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/cpuhotplug.h>
  8#include <linux/tick.h>
  9#include <linux/mm.h>
 10#include <linux/stackprotector.h>
 11#include <linux/suspend.h>
 12
 13#include <asm/tlb.h>
 14
 15#include <trace/events/power.h>
 16
 17#include "sched.h"
 18
 19/* Linker adds these: start and end of __cpuidle functions */
 20extern char __cpuidle_text_start[], __cpuidle_text_end[];
 21
 22/**
 23 * sched_idle_set_state - Record idle state for the current CPU.
 24 * @idle_state: State to record.
 25 */
 26void sched_idle_set_state(struct cpuidle_state *idle_state)
 27{
 28	idle_set_state(this_rq(), idle_state);
 29}
 30
 31static int __read_mostly cpu_idle_force_poll;
 32
 33void cpu_idle_poll_ctrl(bool enable)
 34{
 35	if (enable) {
 36		cpu_idle_force_poll++;
 37	} else {
 38		cpu_idle_force_poll--;
 39		WARN_ON_ONCE(cpu_idle_force_poll < 0);
 40	}
 41}
 42
 43#ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
 44static int __init cpu_idle_poll_setup(char *__unused)
 45{
 46	cpu_idle_force_poll = 1;
 47	return 1;
 48}
 49__setup("nohlt", cpu_idle_poll_setup);
 50
 51static int __init cpu_idle_nopoll_setup(char *__unused)
 52{
 53	cpu_idle_force_poll = 0;
 54	return 1;
 55}
 56__setup("hlt", cpu_idle_nopoll_setup);
 57#endif
 58
 59static noinline int __cpuidle cpu_idle_poll(void)
 60{
 61	rcu_idle_enter();
 62	trace_cpu_idle_rcuidle(0, smp_processor_id());
 63	local_irq_enable();
 64	stop_critical_timings();
 65	while (!tif_need_resched() &&
 66		(cpu_idle_force_poll || tick_check_broadcast_expired()))
 67		cpu_relax();
 68	start_critical_timings();
 69	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
 70	rcu_idle_exit();
 71	return 1;
 72}
 73
 74/* Weak implementations for optional arch specific functions */
 75void __weak arch_cpu_idle_prepare(void) { }
 76void __weak arch_cpu_idle_enter(void) { }
 77void __weak arch_cpu_idle_exit(void) { }
 78void __weak arch_cpu_idle_dead(void) { }
 79void __weak arch_cpu_idle(void)
 80{
 81	cpu_idle_force_poll = 1;
 82	local_irq_enable();
 83}
 84
 85/**
 86 * default_idle_call - Default CPU idle routine.
 87 *
 88 * To use when the cpuidle framework cannot be used.
 89 */
 90void __cpuidle default_idle_call(void)
 91{
 92	if (current_clr_polling_and_test()) {
 93		local_irq_enable();
 94	} else {
 95		stop_critical_timings();
 96		arch_cpu_idle();
 97		start_critical_timings();
 98	}
 99}
100
101static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
102		      int next_state)
103{
104	/*
105	 * The idle task must be scheduled, it is pointless to go to idle, just
106	 * update no idle residency and return.
107	 */
108	if (current_clr_polling_and_test()) {
109		dev->last_residency = 0;
110		local_irq_enable();
111		return -EBUSY;
112	}
113
114	/*
115	 * Enter the idle state previously returned by the governor decision.
116	 * This function will block until an interrupt occurs and will take
117	 * care of re-enabling the local interrupts
118	 */
119	return cpuidle_enter(drv, dev, next_state);
120}
121
122/**
123 * cpuidle_idle_call - the main idle function
124 *
125 * NOTE: no locks or semaphores should be used here
126 *
127 * On archs that support TIF_POLLING_NRFLAG, is called with polling
128 * set, and it returns with polling set.  If it ever stops polling, it
129 * must clear the polling bit.
130 */
131static void cpuidle_idle_call(void)
132{
133	struct cpuidle_device *dev = cpuidle_get_device();
134	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
135	int next_state, entered_state;
136
137	/*
138	 * Check if the idle task must be rescheduled. If it is the
139	 * case, exit the function after re-enabling the local irq.
140	 */
141	if (need_resched()) {
142		local_irq_enable();
143		return;
144	}
145
146	/*
147	 * Tell the RCU framework we are entering an idle section,
148	 * so no more rcu read side critical sections and one more
149	 * step to the grace period
150	 */
151	rcu_idle_enter();
152
153	if (cpuidle_not_available(drv, dev)) {
154		default_idle_call();
155		goto exit_idle;
156	}
157
158	/*
159	 * Suspend-to-idle ("freeze") is a system state in which all user space
160	 * has been frozen, all I/O devices have been suspended and the only
161	 * activity happens here and in iterrupts (if any).  In that case bypass
162	 * the cpuidle governor and go stratight for the deepest idle state
163	 * available.  Possibly also suspend the local tick and the entire
164	 * timekeeping to prevent timer interrupts from kicking us out of idle
165	 * until a proper wakeup interrupt happens.
166	 */
167
168	if (idle_should_freeze() || dev->use_deepest_state) {
169		if (idle_should_freeze()) {
170			entered_state = cpuidle_enter_freeze(drv, dev);
171			if (entered_state > 0) {
172				local_irq_enable();
173				goto exit_idle;
174			}
175		}
176
177		next_state = cpuidle_find_deepest_state(drv, dev);
178		call_cpuidle(drv, dev, next_state);
179	} else {
180		/*
181		 * Ask the cpuidle framework to choose a convenient idle state.
