_atomic(); | |
295 | ||
b2a02fc4 PZ |
296 | /* |
297 | * RCU relies on this call to be done outside of an RCU read-side | |
298 | * critical section. | |
299 | */ | |
300 | flush_smp_call_function_from_idle(); | |
8663effb | 301 | schedule_idle(); |
d83a7cb3 JP |
302 | |
303 | if (unlikely(klp_patch_pending(current))) | |
304 | klp_update_patch_state(current); | |
cf37b6b4 NP |
305 | } |
306 | ||
6727ad9e CM |
307 | bool cpu_in_idle(unsigned long pc) |
308 | { | |
309 | return pc >= (unsigned long)__cpuidle_text_start && | |
310 | pc < (unsigned long)__cpuidle_text_end; | |
311 | } | |
312 | ||
c1de45ca PZ |
313 | struct idle_timer { |
314 | struct hrtimer timer; | |
315 | int done; | |
316 | }; | |
317 | ||
318 | static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer) | |
319 | { | |
320 | struct idle_timer *it = container_of(timer, struct idle_timer, timer); | |
321 | ||
322 | WRITE_ONCE(it->done, 1); | |
323 | set_tsk_need_resched(current); | |
324 | ||
325 | return HRTIMER_NORESTART; | |
326 | } | |
327 | ||
c55b51a0 | 328 | void play_idle_precise(u64 duration_ns, u64 latency_ns) |
c1de45ca PZ |
329 | { |
330 | struct idle_timer it; | |
331 | ||
332 | /* | |
333 | * Only FIFO tasks can disable the tick since they don't need the forced | |
334 | * preemption. | |
335 | */ | |
336 | WARN_ON_ONCE(current->policy != SCHED_FIFO); | |
337 | WARN_ON_ONCE(current->nr_cpus_allowed != 1); | |
338 | WARN_ON_ONCE(!(current->flags & PF_KTHREAD)); | |
339 | WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY)); | |
c55b51a0 | 340 | WARN_ON_ONCE(!duration_ns); |
c1de45ca PZ |
341 | |
342 | rcu_sleep_check(); | |
343 | preempt_disable(); | |
344 | current->flags |= PF_IDLE; | |
c55b51a0 | 345 | cpuidle_use_deepest_state(latency_ns); |
c1de45ca PZ |
346 | |
347 | it.done = 0; | |
348 | hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
349 | it.timer.function = idle_inject_timer_fn; | |
c55b51a0 | 350 | hrtimer_start(&it.timer, ns_to_ktime(duration_ns), |
82e430a6 | 351 | HRTIMER_MODE_REL_PINNED); |
c1de45ca PZ |
352 | |
353 | while (!READ_ONCE(it.done)) | |
354 | do_idle(); | |
355 | ||
c55b51a0 | 356 | cpuidle_use_deepest_state(0); |
c1de45ca PZ |
357 | current->flags &= ~PF_IDLE; |
358 | ||
359 | preempt_fold_need_resched(); | |
360 | preempt_enable(); | |
361 | } | |
c55b51a0 | 362 | EXPORT_SYMBOL_GPL(play_idle_precise); |
c1de45ca | 363 | |
cf37b6b4 NP |
364 | void cpu_startup_entry(enum cpuhp_state state) |
365 | { | |
cf37b6b4 | 366 | arch_cpu_idle_prepare(); |
8df3e07e | 367 | cpuhp_online_idle(state); |
c1de45ca PZ |
368 | while (1) |
369 | do_idle(); | |
cf37b6b4 | 370 | } |
a92057e1 IM |
371 | |
372 | /* | |
373 | * idle-task scheduling class. | |
374 | */ | |
375 | ||
376 | #ifdef CONFIG_SMP | |
377 | static int | |
378 | select_task_rq_idle(struct task_struct *p, int cpu, int sd_flag, int flags) | |
379 | { | |
380 | return task_cpu(p); /* IDLE tasks as never migrated */ | |
381 | } | |
6e2df058 PZ |
382 | |
383 | static int | |
384 | balance_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) | |
385 | { | |
386 | return WARN_ON_ONCE(1); | |
387 | } | |
a92057e1 IM |
388 | #endif |
389 | ||
390 | /* | |
391 | * Idle tasks are unconditionally rescheduled: | |
