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1/*
2 * Generic entry point for the idle threads
3 */
4#include <linux/sched.h>
5#include <linux/cpu.h>
6#include <linux/cpuidle.h>
7#include <linux/tick.h>
8#include <linux/mm.h>
9#include <linux/stackprotector.h>
10
11#include <asm/tlb.h>
12
13#include <trace/events/power.h>
14
15static int __read_mostly cpu_idle_force_poll;
16
17void cpu_idle_poll_ctrl(bool enable)
18{
19 if (enable) {
20 cpu_idle_force_poll++;
21 } else {
22 cpu_idle_force_poll--;
23 WARN_ON_ONCE(cpu_idle_force_poll < 0);
24 }
25}
26
27#ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
28static int __init cpu_idle_poll_setup(char *__unused)
29{
30 cpu_idle_force_poll = 1;
31 return 1;
32}
33__setup("nohlt", cpu_idle_poll_setup);
34
35static int __init cpu_idle_nopoll_setup(char *__unused)
36{
37 cpu_idle_force_poll = 0;
38 return 1;
39}
40__setup("hlt", cpu_idle_nopoll_setup);
41#endif
42
43static inline int cpu_idle_poll(void)
44{
45 rcu_idle_enter();
46 trace_cpu_idle_rcuidle(0, smp_processor_id());
47 local_irq_enable();
48 while (!tif_need_resched())
49 cpu_relax();
50 trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
51 rcu_idle_exit();
52 return 1;
53}
54
55/* Weak implementations for optional arch specific functions */
56void __weak arch_cpu_idle_prepare(void) { }
57void __weak arch_cpu_idle_enter(void) { }
58void __weak arch_cpu_idle_exit(void) { }
59void __weak arch_cpu_idle_dead(void) { }
60void __weak arch_cpu_idle(void)
61{
62 cpu_idle_force_poll = 1;
63 local_irq_enable();
64}
65
66/**
67 * cpuidle_idle_call - the main idle function
68 *
69 * NOTE: no locks or semaphores should be used here
70 * return non-zero on failure
71 */
72static int cpuidle_idle_call(void)
73{
74 struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
75 struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
76 int next_state, entered_state, ret;
77 bool broadcast;
78
79 /*
80 * Check if the idle task must be rescheduled. If it is the
81 * case, exit the function after re-enabling the local irq and
82 * set again the polling flag
83 */
84 if (current_clr_polling_and_test()) {
85 local_irq_enable();
86 __current_set_polling();
87 return 0;
88 }
89
90 /*
91 * During the idle period, stop measuring the disabled irqs
92 * critical sections latencies
93 */
94 stop_critical_timings();
95
96 /*
97 * Tell the RCU framework we are entering an idle section,
98 * so no more rcu read side critical sections and one more
99 * step to the grace period
100 */
101 rcu_idle_enter();
102
103 /*
104 * Check if the cpuidle framework is ready, otherwise fallback
105 * to the default arch specific idle method
106 */
107 ret = cpuidle_enabled(drv, dev);
108
109 if (!ret) {
110 /*
111 * Ask the governor to choose an idle state it thinks
112 * it is convenient to go to. There is *always* a
113 * convenient idle state
114 */
115 next_state = cpuidle_select(drv, dev);
116
117 /*
118 * The idle task must be scheduled, it is pointless to
119 * go to idle, just update no idle residency and get
120 * out of this function
121 */
122 if (current_clr_polling_and_test()) {
123 dev->last_residency = 0;
124 entered_state = next_state;
125 local_irq_enable();
126 } else {
127 broadcast = !!(drv->states[next_state].flags &
128 CPUIDLE_FLAG_TIMER_STOP);
129
130 if (broadcast)
131 /*
132 * Tell the time framework to switch
133 * to a broadcast timer because our
134 * local timer will be shutdown. If a
135 * local timer is used from another
136 * cpu as a broadcast timer, this call
137 * may fail if it is not available
138 */
139 ret = clockevents_notify(
140 CLOCK_EVT_NOTIFY_BROADCAST_ENTER,
141 &dev->cpu);
142
143 if (!ret) {
144 trace_cpu_idle_rcuidle(next_state, dev->cpu);
145
146 /*
147 * Enter the idle state previously
148 * returned by the governor
149 * decision. This function will block
150 * until an interrupt occurs and will
151 * take care of re-enabling the local
152 * interrupts
153 */
154 entered_state = cpuidle_enter(drv, dev,
155 next_state);
156
157 trace_cpu_idle_rcuidle(PWR_EVENT_EXIT,
158 dev->cpu);
159
160 if (broadcast)
161 clockevents_notify(
162 CLOCK_EVT_NOTIFY_BROADCAST_EXIT,
163 &dev->cpu);
164
165 /*
