Commit | Line | Data |
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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 | */ |
cf37b6b4 | 9 | |
6727ad9e CM |
10 | /* Linker adds these: start and end of __cpuidle functions */ |
11 | extern char __cpuidle_text_start[], __cpuidle_text_end[]; | |
12 | ||
faad3849 RW |
13 | /** |
14 | * sched_idle_set_state - Record idle state for the current CPU. | |
15 | * @idle_state: State to record. | |
16 | */ | |
17 | void sched_idle_set_state(struct cpuidle_state *idle_state) | |
18 | { | |
19 | idle_set_state(this_rq(), idle_state); | |
20 | } | |
21 | ||
cf37b6b4 NP |
22 | static int __read_mostly cpu_idle_force_poll; |
23 | ||
24 | void cpu_idle_poll_ctrl(bool enable) | |
25 | { | |
26 | if (enable) { | |
27 | cpu_idle_force_poll++; | |
28 | } else { | |
29 | cpu_idle_force_poll--; | |
30 | WARN_ON_ONCE(cpu_idle_force_poll < 0); | |
31 | } | |
32 | } | |
33 | ||
34 | #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP | |
35 | static int __init cpu_idle_poll_setup(char *__unused) | |
36 | { | |
37 | cpu_idle_force_poll = 1; | |
a92057e1 | 38 | |
cf37b6b4 NP |
39 | return 1; |
40 | } | |
41 | __setup("nohlt", cpu_idle_poll_setup); | |
42 | ||
43 | static int __init cpu_idle_nopoll_setup(char *__unused) | |
44 | { | |
45 | cpu_idle_force_poll = 0; | |
a92057e1 | 46 | |
cf37b6b4 NP |
47 | return 1; |
48 | } | |
49 | __setup("hlt", cpu_idle_nopoll_setup); | |
50 | #endif | |
51 | ||
6727ad9e | 52 | static noinline int __cpuidle cpu_idle_poll(void) |
cf37b6b4 | 53 | { |
a01353cf | 54 | instrumentation_begin(); |
1098582a PZ |
55 | trace_cpu_idle(0, smp_processor_id()); |
56 | stop_critical_timings(); | |
a01353cf | 57 | ct_cpuidle_enter(); |
a92057e1 | 58 | |
a01353cf | 59 | raw_local_irq_enable(); |
ff6f2d29 | 60 | while (!tif_need_resched() && |
1098582a | 61 | (cpu_idle_force_poll || tick_check_broadcast_expired())) |
cf37b6b4 | 62 | cpu_relax(); |
a01353cf | 63 | raw_local_irq_disable(); |
1098582a | 64 | |
a01353cf | 65 | ct_cpuidle_exit(); |
1098582a PZ |
66 | start_critical_timings(); |
67 | trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id()); | |
a01353cf PZ |
68 | local_irq_enable(); |
69 | instrumentation_end(); | |
a92057e1 | 70 | |
cf37b6b4 NP |
71 | return 1; |
72 | } | |
73 | ||
74 | /* Weak implementations for optional arch specific functions */ | |
75 | void __weak arch_cpu_idle_prepare(void) { } | |
76 | void __weak arch_cpu_idle_enter(void) { } | |
77 | void __weak arch_cpu_idle_exit(void) { } | |
071c44e4 | 78 | void __weak __noreturn arch_cpu_idle_dead(void) { while (1); } |
cf37b6b4 NP |
79 | void __weak arch_cpu_idle(void) |
80 | { | |
81 | cpu_idle_force_poll = 1; | |
cf37b6b4 NP |
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 | { |
a01353cf PZ |
91 | instrumentation_begin(); |
92 | if (!current_clr_polling_and_test()) { | |
9864f5b5 | 93 | trace_cpu_idle(1, smp_processor_id()); |
63caae84 | 94 | stop_critical_timings(); |
58c644ba | 95 | |
a01353cf | 96 | ct_cpuidle_enter(); |
82f66327 | 97 | arch_cpu_idle(); |
a01353cf | 98 | ct_cpuidle_exit(); |
58c644ba | 99 | |
63caae84 | 100 | start_critical_timings(); |
9864f5b5 | 101 | trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id()); |
63caae84 | 102 | } |
a01353cf PZ |
103 | local_irq_enable(); |
104 | instrumentation_end(); | |
82f66327 RW |
105 | } |
106 | ||
10e8b11e RW |
107 | static int call_cpuidle_s2idle(struct cpuidle_driver *drv, |
108 | struct cpuidle_device *dev) | |
109 | { | |
110 | if (current_clr_polling_and_test()) | |
111 | return -EBUSY; | |
112 | ||
