Commit | Line | Data |
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cf37b6b4 NP |
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> | |
38106313 | 10 | #include <linux/suspend.h> |
cf37b6b4 NP |
11 | |
12 | #include <asm/tlb.h> | |
13 | ||
14 | #include <trace/events/power.h> | |
15 | ||
e3baac47 PZ |
16 | #include "sched.h" |
17 | ||
cf37b6b4 NP |
18 | static int __read_mostly cpu_idle_force_poll; |
19 | ||
20 | void cpu_idle_poll_ctrl(bool enable) | |
21 | { | |
22 | if (enable) { | |
23 | cpu_idle_force_poll++; | |
24 | } else { | |
25 | cpu_idle_force_poll--; | |
26 | WARN_ON_ONCE(cpu_idle_force_poll < 0); | |
27 | } | |
28 | } | |
29 | ||
30 | #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP | |
31 | static int __init cpu_idle_poll_setup(char *__unused) | |
32 | { | |
33 | cpu_idle_force_poll = 1; | |
34 | return 1; | |
35 | } | |
36 | __setup("nohlt", cpu_idle_poll_setup); | |
37 | ||
38 | static int __init cpu_idle_nopoll_setup(char *__unused) | |
39 | { | |
40 | cpu_idle_force_poll = 0; | |
41 | return 1; | |
42 | } | |
43 | __setup("hlt", cpu_idle_nopoll_setup); | |
44 | #endif | |
45 | ||
46 | static inline int cpu_idle_poll(void) | |
47 | { | |
48 | rcu_idle_enter(); | |
49 | trace_cpu_idle_rcuidle(0, smp_processor_id()); | |
50 | local_irq_enable(); | |
ff6f2d29 PM |
51 | while (!tif_need_resched() && |
52 | (cpu_idle_force_poll || tick_check_broadcast_expired())) | |
cf37b6b4 NP |
53 | cpu_relax(); |
54 | trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); | |
55 | rcu_idle_exit(); | |
56 | return 1; | |
57 | } | |
58 | ||
59 | /* Weak implementations for optional arch specific functions */ | |
60 | void __weak arch_cpu_idle_prepare(void) { } | |
61 | void __weak arch_cpu_idle_enter(void) { } | |
62 | void __weak arch_cpu_idle_exit(void) { } | |
63 | void __weak arch_cpu_idle_dead(void) { } | |
64 | void __weak arch_cpu_idle(void) | |
65 | { | |
66 | cpu_idle_force_poll = 1; | |
67 | local_irq_enable(); | |
68 | } | |
69 | ||
30cdd69e DL |
70 | /** |
71 | * cpuidle_idle_call - the main idle function | |
72 | * | |
73 | * NOTE: no locks or semaphores should be used here | |
82c65d60 AL |
74 | * |
75 | * On archs that support TIF_POLLING_NRFLAG, is called with polling | |
76 | * set, and it returns with polling set. If it ever stops polling, it | |
77 | * must clear the polling bit. | |
30cdd69e | 78 | */ |
08c373e5 | 79 | static void cpuidle_idle_call(void) |
30cdd69e DL |
80 | { |
81 | struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices); | |
82 | struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); | |
37352273 | 83 | int next_state, entered_state; |
89abb5ad | 84 | unsigned int broadcast; |
30cdd69e | 85 | |
a1d028bd DL |
86 | /* |
87 | * Check if the idle task must be rescheduled. If it is the | |
c444117f | 88 | * case, exit the function after re-enabling the local irq. |
a1d028bd | 89 | */ |
c444117f | 90 | if (need_resched()) { |
8ca3c642 | 91 | local_irq_enable(); |
08c373e5 | 92 | return; |
8ca3c642 DL |
93 | } |
94 | ||
a1d028bd DL |
95 | /* |
96 | * During the idle period, stop measuring the disabled irqs | |
97 | * critical sections latencies | |
98 | */ | |
c8cc7d4d | 99 | stop_critical_timings(); |
a1d028bd DL |
100 | |
101 | /* | |
102 | * Tell the RCU framework we are entering an idle section, | |
103 | * so no more rcu read side critical sections and one more | |
104 | * step to the grace period | |
105 | */ | |
c8cc7d4d DL |