166 * Give the governor an opportunity to reflect on the
167 * outcome
168 */
169 cpuidle_reflect(dev, entered_state);
170 }
171 }
172 }
173
174 /*
175 * We can't use the cpuidle framework, let's use the default
176 * idle routine
177 */
178 if (ret)
179 arch_cpu_idle();
180
181 __current_set_polling();
182
183 /*
184 * It is up to the idle functions to enable back the local
185 * interrupt
186 */
187 if (WARN_ON_ONCE(irqs_disabled()))
188 local_irq_enable();
189
190 rcu_idle_exit();
191 start_critical_timings();
192
193 return 0;
194}
195
196/*
197 * Generic idle loop implementation
198 */
199static void cpu_idle_loop(void)
200{
201 while (1) {
202 tick_nohz_idle_enter();
203
204 while (!need_resched()) {
205 check_pgt_cache();
206 rmb();
207
208 if (cpu_is_offline(smp_processor_id()))
209 arch_cpu_idle_dead();
210
211 local_irq_disable();
212 arch_cpu_idle_enter();
213
214 /*
215 * In poll mode we reenable interrupts and spin.
216 *
217 * Also if we detected in the wakeup from idle
218 * path that the tick broadcast device expired
219 * for us, we don't want to go deep idle as we
220 * know that the IPI is going to arrive right
221 * away
222 */
223 if (cpu_idle_force_poll || tick_check_broadcast_expired())
224 cpu_idle_poll();
225 else
226 cpuidle_idle_call();
227
228 arch_cpu_idle_exit();
229 }
230
231 /*
232 * Since we fell out of the loop above, we know
233 * TIF_NEED_RESCHED must be set, propagate it into
234 * PREEMPT_NEED_RESCHED.
235 *
236 * This is required because for polling idle loops we will
237 * not have had an IPI to fold the state for us.
238 */
239 preempt_set_need_resched();
240 tick_nohz_idle_exit();
241 schedule_preempt_disabled();
242 }
243}
244
245void cpu_startup_entry(enum cpuhp_state state)
246{
247 /*
248 * This #ifdef needs to die, but it's too late in the cycle to
249 * make this generic (arm and sh have never invoked the canary
250 * init for the non boot cpus!). Will be fixed in 3.11
251 */
252#ifdef CONFIG_X86
253 /*
254 * If we're the non-boot CPU, nothing set the stack canary up
255 * for us. The boot CPU already has it initialized but no harm
256 * in doing it again. This is a good place for updating it, as
257 * we wont ever return from this function (so the invalid
258 * canaries already on the stack wont ever trigger).
259 */
260 boot_init_stack_canary();
261#endif
262 __current_set_polling();
263 arch_cpu_idle_prepare();
264 cpu_idle_loop();
265}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
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 )
8 */
9#include "sched.h"
10
11#include <trace/events/power.h>
12
13/* Linker adds these: start and end of __cpuidle functions */
14extern char __cpuidle_text_start[], __cpuidle_text_end[];
15
16/**
17 * sched_idle_set_state - Record idle state for the current CPU.
18 * @idle_state: State to record.
19 */
20void sched_idle_set_state(struct cpuidle_state *idle_state)
21{
22 idle_set_state(this_rq(), idle_state);
23}
24
25static int __read_mostly cpu_idle_force_poll;
26
27void 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
38static int __init cpu_idle_poll_setup(char *__unused)
39{
40 cpu_idle_force_poll = 1;
41
42 return 1;
43}
44__setup("nohlt", cpu_idle_poll_setup);
45
46static int __init cpu_idle_nopoll_setup(char *__unused)
47{
48 cpu_idle_force_poll = 0;
49
50 return 1;
51}
52__setup("hlt", cpu_idle_nopoll_setup);
53#endif
54
55static noinline int __cpuidle cpu_idle_poll(void)
56{
57 trace_cpu_idle(0, smp_processor_id());
58 stop_critical_timings();
59 rcu_idle_enter();
60 local_irq_enable();
61
62 while (!tif_need_resched() &&
63 (cpu_idle_force_poll || tick_check_broadcast_expired()))
64 cpu_relax();
65
66 rcu_idle_exit();
67 start_critical_timings();
68 trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
69
70 return 1;
71}
72
73/* Weak implementations for optional arch specific functions */
74void __weak arch_cpu_idle_prepare(void) { }
75void __weak arch_cpu_idle_enter(void) { }
76void __weak arch_cpu_idle_exit(void) { }
77void __weak arch_cpu_idle_dead(void) { }
78void __weak arch_cpu_idle(void)
79{
80 cpu_idle_force_poll = 1;
81 raw_local_irq_enable();
82}
83
84/**
85 * default_idle_call - Default CPU idle routine.