113 | return cpuidle_enter_s2idle(drv, dev); | |
114 | } | |
115 | ||
bcf6ad8a RW |
116 | static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev, |
117 | int next_state) | |
118 | { | |
bcf6ad8a RW |
119 | /* |
120 | * The idle task must be scheduled, it is pointless to go to idle, just | |
121 | * update no idle residency and return. | |
122 | */ | |
123 | if (current_clr_polling_and_test()) { | |
c1d51f68 | 124 | dev->last_residency_ns = 0; |
bcf6ad8a RW |
125 | local_irq_enable(); |
126 | return -EBUSY; | |
127 | } | |
128 | ||
bcf6ad8a RW |
129 | /* |
130 | * Enter the idle state previously returned by the governor decision. | |
131 | * This function will block until an interrupt occurs and will take | |
132 | * care of re-enabling the local interrupts | |
133 | */ | |
827a5aef | 134 | return cpuidle_enter(drv, dev, next_state); |
bcf6ad8a RW |
135 | } |
136 | ||
30cdd69e DL |
137 | /** |
138 | * cpuidle_idle_call - the main idle function | |
139 | * | |
140 | * NOTE: no locks or semaphores should be used here | |
82c65d60 | 141 | * |
3b03706f | 142 | * On architectures that support TIF_POLLING_NRFLAG, is called with polling |
82c65d60 AL |
143 | * set, and it returns with polling set. If it ever stops polling, it |
144 | * must clear the polling bit. | |
30cdd69e | 145 | */ |
08c373e5 | 146 | static void cpuidle_idle_call(void) |
30cdd69e | 147 | { |
9bd616e3 | 148 | struct cpuidle_device *dev = cpuidle_get_device(); |
30cdd69e | 149 | struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); |
37352273 | 150 | int next_state, entered_state; |
30cdd69e | 151 | |
a1d028bd DL |
152 | /* |
153 | * Check if the idle task must be rescheduled. If it is the | |
c444117f | 154 | * case, exit the function after re-enabling the local irq. |
a1d028bd | 155 | */ |
c444117f | 156 | if (need_resched()) { |
8ca3c642 | 157 | local_irq_enable(); |
08c373e5 | 158 | return; |
8ca3c642 DL |
159 | } |
160 | ||
a1d028bd | 161 | /* |
ed98c349 RW |
162 | * The RCU framework needs to be told that we are entering an idle |
163 | * section, so no more rcu read side critical sections and one more | |
a1d028bd DL |
164 | * step to the grace period |
165 | */ | |
c8cc7d4d | 166 | |
82f66327 | 167 | if (cpuidle_not_available(drv, dev)) { |
ed98c349 | 168 | tick_nohz_idle_stop_tick(); |
ed98c349 | 169 | |
82f66327 RW |
170 | default_idle_call(); |
171 | goto exit_idle; | |
172 | } | |
ef2b22ac | 173 | |
38106313 | 174 | /* |
f02f4f9d | 175 | * Suspend-to-idle ("s2idle") is a system state in which all user space |
38106313 | 176 | * has been frozen, all I/O devices have been suspended and the only |
3e0de271 | 177 | * activity happens here and in interrupts (if any). In that case bypass |
3b03706f | 178 | * the cpuidle governor and go straight for the deepest idle state |
38106313 RW |
179 | * available. Possibly also suspend the local tick and the entire |
180 | * timekeeping to prevent timer interrupts from kicking us out of idle | |
181 | * until a proper wakeup interrupt happens. | |
182 | */ | |
bb8313b6 | 183 | |
c55b51a0 | 184 | if (idle_should_enter_s2idle() || dev->forced_idle_latency_limit_ns) { |
5aa9ba63 DL |
185 | u64 max_latency_ns; |
186 | ||
f02f4f9d | 187 | if (idle_should_enter_s2idle()) { |
ed98c349 | 188 | |
10e8b11e RW |
189 | entered_state = call_cpuidle_s2idle(drv, dev); |
190 | if (entered_state > 0) | |
bb8313b6 | 191 | goto exit_idle; |
ed98c349 | 192 | |
5aa9ba63 DL |
193 | max_latency_ns = U64_MAX; |
194 | } else { | |
195 | max_latency_ns = dev->forced_idle_latency_limit_ns; | |
ef2b22ac RW |
196 | } |
197 | ||
