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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> | |
8df3e07e | 7 | #include <linux/cpuhotplug.h> |
cf37b6b4 NP |
8 | #include <linux/tick.h> |
9 | #include <linux/mm.h> | |
10 | #include <linux/stackprotector.h> | |
38106313 | 11 | #include <linux/suspend.h> |
cf37b6b4 NP |
12 | |
13 | #include <asm/tlb.h> | |
14 | ||
15 | #include <trace/events/power.h> | |
16 | ||
e3baac47 PZ |
17 | #include "sched.h" |
18 | ||
6727ad9e CM |
19 | /* Linker adds these: start and end of __cpuidle functions */ |
20 | extern char __cpuidle_text_start[], __cpuidle_text_end[]; | |
21 | ||
faad3849 RW |
22 | /** |
23 | * sched_idle_set_state - Record idle state for the current CPU. | |
24 | * @idle_state: State to record. | |
25 | */ | |
26 | void sched_idle_set_state(struct cpuidle_state *idle_state) | |
27 | { | |
28 | idle_set_state(this_rq(), idle_state); | |
29 | } | |
30 | ||
cf37b6b4 NP |
31 | static int __read_mostly cpu_idle_force_poll; |
32 | ||
33 | void 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 | |
44 | static 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 | ||
51 | static 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 | ||
6727ad9e | 59 | static noinline int __cpuidle cpu_idle_poll(void) |
cf37b6b4 NP |
60 | { |
61 | rcu_idle_enter(); | |
62 | trace_cpu_idle_rcuidle(0, smp_processor_id()); | |
63 | local_irq_enable(); | |
9babcd79 | 64 | stop_critical_timings(); |
ff6f2d29 PM |
65 | while (!tif_need_resched() && |
66 | (cpu_idle_force_poll || tick_check_broadcast_expired())) | |
cf37b6b4 | 67 | cpu_relax(); |
9babcd79 | 68 | start_critical_timings(); |
cf37b6b4 NP |
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 */ | |
75 | void __weak arch_cpu_idle_prepare(void) { } | |
76 | void __weak arch_cpu_idle_enter(void) { } | |
77 | void __weak arch_cpu_idle_exit(void) { } | |
78 | void __weak arch_cpu_idle_dead(void) { } | |
79 | void __weak arch_cpu_idle(void) | |
80 | { | |
81 | cpu_idle_force_poll = 1; | |
82 | local_irq_enable(); | |
83 | } | |
84 | ||
827a5aef RW |
85 | /** |
86 | * default_idle_call - Default CPU idle routine. | |
87 | * | |
88 | * To use when the cpuidle framework cannot be used. | |
89 | */ | |
6727ad9e | 90 | void __cpuidle default_idle_call(void) |
82f66327 | 91 | { |
63caae84 | 92 | if (current_clr_polling_and_test()) { |
82f66327 | 93 | local_irq_enable(); |
63caae84 LS |
94 | } else { |
95 | stop_critical_timings(); | |
82f66327 | 96 | arch_cpu_idle(); |
63caae84 LS |
97 | start_critical_timings(); |
98 | } | |
82f66327 RW |
99 | } |
100 | ||
bcf6ad8a RW |
101 | static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev, |
102 | int next_state) | |
103 | { | |
bcf6ad8a RW |
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 | ||
bcf6ad8a RW |
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 | */ | |
827a5aef | 119 | return cpuidle_enter(drv, dev, next_state); |
bcf6ad8a RW |
120 | } |
121 | ||
30cdd69e DL |
122 | /** |
123 | * cpuidle_idle_call - the main idle function | |
124 | * | |
125 | * NOTE: no locks or semaphores should be used here | |
82c65d60 AL |
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. | |
30cdd69e | 130 | */ |
08c373e5 | 131 | static void cpuidle_idle_call(void) |
30cdd69e | 132 | { |
9bd616e3 | 133 | struct cpuidle_device *dev = cpuidle_get_device(); |
30cdd69e | 134 | struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); |
37352273 | 135 | int next_state, entered_state; |
30cdd69e | 136 | |
a1d028bd DL |
137 | /* |
138 | * Check if the idle task must be rescheduled. If it is the | |
c444117f | 139 | * case, exit the function after re-enabling the local irq. |
a1d028bd | 140 | */ |
c444117f | 141 | if (need_resched()) { |
8ca3c642 | 142 | local_irq_enable(); |
08c373e5 | 143 | return; |
8ca3c642 DL |
144 | } |
145 | ||
a1d028bd DL |
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 | */ | |
c8cc7d4d DL |
151 | rcu_idle_enter(); |
152 | ||
82f66327 RW |
153 | if (cpuidle_not_available(drv, dev)) { |
154 | default_idle_call(); | |
155 | goto exit_idle; | |
156 | } | |
ef2b22ac | 157 | |
38106313 RW |
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 | if (idle_should_freeze()) { | |
ef2b22ac | 168 | entered_state = cpuidle_enter_freeze(drv, dev); |
6f16886b | 169 | if (entered_state > 0) { |
ef2b22ac RW |
170 | local_irq_enable(); |