106 | rcu_idle_enter(); |
107 | ||
38106313 RW |
108 | /* |
109 | * Suspend-to-idle ("freeze") is a system state in which all user space | |
110 | * has been frozen, all I/O devices have been suspended and the only | |
111 | * activity happens here and in iterrupts (if any). In that case bypass | |
112 | * the cpuidle governor and go stratight for the deepest idle state | |
113 | * available. Possibly also suspend the local tick and the entire | |
114 | * timekeeping to prevent timer interrupts from kicking us out of idle | |
115 | * until a proper wakeup interrupt happens. | |
116 | */ | |
117 | if (idle_should_freeze()) { | |
118 | cpuidle_enter_freeze(); | |
119 | local_irq_enable(); | |
120 | goto exit_idle; | |
121 | } | |
122 | ||
a1d028bd | 123 | /* |
52c324f8 | 124 | * Ask the cpuidle framework to choose a convenient idle state. |
ec6e7f40 | 125 | * Fall back to the default arch idle method on errors. |
a1d028bd | 126 | */ |
52c324f8 | 127 | next_state = cpuidle_select(drv, dev); |
ec6e7f40 | 128 | if (next_state < 0) { |
37352273 | 129 | use_default: |
a1d028bd | 130 | /* |
37352273 PZ |
131 | * We can't use the cpuidle framework, let's use the default |
132 | * idle routine. | |
a1d028bd | 133 | */ |
37352273 | 134 | if (current_clr_polling_and_test()) |
8ca3c642 | 135 | local_irq_enable(); |
37352273 PZ |
136 | else |
137 | arch_cpu_idle(); | |
138 | ||
139 | goto exit_idle; | |
8ca3c642 DL |
140 | } |
141 | ||
37352273 PZ |
142 | |
143 | /* | |
144 | * The idle task must be scheduled, it is pointless to | |
145 | * go to idle, just update no idle residency and get | |
146 | * out of this function | |
147 | */ | |
148 | if (current_clr_polling_and_test()) { | |
149 | dev->last_residency = 0; | |
150 | entered_state = next_state; | |
151 | local_irq_enable(); | |
152 | goto exit_idle; | |
c444117f | 153 | } |
8ca3c642 | 154 | |
89abb5ad | 155 | broadcast = drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP; |
37352273 PZ |
156 | |
157 | /* | |
158 | * Tell the time framework to switch to a broadcast timer | |
159 | * because our local timer will be shutdown. If a local timer | |
160 | * is used from another cpu as a broadcast timer, this call may | |
161 | * fail if it is not available | |
162 | */ | |
163 | if (broadcast && | |
164 | clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu)) | |
165 | goto use_default; | |
166 | ||
442bf3aa DL |
167 | /* Take note of the planned idle state. */ |
168 | idle_set_state(this_rq(), &drv->states[next_state]); | |
169 | ||
37352273 PZ |
170 | /* |
171 | * Enter the idle state previously returned by the governor decision. | |
172 | * This function will block until an interrupt occurs and will take | |
173 | * care of re-enabling the local interrupts | |
174 | */ | |
175 | entered_state = cpuidle_enter(drv, dev, next_state); | |
176 | ||
442bf3aa DL |
177 | /* The cpu is no longer idle or about to enter idle. */ |
178 | idle_set_state(this_rq(), NULL); | |
179 | ||
37352273 PZ |
180 | if (broadcast) |
181 | clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu); | |
182 | ||
183 | /* | |
184 | * Give the governor an opportunity to reflect on the outcome | |
185 | */ | |
186 | cpuidle_reflect(dev, entered_state); | |
187 | ||
188 | exit_idle: | |
8ca3c642 | 189 | __current_set_polling(); |
30cdd69e | 190 | |
a1d028bd | 191 | /* |
37352273 | 192 | * It is up to the idle functions to reenable local interrupts |
a1d028bd | 193 | */ |
c8cc7d4d DL |