ed98c349 | 198 | tick_nohz_idle_stop_tick(); |
ed98c349 | 199 | |
5aa9ba63 | 200 | next_state = cpuidle_find_deepest_state(drv, dev, max_latency_ns); |
bcf6ad8a | 201 | call_cpuidle(drv, dev, next_state); |
ef2b22ac | 202 | } else { |
45f1ff59 RW |
203 | bool stop_tick = true; |
204 | ||
ef2b22ac RW |
205 | /* |
206 | * Ask the cpuidle framework to choose a convenient idle state. | |
207 | */ | |
45f1ff59 | 208 | next_state = cpuidle_select(drv, dev, &stop_tick); |
554c8aa8 | 209 | |
7059b366 | 210 | if (stop_tick || tick_nohz_tick_stopped()) |
554c8aa8 RW |
211 | tick_nohz_idle_stop_tick(); |
212 | else | |
213 | tick_nohz_idle_retain_tick(); | |
214 | ||
bcf6ad8a RW |
215 | entered_state = call_cpuidle(drv, dev, next_state); |
216 | /* | |
217 | * Give the governor an opportunity to reflect on the outcome | |
218 | */ | |
ef2b22ac | 219 | cpuidle_reflect(dev, entered_state); |
bcf6ad8a | 220 | } |
37352273 PZ |
221 | |
222 | exit_idle: | |
8ca3c642 | 223 | __current_set_polling(); |
30cdd69e | 224 | |
a1d028bd | 225 | /* |
37352273 | 226 | * It is up to the idle functions to reenable local interrupts |
a1d028bd | 227 | */ |
c8cc7d4d DL |
228 | if (WARN_ON_ONCE(irqs_disabled())) |
229 | local_irq_enable(); | |
30cdd69e | 230 | } |
30cdd69e | 231 | |
cf37b6b4 NP |
232 | /* |
233 | * Generic idle loop implementation | |
82c65d60 AL |
234 | * |
235 | * Called with polling cleared. | |
cf37b6b4 | 236 | */ |
c1de45ca | 237 | static void do_idle(void) |
cf37b6b4 | 238 | { |
54b933c6 | 239 | int cpu = smp_processor_id(); |
c6f88654 VG |
240 | |
241 | /* | |
242 | * Check if we need to update blocked load | |
243 | */ | |
244 | nohz_run_idle_balance(cpu); | |
245 | ||
c1de45ca PZ |
246 | /* |
247 | * If the arch has a polling bit, we maintain an invariant: | |
248 | * | |
249 | * Our polling bit is clear if we're not scheduled (i.e. if rq->curr != | |
250 | * rq->idle). This means that, if rq->idle has the polling bit set, | |
251 | * then setting need_resched is guaranteed to cause the CPU to | |
252 | * reschedule. | |
253 | */ | |
cf37b6b4 | 254 | |
c1de45ca PZ |
255 | __current_set_polling(); |
256 | tick_nohz_idle_enter(); | |
cf37b6b4 | 257 | |
c1de45ca | 258 | while (!need_resched()) { |
c1de45ca | 259 | rmb(); |
cf37b6b4 | 260 | |
e78a7614 PZ |
261 | local_irq_disable(); |
262 | ||
54b933c6 | 263 | if (cpu_is_offline(cpu)) { |
e78a7614 | 264 | tick_nohz_idle_stop_tick(); |
c1de45ca PZ |
265 | cpuhp_report_idle_dead(); |
266 | arch_cpu_idle_dead(); | |
cf37b6b4 | 267 | } |
06d50c65 | 268 | |
c1de45ca | 269 | arch_cpu_idle_enter(); |
43789ef3 | 270 | rcu_nocb_flush_deferred_wakeup(); |
82c65d60 AL |
271 | |
272 | /* | |
c1de45ca PZ |
273 | * In poll mode we reenable interrupts and spin. Also if we |
274 | * detected in the wakeup from idle path that the tick | |
275 | * broadcast device expired for us, we don't want to go deep | |
276 | * idle as we know that the IPI is going to arrive right away. | |
82c65d60 | 277 | */ |
2aaf709a RW |
278 | if (cpu_idle_force_poll || tick_check_broadcast_expired()) { |
279 | tick_nohz_idle_restart_tick(); | |
c1de45ca | 280 | cpu_idle_poll(); |
2aaf709a | 281 | } else { |
c1de45ca | 282 | cpuidle_idle_call(); |
2aaf709a | 283 | } |
c1de45ca | 284 | arch_cpu_idle_exit(); |
cf37b6b4 | 285 | } |
c1de45ca PZ |
286 | |
287 | /* | |
288 | * Since we fell out of the loop above, we know TIF_NEED_RESCHED must | |
289 | * be set, propagate it into PREEMPT_NEED_RESCHED. | |
290 | * | |
291 | * This is required because for polling idle loops we will not have had | |
292 | * an IPI to fold the state for us. | |
293 | */ | |