86 *
87 * To use when the cpuidle framework cannot be used.
88 */
89void __cpuidle default_idle_call(void)
90{
91 if (current_clr_polling_and_test()) {
92 local_irq_enable();
93 } else {
94
95 trace_cpu_idle(1, smp_processor_id());
96 stop_critical_timings();
97
98 /*
99 * arch_cpu_idle() is supposed to enable IRQs, however
100 * we can't do that because of RCU and tracing.
101 *
102 * Trace IRQs enable here, then switch off RCU, and have
103 * arch_cpu_idle() use raw_local_irq_enable(). Note that
104 * rcu_idle_enter() relies on lockdep IRQ state, so switch that
105 * last -- this is very similar to the entry code.
106 */
107 trace_hardirqs_on_prepare();
108 lockdep_hardirqs_on_prepare(_THIS_IP_);
109 rcu_idle_enter();
110 lockdep_hardirqs_on(_THIS_IP_);
111
112 arch_cpu_idle();
113
114 /*
115 * OK, so IRQs are enabled here, but RCU needs them disabled to
116 * turn itself back on.. funny thing is that disabling IRQs
117 * will cause tracing, which needs RCU. Jump through hoops to
118 * make it 'work'.
119 */
120 raw_local_irq_disable();
121 lockdep_hardirqs_off(_THIS_IP_);
122 rcu_idle_exit();
123 lockdep_hardirqs_on(_THIS_IP_);
124 raw_local_irq_enable();
125
126 start_critical_timings();
127 trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
128 }
129}
130
131static int call_cpuidle_s2idle(struct cpuidle_driver *drv,
132 struct cpuidle_device *dev)
133{
134 if (current_clr_polling_and_test())
135 return -EBUSY;
136
137 return cpuidle_enter_s2idle(drv, dev);
138}
139
140static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
141 int next_state)
142{
143 /*
144 * The idle task must be scheduled, it is pointless to go to idle, just
145 * update no idle residency and return.
146 */
147 if (current_clr_polling_and_test()) {
148 dev->last_residency_ns = 0;
149 local_irq_enable();
150 return -EBUSY;
151 }
152
153 /*
154 * Enter the idle state previously returned by the governor decision.
155 * This function will block until an interrupt occurs and will take
156 * care of re-enabling the local interrupts
157 */
158 return cpuidle_enter(drv, dev, next_state);
159}
160
161/**
162 * cpuidle_idle_call - the main idle function
163 *
164 * NOTE: no locks or semaphores should be used here
165 *
166 * On architectures that support TIF_POLLING_NRFLAG, is called with polling
167 * set, and it returns with polling set. If it ever stops polling, it
168 * must clear the polling bit.
169 */
170static void cpuidle_idle_call(void)
171{
172 struct cpuidle_device *dev = cpuidle_get_device();
173 struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
174 int next_state, entered_state;
175
176 /*
177 * Check if the idle task must be rescheduled. If it is the
178 * case, exit the function after re-enabling the local irq.
179 */
180 if (need_resched()) {
181 local_irq_enable();
182 return;
183 }
184
185 /*
186 * The RCU framework needs to be told that we are entering an idle
187 * section, so no more rcu read side critical sections and one more
188 * step to the grace period
189 */
190
191 if (cpuidle_not_available(drv, dev)) {
192 tick_nohz_idle_stop_tick();
193
194 default_idle_call();
195 goto exit_idle;
196 }
197
198 /*
199 * Suspend-to-idle ("s2idle") is a system state in which all user space
200 * has been frozen, all I/O devices have been suspended and the only
201 * activity happens here and in interrupts (if any). In that case bypass
202 * the cpuidle governor and go straight for the deepest idle state
203 * available. Possibly also suspend the local tick and the entire
204 * timekeeping to prevent timer interrupts from kicking us out of idle
205 * until a proper wakeup interrupt happens.