194 | if (WARN_ON_ONCE(irqs_disabled())) |
195 | local_irq_enable(); | |
196 | ||
197 | rcu_idle_exit(); | |
198 | start_critical_timings(); | |
30cdd69e | 199 | } |
30cdd69e | 200 | |
cf37b6b4 NP |
201 | /* |
202 | * Generic idle loop implementation | |
82c65d60 AL |
203 | * |
204 | * Called with polling cleared. | |
cf37b6b4 NP |
205 | */ |
206 | static void cpu_idle_loop(void) | |
207 | { | |
208 | while (1) { | |
82c65d60 AL |
209 | /* |
210 | * If the arch has a polling bit, we maintain an invariant: | |
211 | * | |
212 | * Our polling bit is clear if we're not scheduled (i.e. if | |
213 | * rq->curr != rq->idle). This means that, if rq->idle has | |
214 | * the polling bit set, then setting need_resched is | |
215 | * guaranteed to cause the cpu to reschedule. | |
216 | */ | |
217 | ||
218 | __current_set_polling(); | |
cf37b6b4 NP |
219 | tick_nohz_idle_enter(); |
220 | ||
221 | while (!need_resched()) { | |
222 | check_pgt_cache(); | |
223 | rmb(); | |
224 | ||
225 | if (cpu_is_offline(smp_processor_id())) | |
226 | arch_cpu_idle_dead(); | |
227 | ||
228 | local_irq_disable(); | |
229 | arch_cpu_idle_enter(); | |
230 | ||
231 | /* | |
232 | * In poll mode we reenable interrupts and spin. | |
233 | * | |
234 | * Also if we detected in the wakeup from idle | |
235 | * path that the tick broadcast device expired | |
236 | * for us, we don't want to go deep idle as we | |
237 | * know that the IPI is going to arrive right | |
238 | * away | |
239 | */ | |
8ca3c642 | 240 | if (cpu_idle_force_poll || tick_check_broadcast_expired()) |
cf37b6b4 | 241 | cpu_idle_poll(); |
8ca3c642 DL |
242 | else |
243 | cpuidle_idle_call(); | |
244 | ||
cf37b6b4 | 245 | arch_cpu_idle_exit(); |
cf37b6b4 | 246 | } |
06d50c65 PZ |
247 | |
248 | /* | |
249 | * Since we fell out of the loop above, we know | |
250 | * TIF_NEED_RESCHED must be set, propagate it into | |
251 | * PREEMPT_NEED_RESCHED. | |
252 | * | |
253 | * This is required because for polling idle loops we will | |
254 | * not have had an IPI to fold the state for us. | |
255 | */ | |
256 | preempt_set_need_resched(); | |
cf37b6b4 | 257 | tick_nohz_idle_exit(); |
82c65d60 AL |
258 | __current_clr_polling(); |
259 | ||
260 | /* | |
e3baac47 PZ |
261 | * We promise to call sched_ttwu_pending and reschedule |
262 | * if need_resched is set while polling is set. That | |
263 | * means that clearing polling needs to be visible | |
264 | * before doing these things. | |
82c65d60 AL |
265 | */ |
266 | smp_mb__after_atomic(); | |
267 | ||
e3baac47 | 268 | sched_ttwu_pending(); |
cf37b6b4 NP |
269 | schedule_preempt_disabled(); |
270 | } | |
271 | } | |
272 | ||
273 | void cpu_startup_entry(enum cpuhp_state state) | |
274 | { | |
275 | /* | |
276 | * This #ifdef needs to die, but it's too late in the cycle to | |
277 | * make this generic (arm and sh have never invoked the canary | |
278 | * init for the non boot cpus!). Will be fixed in 3.11 | |
279 | */ | |
280 | #ifdef CONFIG_X86 | |
281 | /* | |
282 | * If we're the non-boot CPU, nothing set the stack canary up | |
283 | * for us. The boot CPU already has it initialized but no harm | |
284 | * in doing it again. This is a good place for updating it, as | |
285 | * we wont ever return from this function (so the invalid | |
286 | * canaries already on the stack wont ever trigger). | |
287 | */ | |
288 | boot_init_stack_canary(); | |
289 | #endif | |
cf37b6b4 NP |
290 | arch_cpu_idle_prepare(); |
291 | cpu_idle_loop(); | |
292 | } |