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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> | |
10 | ||
11 | #include <asm/tlb.h> | |
12 | ||
13 | #include <trace/events/power.h> | |
14 | ||
15 | static int __read_mostly cpu_idle_force_poll; | |
16 | ||
17 | void 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 | |
28 | static 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 | ||
35 | static 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 | ||
43 | static 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 */ | |
56 | void __weak arch_cpu_idle_prepare(void) { } | |
57 | void __weak arch_cpu_idle_enter(void) { } | |
58 | void __weak arch_cpu_idle_exit(void) { } | |
59 | void __weak arch_cpu_idle_dead(void) { } | |
60 | void __weak arch_cpu_idle(void) | |
61 | { | |
62 | cpu_idle_force_poll = 1; | |
63 | local_irq_enable(); | |
64 | } | |
65 | ||
30cdd69e DL |
66 | #ifdef CONFIG_CPU_IDLE |
67 | /** | |
68 | * cpuidle_idle_call - the main idle function | |
69 | * | |
70 | * NOTE: no locks or semaphores should be used here | |
71 | * return non-zero on failure | |
72 | */ | |
73 | static int cpuidle_idle_call(void) | |
74 | { | |
75 | struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices); | |
76 | struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); | |
77 | int next_state, entered_state, ret; | |
78 | bool broadcast; | |
79 | ||
80 | ret = cpuidle_enabled(drv, dev); | |
81 | if (ret < 0) | |
82 | return ret; | |
83 | ||
84 | /* ask the governor for the next state */ | |
85 | next_state = cpuidle_select(drv, dev); | |
86 | ||
87 | if (need_resched()) { | |
88 | dev->last_residency = 0; | |
89 | /* give the governor an opportunity to reflect on the outcome */ | |
90 | cpuidle_reflect(dev, next_state); | |
91 | local_irq_enable(); | |
92 | return 0; | |
93 | } | |
94 | ||
95 | broadcast = !!(drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP); | |
96 | ||
97 | if (broadcast && | |
98 | clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu)) | |
99 | return -EBUSY; | |
100 | ||
101 | trace_cpu_idle_rcuidle(next_state, dev->cpu); | |
102 | ||
103 | entered_state = cpuidle_enter(drv, dev, next_state); | |
104 | ||
105 | trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu); | |
106 | ||
107 | if (broadcast) | |
108 | clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu); | |
109 | ||
110 | /* give the governor an opportunity to reflect on the outcome */ | |
111 | cpuidle_reflect(dev, entered_state); | |
112 | ||
113 | return 0; | |
114 | } | |
115 | #else | |
116 | static inline int cpuidle_idle_call(void) | |
117 | { | |
118 | return -ENODEV; | |
119 | } | |
120 | #endif | |
121 | ||
cf37b6b4 NP |
122 | /* |
123 | * Generic idle loop implementation | |
124 | */ | |
125 | static void cpu_idle_loop(void) | |
126 | { | |
127 | while (1) { | |
128 | tick_nohz_idle_enter(); | |
129 | ||
130 | while (!need_resched()) { | |
131 | check_pgt_cache(); | |
132 | rmb(); | |
133 | ||
134 | if (cpu_is_offline(smp_processor_id())) | |
135 | arch_cpu_idle_dead(); | |
136 | ||
137 | local_irq_disable(); | |
138 | arch_cpu_idle_enter(); | |
139 | ||
140 | /* | |
141 | * In poll mode we reenable interrupts and spin. | |
142 | * | |
143 | * Also if we detected in the wakeup from idle | |
144 | * path that the tick broadcast device expired | |
145 | * for us, we don't want to go deep idle as we | |
146 | * know that the IPI is going to arrive right | |
147 | * away | |
148 | */ | |
149 | if (cpu_idle_force_poll || tick_check_broadcast_expired()) { | |
150 | cpu_idle_poll(); | |
151 | } else { | |
152 | if (!current_clr_polling_and_test()) { | |
153 | stop_critical_timings(); | |
154 | rcu_idle_enter(); | |
155 | if (cpuidle_idle_call()) | |
156 | arch_cpu_idle(); | |
157 | if (WARN_ON_ONCE(irqs_disabled())) | |
158 | local_irq_enable(); | |
159 | rcu_idle_exit(); | |
160 | start_critical_timings(); | |
161 | } else { | |
162 | local_irq_enable(); | |
163 | } | |
164 | __current_set_polling(); | |
165 | } | |
166 | arch_cpu_idle_exit(); | |
cf37b6b4 | 167 | } |
06d50c65 PZ |
168 | |
169 | /* | |
170 | * Since we fell out of the loop above, we know | |
171 | * TIF_NEED_RESCHED must be set, propagate it into | |
172 | * PREEMPT_NEED_RESCHED. | |
173 | * | |
174 | * This is required because for polling idle loops we will | |
175 | * not have had an IPI to fold the state for us. | |
176 | */ | |
177 | preempt_set_need_resched(); | |
cf37b6b4 NP |
178 | tick_nohz_idle_exit(); |
179 | schedule_preempt_disabled(); | |
180 | } | |
181 | } | |
182 | ||
183 | void cpu_startup_entry(enum cpuhp_state state) | |
184 | { | |
185 | /* | |
186 | * This #ifdef needs to die, but it's too late in the cycle to | |
187 | * make this generic (arm and sh have never invoked the canary | |
188 | * init for the non boot cpus!). Will be fixed in 3.11 | |
189 | */ | |
190 | #ifdef CONFIG_X86 | |
191 | /* | |
192 | * If we're the non-boot CPU, nothing set the stack canary up | |
193 | * for us. The boot CPU already has it initialized but no harm | |
194 | * in doing it again. This is a good place for updating it, as | |
195 | * we wont ever return from this function (so the invalid | |
196 | * canaries already on the stack wont ever trigger). | |
197 | */ | |
198 | boot_init_stack_canary(); | |
199 | #endif | |
200 | __current_set_polling(); | |
201 | arch_cpu_idle_prepare(); | |
202 | cpu_idle_loop(); | |
203 | } |