206 */
207
208 if (idle_should_enter_s2idle() || dev->forced_idle_latency_limit_ns) {
209 u64 max_latency_ns;
210
211 if (idle_should_enter_s2idle()) {
212
213 entered_state = call_cpuidle_s2idle(drv, dev);
214 if (entered_state > 0)
215 goto exit_idle;
216
217 max_latency_ns = U64_MAX;
218 } else {
219 max_latency_ns = dev->forced_idle_latency_limit_ns;
220 }
221
222 tick_nohz_idle_stop_tick();
223
224 next_state = cpuidle_find_deepest_state(drv, dev, max_latency_ns);
225 call_cpuidle(drv, dev, next_state);
226 } else {
227 bool stop_tick = true;
228
229 /*
230 * Ask the cpuidle framework to choose a convenient idle state.
231 */
232 next_state = cpuidle_select(drv, dev, &stop_tick);
233
234 if (stop_tick || tick_nohz_tick_stopped())
235 tick_nohz_idle_stop_tick();
236 else
237 tick_nohz_idle_retain_tick();
238
239 entered_state = call_cpuidle(drv, dev, next_state);
240 /*
241 * Give the governor an opportunity to reflect on the outcome
242 */
243 cpuidle_reflect(dev, entered_state);
244 }
245
246exit_idle:
247 __current_set_polling();
248
249 /*
250 * It is up to the idle functions to reenable local interrupts
251 */
252 if (WARN_ON_ONCE(irqs_disabled()))
253 local_irq_enable();
254}
255
256/*
257 * Generic idle loop implementation
258 *
259 * Called with polling cleared.
260 */
261static void do_idle(void)
262{
263 int cpu = smp_processor_id();
264
265 /*
266 * Check if we need to update blocked load
267 */
268 nohz_run_idle_balance(cpu);
269
270 /*
271 * If the arch has a polling bit, we maintain an invariant:
272 *
273 * Our polling bit is clear if we're not scheduled (i.e. if rq->curr !=
274 * rq->idle). This means that, if rq->idle has the polling bit set,
275 * then setting need_resched is guaranteed to cause the CPU to
276 * reschedule.
277 */
278
279 __current_set_polling();
280 tick_nohz_idle_enter();
281
282 while (!need_resched()) {
283 rmb();
284
285 local_irq_disable();
286
287 if (cpu_is_offline(cpu)) {
288 tick_nohz_idle_stop_tick();
289 cpuhp_report_idle_dead();
290 arch_cpu_idle_dead();
291 }
292
293 arch_cpu_idle_enter();
294 rcu_nocb_flush_deferred_wakeup();
295
296 /*
297 * In poll mode we reenable interrupts and spin. Also if we
298 * detected in the wakeup from idle path that the tick
299 * broadcast device expired for us, we don't want to go deep
300 * idle as we know that the IPI is going to arrive right away.
301 */
302 if (cpu_idle_force_poll || tick_check_broadcast_expired()) {
303 tick_nohz_idle_restart_tick();
304 cpu_idle_poll();
305 } else {
306 cpuidle_idle_call();
307 }
308 arch_cpu_idle_exit();
309 }
310
311 /*
312 * Since we fell out of the loop above, we know TIF_NEED_RESCHED must
313 * be set, propagate it into PREEMPT_NEED_RESCHED.
314 *
315 * This is required because for polling idle loops we will not have had
316 * an IPI to fold the state for us.
317 */
318 preempt_set_need_resched();
319 tick_nohz_idle_exit();
320 __current_clr_polling();
321
322 /*
323 * We promise to call sched_ttwu_pending() and reschedule if
324 * need_resched() is set while polling is set. That means that clearing
325 * polling needs to be visible before doing these things.
326 */
327 smp_mb__after_atomic();
328
329 /*
330 * RCU relies on this call to be done outside of an RCU read-side
331 * critical section.
332 */
333 flush_smp_call_function_from_idle();
334 schedule_idle();
335
336 if (unlikely(klp_patch_pending(current)))
337 klp_update_patch_state(current);
338}
339
340bool cpu_in_idle(unsigned long pc)
341{
342 return pc >= (unsigned long)__cpuidle_text_start &&
343 pc < (unsigned long)__cpuidle_text_end;
344}
345
346struct idle_timer {
347 struct hrtimer timer;
348 int done;
349};
350
351static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer)
352{
353 struct idle_timer *it = container_of(timer, struct idle_timer, timer);
354
355 WRITE_ONCE(it->done, 1);
356 set_tsk_need_resched(current);
357
358 return HRTIMER_NORESTART;
359}
360
361void play_idle_precise(u64 duration_ns, u64 latency_ns)
362{
363 struct idle_timer it;
364
365 /*
366 * Only FIFO tasks can disable the tick since they don't need the forced
367 * preemption.