182		 */
183		next_state = cpuidle_select(drv, dev);
184		entered_state = call_cpuidle(drv, dev, next_state);
185		/*
186		 * Give the governor an opportunity to reflect on the outcome
187		 */
188		cpuidle_reflect(dev, entered_state);
189	}
190
191exit_idle:
192	__current_set_polling();
193
194	/*
195	 * It is up to the idle functions to reenable local interrupts
196	 */
197	if (WARN_ON_ONCE(irqs_disabled()))
198		local_irq_enable();
199
200	rcu_idle_exit();
201}
202
203/*
204 * Generic idle loop implementation
205 *
206 * Called with polling cleared.
207 */
208static void do_idle(void)
209{
210	/*
211	 * If the arch has a polling bit, we maintain an invariant:
212	 *
213	 * Our polling bit is clear if we're not scheduled (i.e. if rq->curr !=
214	 * rq->idle). This means that, if rq->idle has the polling bit set,
215	 * then setting need_resched is guaranteed to cause the CPU to
216	 * reschedule.
217	 */
218
219	__current_set_polling();
220	tick_nohz_idle_enter();
221
222	while (!need_resched()) {
223		check_pgt_cache();
224		rmb();
225
226		if (cpu_is_offline(smp_processor_id())) {
227			cpuhp_report_idle_dead();
228			arch_cpu_idle_dead();
229		}
230
231		local_irq_disable();
232		arch_cpu_idle_enter();
233
234		/*
235		 * In poll mode we reenable interrupts and spin. Also if we
236		 * detected in the wakeup from idle path that the tick
237		 * broadcast device expired for us, we don't want to go deep
238		 * idle as we know that the IPI is going to arrive right away.
239		 */
240		if (cpu_idle_force_poll || tick_check_broadcast_expired())
241			cpu_idle_poll();
242		else
243			cpuidle_idle_call();
244		arch_cpu_idle_exit();
245	}
246
247	/*
248	 * Since we fell out of the loop above, we know TIF_NEED_RESCHED must
249	 * be set, propagate it into PREEMPT_NEED_RESCHED.
250	 *
251	 * This is required because for polling idle loops we will not have had
252	 * an IPI to fold the state for us.
253	 */
254	preempt_set_need_resched();
255	tick_nohz_idle_exit();
256	__current_clr_polling();
257
258	/*
259	 * We promise to call sched_ttwu_pending() and reschedule if
260	 * need_resched() is set while polling is set. That means that clearing
261	 * polling needs to be visible before doing these things.
262	 */
263	smp_mb__after_atomic();
264
265	sched_ttwu_pending();
266	schedule_preempt_disabled();
267}
268
269bool cpu_in_idle(unsigned long pc)
270{
271	return pc >= (unsigned long)__cpuidle_text_start &&
272		pc < (unsigned long)__cpuidle_text_end;
273}
274
275struct idle_timer {
276	struct hrtimer timer;
277	int done;
278};
279
280static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer)
281{
282	struct idle_timer *it = container_of(timer, struct idle_timer, timer);
283
284	WRITE_ONCE(it->done, 1);
285	set_tsk_need_resched(current);
286
287	return HRTIMER_NORESTART;
288}
289
290void play_idle(unsigned long duration_ms)
291{
292	struct idle_timer it;
293
294	/*
295	 * Only FIFO tasks can disable the tick since they don't need the forced
296	 * preemption.
297	 */
298	WARN_ON_ONCE(current->policy != SCHED_FIFO);
299	WARN_ON_ONCE(current->nr_cpus_allowed != 1);
300	WARN_ON_ONCE(!(current->flags & PF_KTHREAD));
301	WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY));
302	WARN_ON_ONCE(!duration_ms);
303
304	rcu_sleep_check();
305	preempt_disable();
306	current->flags |= PF_IDLE;
307	cpuidle_use_deepest_state(true);
308
309	it.done = 0;
310	hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
311	it.timer.function = idle_inject_timer_fn;
312	hrtimer_start(&it.timer, ms_to_ktime(duration_ms), HRTIMER_MODE_REL_PINNED);
313
314	while (!READ_ONCE(it.done))
315		do_idle();
316
317	cpuidle_use_deepest_state(false);
318	current->flags &= ~PF_IDLE;
319
320	preempt_fold_need_resched();
321	preempt_enable();
322}
323EXPORT_SYMBOL_GPL(play_idle);
324
325void cpu_startup_entry(enum cpuhp_state state)
326{
327	/*
328	 * This #ifdef needs to die, but it's too late in the cycle to
329	 * make this generic (arm and sh have never invoked the canary
330	 * init for the non boot cpus!). Will be fixed in 3.11
331	 */
332#ifdef CONFIG_X86
333	/*
334	 * If we're the non-boot CPU, nothing set the stack canary up
335	 * for us. The boot CPU already has it initialized but no harm
336	 * in doing it again. This is a good place for updating it, as
337	 * we wont ever return from this function (so the invalid
338	 * canaries already on the stack wont ever trigger).
339	 */
340	boot_init_stack_canary();
341#endif
342	arch_cpu_idle_prepare();
343	cpuhp_online_idle(state);
344	while (1)
345		do_idle();
346}