171 | goto exit_idle; | |
172 | } | |
173 | ||
ef2b22ac | 174 | next_state = cpuidle_find_deepest_state(drv, dev); |
bcf6ad8a | 175 | call_cpuidle(drv, dev, next_state); |
ef2b22ac | 176 | } else { |
ef2b22ac RW |
177 | /* |
178 | * Ask the cpuidle framework to choose a convenient idle state. | |
179 | */ | |
180 | next_state = cpuidle_select(drv, dev); | |
bcf6ad8a RW |
181 | entered_state = call_cpuidle(drv, dev, next_state); |
182 | /* | |
183 | * Give the governor an opportunity to reflect on the outcome | |
184 | */ | |
ef2b22ac | 185 | cpuidle_reflect(dev, entered_state); |
bcf6ad8a | 186 | } |
37352273 PZ |
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(); | |
30cdd69e | 198 | } |
30cdd69e | 199 | |
cf37b6b4 NP |
200 | /* |
201 | * Generic idle loop implementation | |
82c65d60 AL |
202 | * |
203 | * Called with polling cleared. | |
cf37b6b4 NP |
204 | */ |
205 | static void cpu_idle_loop(void) | |
206 | { | |
df55f462 GJGJ |
207 | int cpu = smp_processor_id(); |
208 | ||
cf37b6b4 | 209 | while (1) { |
82c65d60 AL |
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 | |
214 | * rq->curr != rq->idle). This means that, if rq->idle has | |
215 | * the polling bit set, then setting need_resched is | |
216 | * guaranteed to cause the cpu to reschedule. | |
217 | */ | |
218 | ||
219 | __current_set_polling(); | |
0eb77e98 | 220 | quiet_vmstat(); |
cf37b6b4 NP |
221 | tick_nohz_idle_enter(); |
222 | ||
223 | while (!need_resched()) { | |
224 | check_pgt_cache(); | |
225 | rmb(); | |
226 | ||
df55f462 | 227 | if (cpu_is_offline(cpu)) { |
e69aab13 | 228 | cpuhp_report_idle_dead(); |
cf37b6b4 | 229 | arch_cpu_idle_dead(); |
528a25b0 | 230 | } |
cf37b6b4 NP |
231 | |
232 | local_irq_disable(); | |
233 | arch_cpu_idle_enter(); | |
234 | ||
235 | /* | |
236 | * In poll mode we reenable interrupts and spin. | |
237 | * | |
238 | * Also if we detected in the wakeup from idle | |
239 | * path that the tick broadcast device expired | |
240 | * for us, we don't want to go deep idle as we | |
241 | * know that the IPI is going to arrive right | |
242 | * away | |
243 | */ | |
8ca3c642 | 244 | if (cpu_idle_force_poll || tick_check_broadcast_expired()) |
cf37b6b4 | 245 | cpu_idle_poll(); |
8ca3c642 DL |
246 | else |
247 | cpuidle_idle_call(); | |
248 | ||
cf37b6b4 | 249 | arch_cpu_idle_exit(); |
cf37b6b4 | 250 | } |
06d50c65 PZ |
251 | |
252 | /* | |
253 | * Since we fell out of the loop above, we know | |
254 | * TIF_NEED_RESCHED must be set, propagate it into | |
255 | * PREEMPT_NEED_RESCHED. | |
256 | * | |
257 | * This is required because for polling idle loops we will | |
258 | * not have had an IPI to fold the state for us. | |
259 | */ | |
260 | preempt_set_need_resched(); | |
cf37b6b4 | 261 | tick_nohz_idle_exit(); |
82c65d60 AL |
262 | __current_clr_polling(); |
263 | ||
264 | /* | |
e3baac47 PZ |
265 | * We promise to call sched_ttwu_pending and reschedule |
266 | * if need_resched is set while polling is set. That | |
267 | * means that clearing polling needs to be visible | |
268 | * before doing these things. | |
82c65d60 AL |
269 | */ |
270 | smp_mb__after_atomic(); | |
271 | ||
e3baac47 | 272 | sched_ttwu_pending(); |
cf37b6b4 NP |
273 | schedule_preempt_disabled(); |
274 | } | |
275 | } | |
276 | ||
6727ad9e CM |
277 | bool cpu_in_idle(unsigned long pc) |
278 | { | |
279 | return pc >= (unsigned long)__cpuidle_text_start && | |
280 | pc < (unsigned long)__cpuidle_text_end; | |
281 | } | |
282 | ||
cf37b6b4 NP |
283 | void cpu_startup_entry(enum cpuhp_state state) |
284 | { | |
285 | /* | |
286 | * This #ifdef needs to die, but it's too late in the cycle to | |
287 | * make this generic (arm and sh have never invoked the canary | |
288 | * init for the non boot cpus!). Will be fixed in 3.11 | |
289 | */ | |
290 | #ifdef CONFIG_X86 | |
291 | /* | |
292 | * If we're the non-boot CPU, nothing set the stack canary up | |
293 | * for us. The boot CPU already has it initialized but no harm | |
294 | * in doing it again. This is a good place for updating it, as | |
295 | * we wont ever return from this function (so the invalid | |
296 | * canaries already on the stack wont ever trigger). | |
297 | */ | |
298 | boot_init_stack_canary(); | |
299 | #endif | |
cf37b6b4 | 300 | arch_cpu_idle_prepare(); |
8df3e07e | 301 | cpuhp_online_idle(state); |
cf37b6b4 NP |
302 | cpu_idle_loop(); |
303 | } |