368 */
369 WARN_ON_ONCE(current->policy != SCHED_FIFO);
370 WARN_ON_ONCE(current->nr_cpus_allowed != 1);
371 WARN_ON_ONCE(!(current->flags & PF_KTHREAD));
372 WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY));
373 WARN_ON_ONCE(!duration_ns);
374 WARN_ON_ONCE(current->mm);
375
376 rcu_sleep_check();
377 preempt_disable();
378 current->flags |= PF_IDLE;
379 cpuidle_use_deepest_state(latency_ns);
380
381 it.done = 0;
382 hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
383 it.timer.function = idle_inject_timer_fn;
384 hrtimer_start(&it.timer, ns_to_ktime(duration_ns),
385 HRTIMER_MODE_REL_PINNED_HARD);
386
387 while (!READ_ONCE(it.done))
388 do_idle();
389
390 cpuidle_use_deepest_state(0);
391 current->flags &= ~PF_IDLE;
392
393 preempt_fold_need_resched();
394 preempt_enable();
395}
396EXPORT_SYMBOL_GPL(play_idle_precise);
397
398void cpu_startup_entry(enum cpuhp_state state)
399{
400 arch_cpu_idle_prepare();
401 cpuhp_online_idle(state);
402 while (1)
403 do_idle();
404}
405
406/*
407 * idle-task scheduling class.
408 */
409
410#ifdef CONFIG_SMP
411static int
412select_task_rq_idle(struct task_struct *p, int cpu, int flags)
413{
414 return task_cpu(p); /* IDLE tasks as never migrated */
415}
416
417static int
418balance_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
419{
420 return WARN_ON_ONCE(1);
421}
422#endif
423
424/*
425 * Idle tasks are unconditionally rescheduled:
426 */
427static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
428{
429 resched_curr(rq);
430}
431
432static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
433{
434}
435
436static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool first)
437{
438 update_idle_core(rq);
439 schedstat_inc(rq->sched_goidle);
440 queue_core_balance(rq);
441}
442
443#ifdef CONFIG_SMP
444static struct task_struct *pick_task_idle(struct rq *rq)
445{
446 return rq->idle;
447}
448#endif
449
450struct task_struct *pick_next_task_idle(struct rq *rq)
451{
452 struct task_struct *next = rq->idle;
453
454 set_next_task_idle(rq, next, true);
455
456 return next;
457}
458
459/*
460 * It is not legal to sleep in the idle task - print a warning
461 * message if some code attempts to do it:
462 */
463static void
464dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
465{
466 raw_spin_rq_unlock_irq(rq);
467 printk(KERN_ERR "bad: scheduling from the idle thread!\n");
468 dump_stack();
469 raw_spin_rq_lock_irq(rq);
470}
471
472/*
473 * scheduler tick hitting a task of our scheduling class.
474 *
475 * NOTE: This function can be called remotely by the tick offload that
476 * goes along full dynticks. Therefore no local assumption can be made
477 * and everything must be accessed through the @rq and @curr passed in
478 * parameters.
479 */
480static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
481{
482}
483
484static void switched_to_idle(struct rq *rq, struct task_struct *p)
485{
486 BUG();
487}
488
489static void
490prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
491{
492 BUG();
493}
494
495static void update_curr_idle(struct rq *rq)
496{
497}
498
499/*
500 * Simple, special scheduling class for the per-CPU idle tasks:
501 */
502DEFINE_SCHED_CLASS(idle) = {
503
504 /* no enqueue/yield_task for idle tasks */
505
506 /* dequeue is not valid, we print a debug message there: */
507 .dequeue_task = dequeue_task_idle,
508
509 .check_preempt_curr = check_preempt_curr_idle,
510
511 .pick_next_task = pick_next_task_idle,
512 .put_prev_task = put_prev_task_idle,
513 .set_next_task = set_next_task_idle,
514
515#ifdef CONFIG_SMP
516 .balance = balance_idle,
517 .pick_task = pick_task_idle,
518 .select_task_rq = select_task_rq_idle,
519 .set_cpus_allowed = set_cpus_allowed_common,
520#endif
521
522 .task_tick = task_tick_idle,
523
524 .prio_changed = prio_changed_idle,
525 .switched_to = switched_to_idle,
526 .update_curr = update_curr_idle,
527};