294 | preempt_set_need_resched(); | |
295 | tick_nohz_idle_exit(); | |
296 | __current_clr_polling(); | |
297 | ||
298 | /* | |
299 | * We promise to call sched_ttwu_pending() and reschedule if | |
300 | * need_resched() is set while polling is set. That means that clearing | |
301 | * polling needs to be visible before doing these things. | |
302 | */ | |
303 | smp_mb__after_atomic(); | |
304 | ||
b2a02fc4 PZ |
305 | /* |
306 | * RCU relies on this call to be done outside of an RCU read-side | |
307 | * critical section. | |
308 | */ | |
16bf5a5e | 309 | flush_smp_call_function_queue(); |
8663effb | 310 | schedule_idle(); |
d83a7cb3 JP |
311 | |
312 | if (unlikely(klp_patch_pending(current))) | |
313 | klp_update_patch_state(current); | |
cf37b6b4 NP |
314 | } |
315 | ||
6727ad9e CM |
316 | bool cpu_in_idle(unsigned long pc) |
317 | { | |
318 | return pc >= (unsigned long)__cpuidle_text_start && | |
319 | pc < (unsigned long)__cpuidle_text_end; | |
320 | } | |
321 | ||
c1de45ca PZ |
322 | struct idle_timer { |
323 | struct hrtimer timer; | |
324 | int done; | |
325 | }; | |
326 | ||
327 | static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer) | |
328 | { | |
329 | struct idle_timer *it = container_of(timer, struct idle_timer, timer); | |
330 | ||
331 | WRITE_ONCE(it->done, 1); | |
332 | set_tsk_need_resched(current); | |
333 | ||
334 | return HRTIMER_NORESTART; | |
335 | } | |
336 | ||
c55b51a0 | 337 | void play_idle_precise(u64 duration_ns, u64 latency_ns) |
c1de45ca PZ |
338 | { |
339 | struct idle_timer it; | |
340 | ||
341 | /* | |
342 | * Only FIFO tasks can disable the tick since they don't need the forced | |
343 | * preemption. | |
344 | */ | |
345 | WARN_ON_ONCE(current->policy != SCHED_FIFO); | |
346 | WARN_ON_ONCE(current->nr_cpus_allowed != 1); | |
347 | WARN_ON_ONCE(!(current->flags & PF_KTHREAD)); | |
348 | WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY)); | |
c55b51a0 | 349 | WARN_ON_ONCE(!duration_ns); |
618758ed | 350 | WARN_ON_ONCE(current->mm); |
c1de45ca PZ |
351 | |
352 | rcu_sleep_check(); | |
353 | preempt_disable(); | |
354 | current->flags |= PF_IDLE; | |
c55b51a0 | 355 | cpuidle_use_deepest_state(latency_ns); |
c1de45ca PZ |
356 | |
357 | it.done = 0; | |
98484179 | 358 | hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); |
c1de45ca | 359 | it.timer.function = idle_inject_timer_fn; |
c55b51a0 | 360 | hrtimer_start(&it.timer, ns_to_ktime(duration_ns), |
98484179 | 361 | HRTIMER_MODE_REL_PINNED_HARD); |
c1de45ca PZ |
362 | |
363 | while (!READ_ONCE(it.done)) | |
364 | do_idle(); | |
365 | ||
c55b51a0 | 366 | cpuidle_use_deepest_state(0); |
c1de45ca PZ |
367 | current->flags &= ~PF_IDLE; |
368 | ||
369 | preempt_fold_need_resched(); | |
370 | preempt_enable(); | |
371 | } | |
c55b51a0 | 372 | EXPORT_SYMBOL_GPL(play_idle_precise); |
c1de45ca | 373 | |
cf37b6b4 NP |
374 | void cpu_startup_entry(enum cpuhp_state state) |
375 | { | |
cf37b6b4 | 376 | arch_cpu_idle_prepare(); |
8df3e07e | 377 | cpuhp_online_idle(state); |
c1de45ca PZ |
378 | while (1) |
379 | do_idle(); | |
cf37b6b4 | 380 | } |
a92057e1 IM |
381 | |
382 | /* | |
383 | * idle-task scheduling class. | |
384 | */ | |
385 | ||
386 | #ifdef CONFIG_SMP | |
387 | static int | |
3aef1551 | 388 | select_task_rq_idle(struct task_struct *p, int cpu, int flags) |
a92057e1 IM |
389 | { |
390 | return task_cpu(p); /* IDLE tasks as never migrated */ | |
391 | } | |
6e2df058 PZ |
392 | |
393 | static int | |
394 | balance_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) | |
395 | { | |
396 | return WARN_ON_ONCE(1); | |