392 | */ | |
393 | static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags) | |
394 | { | |
395 | resched_curr(rq); | |
396 | } | |
397 | ||
6e2df058 | 398 | static void put_prev_task_idle(struct rq *rq, struct task_struct *prev) |
03b7fad1 PZ |
399 | { |
400 | } | |
401 | ||
a0e813f2 | 402 | static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool first) |
a92057e1 | 403 | { |
a92057e1 IM |
404 | update_idle_core(rq); |
405 | schedstat_inc(rq->sched_goidle); | |
03b7fad1 PZ |
406 | } |
407 | ||
98c2f700 | 408 | struct task_struct *pick_next_task_idle(struct rq *rq) |
a92057e1 | 409 | { |
03b7fad1 PZ |
410 | struct task_struct *next = rq->idle; |
411 | ||
a0e813f2 | 412 | set_next_task_idle(rq, next, true); |
a92057e1 | 413 | |
03b7fad1 | 414 | return next; |
a92057e1 IM |
415 | } |
416 | ||
417 | /* | |
418 | * It is not legal to sleep in the idle task - print a warning | |
419 | * message if some code attempts to do it: | |
420 | */ | |
421 | static void | |
422 | dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags) | |
423 | { | |
424 | raw_spin_unlock_irq(&rq->lock); | |
425 | printk(KERN_ERR "bad: scheduling from the idle thread!\n"); | |
426 | dump_stack(); | |
427 | raw_spin_lock_irq(&rq->lock); | |
428 | } | |
429 | ||
a92057e1 IM |
430 | /* |
431 | * scheduler tick hitting a task of our scheduling class. | |
432 | * | |
433 | * NOTE: This function can be called remotely by the tick offload that | |
434 | * goes along full dynticks. Therefore no local assumption can be made | |
435 | * and everything must be accessed through the @rq and @curr passed in | |
436 | * parameters. | |
437 | */ | |
438 | static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued) | |
439 | { | |
440 | } | |
441 | ||
a92057e1 IM |
442 | static void switched_to_idle(struct rq *rq, struct task_struct *p) |
443 | { | |
444 | BUG(); | |
445 | } | |
446 | ||
447 | static void | |
448 | prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio) | |
449 | { | |
450 | BUG(); | |
451 | } | |
452 | ||
a92057e1 IM |
453 | static void update_curr_idle(struct rq *rq) |
454 | { | |
455 | } | |
456 | ||
457 | /* | |
458 | * Simple, special scheduling class for the per-CPU idle tasks: | |
459 | */ | |
590d6979 SRV |
460 | const struct sched_class idle_sched_class |
461 | __attribute__((section("__idle_sched_class"))) = { | |
a92057e1 IM |
462 | /* no enqueue/yield_task for idle tasks */ |
463 | ||
464 | /* dequeue is not valid, we print a debug message there: */ | |
465 | .dequeue_task = dequeue_task_idle, | |
466 | ||
467 | .check_preempt_curr = check_preempt_curr_idle, | |
468 | ||
469 | .pick_next_task = pick_next_task_idle, | |
470 | .put_prev_task = put_prev_task_idle, | |
03b7fad1 | 471 | .set_next_task = set_next_task_idle, |
a92057e1 IM |
472 | |
473 | #ifdef CONFIG_SMP | |
6e2df058 | 474 | .balance = balance_idle, |
a92057e1 IM |
475 | .select_task_rq = select_task_rq_idle, |
476 | .set_cpus_allowed = set_cpus_allowed_common, | |
477 | #endif | |
478 | ||
a92057e1 IM |
479 | .task_tick = task_tick_idle, |
480 | ||
a92057e1 IM |
481 | .prio_changed = prio_changed_idle, |
482 | .switched_to = switched_to_idle, | |
483 | .update_curr = update_curr_idle, | |
484 | }; |