397 | } | |
a92057e1 IM |
398 | #endif |
399 | ||
400 | /* | |
401 | * Idle tasks are unconditionally rescheduled: | |
402 | */ | |
e23edc86 | 403 | static void wakeup_preempt_idle(struct rq *rq, struct task_struct *p, int flags) |
a92057e1 IM |
404 | { |
405 | resched_curr(rq); | |
406 | } | |
407 | ||
6e2df058 | 408 | static void put_prev_task_idle(struct rq *rq, struct task_struct *prev) |
03b7fad1 PZ |
409 | { |
410 | } | |
411 | ||
a0e813f2 | 412 | static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool first) |
a92057e1 | 413 | { |
a92057e1 IM |
414 | update_idle_core(rq); |
415 | schedstat_inc(rq->sched_goidle); | |
03b7fad1 PZ |
416 | } |
417 | ||
21f56ffe PZ |
418 | #ifdef CONFIG_SMP |
419 | static struct task_struct *pick_task_idle(struct rq *rq) | |
420 | { | |
421 | return rq->idle; | |
422 | } | |
423 | #endif | |
424 | ||
98c2f700 | 425 | struct task_struct *pick_next_task_idle(struct rq *rq) |
a92057e1 | 426 | { |
03b7fad1 PZ |
427 | struct task_struct *next = rq->idle; |
428 | ||
a0e813f2 | 429 | set_next_task_idle(rq, next, true); |
a92057e1 | 430 | |
03b7fad1 | 431 | return next; |
a92057e1 IM |
432 | } |
433 | ||
434 | /* | |
435 | * It is not legal to sleep in the idle task - print a warning | |
436 | * message if some code attempts to do it: | |
437 | */ | |
438 | static void | |
439 | dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags) | |
440 | { | |
5cb9eaa3 | 441 | raw_spin_rq_unlock_irq(rq); |
a92057e1 IM |
442 | printk(KERN_ERR "bad: scheduling from the idle thread!\n"); |
443 | dump_stack(); | |
5cb9eaa3 | 444 | raw_spin_rq_lock_irq(rq); |
a92057e1 IM |
445 | } |
446 | ||
a92057e1 IM |
447 | /* |
448 | * scheduler tick hitting a task of our scheduling class. | |
449 | * | |
450 | * NOTE: This function can be called remotely by the tick offload that | |
451 | * goes along full dynticks. Therefore no local assumption can be made | |
452 | * and everything must be accessed through the @rq and @curr passed in | |
453 | * parameters. | |
454 | */ | |
455 | static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued) | |
456 | { | |
457 | } | |
458 | ||
a92057e1 IM |
459 | static void switched_to_idle(struct rq *rq, struct task_struct *p) |
460 | { | |
461 | BUG(); | |
462 | } | |
463 | ||
464 | static void | |
465 | prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio) | |
466 | { | |
467 | BUG(); | |
468 | } | |
469 | ||
a92057e1 IM |
470 | static void update_curr_idle(struct rq *rq) |
471 | { | |
472 | } | |
473 | ||
474 | /* | |
475 | * Simple, special scheduling class for the per-CPU idle tasks: | |
476 | */ | |
43c31ac0 PZ |
477 | DEFINE_SCHED_CLASS(idle) = { |
478 | ||
a92057e1 IM |
479 | /* no enqueue/yield_task for idle tasks */ |
480 | ||
481 | /* dequeue is not valid, we print a debug message there: */ | |
482 | .dequeue_task = dequeue_task_idle, | |
483 | ||
e23edc86 | 484 | .wakeup_preempt = wakeup_preempt_idle, |
a92057e1 IM |
485 | |
486 | .pick_next_task = pick_next_task_idle, | |
487 | .put_prev_task = put_prev_task_idle, | |
03b7fad1 | 488 | .set_next_task = set_next_task_idle, |
a92057e1 IM |
489 | |
490 | #ifdef CONFIG_SMP | |
6e2df058 | 491 | .balance = balance_idle, |
21f56ffe | 492 | .pick_task = pick_task_idle, |
a92057e1 IM |
493 | .select_task_rq = select_task_rq_idle, |
494 | .set_cpus_allowed = set_cpus_allowed_common, | |
495 | #endif | |
496 | ||
a92057e1 IM |
497 | .task_tick = task_tick_idle, |
498 | ||
a92057e1 IM |
499 | .prio_changed = prio_changed_idle, |
500 | .switched_to = switched_to_idle, | |
501 | .update_curr = update_curr_idle, | |
502 | }; |