projects/linux·blob v3.13 · refs

141 lines · 3.2 KiB

1/*
2 * Generic entry point for the idle threads
3 */
4#include <linux/sched.h>
5#include <linux/cpu.h>
6#include <linux/tick.h>
7#include <linux/mm.h>
8#include <linux/stackprotector.h>
9
10#include <asm/tlb.h>
11
12#include <trace/events/power.h>
13
14static int __read_mostly cpu_idle_force_poll;
15
16void cpu_idle_poll_ctrl(bool enable)
17{
18 if (enable) {
19 cpu_idle_force_poll++;
20 } else {
21 cpu_idle_force_poll--;
22 WARN_ON_ONCE(cpu_idle_force_poll < 0);
23 }
24}
25
26#ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
27static int __init cpu_idle_poll_setup(char *__unused)
28{
29 cpu_idle_force_poll = 1;
30 return 1;
31}
32__setup("nohlt", cpu_idle_poll_setup);
33
34static int __init cpu_idle_nopoll_setup(char *__unused)
35{
36 cpu_idle_force_poll = 0;
37 return 1;
38}
39__setup("hlt", cpu_idle_nopoll_setup);
40#endif
41
42static inline int cpu_idle_poll(void)
43{
44 rcu_idle_enter();
45 trace_cpu_idle_rcuidle(0, smp_processor_id());
46 local_irq_enable();
47 while (!tif_need_resched())
48 cpu_relax();
49 trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
50 rcu_idle_exit();
51 return 1;
52}
53
54/* Weak implementations for optional arch specific functions */
55void __weak arch_cpu_idle_prepare(void) { }
56void __weak arch_cpu_idle_enter(void) { }
57void __weak arch_cpu_idle_exit(void) { }
58void __weak arch_cpu_idle_dead(void) { }
59void __weak arch_cpu_idle(void)
60{
61 cpu_idle_force_poll = 1;
62 local_irq_enable();
63}
64
65/*
66 * Generic idle loop implementation
67 */
68static void cpu_idle_loop(void)
69{
70 while (1) {
71 tick_nohz_idle_enter();
72
73 while (!need_resched()) {
74 check_pgt_cache();
75 rmb();
76
77 if (cpu_is_offline(smp_processor_id()))
78 arch_cpu_idle_dead();
79
80 local_irq_disable();
81 arch_cpu_idle_enter();
82
83 /*
84 * In poll mode we reenable interrupts and spin.
85 *
86 * Also if we detected in the wakeup from idle
87 * path that the tick broadcast device expired
88 * for us, we don't want to go deep idle as we
89 * know that the IPI is going to arrive right
90 * away
91 */
92 if (cpu_idle_force_poll || tick_check_broadcast_expired()) {
93 cpu_idle_poll();
94 } else {
95 if (!current_clr_polling_and_test()) {
96 stop_critical_timings();
97 rcu_idle_enter();
98 arch_cpu_idle();
99 WARN_ON_ONCE(irqs_disabled());
100 rcu_idle_exit();
101 start_critical_timings();
102 } else {
103 local_irq_enable();
104 }
105 __current_set_polling();
106 }
107 arch_cpu_idle_exit();
108 /*
109 * We need to test and propagate the TIF_NEED_RESCHED
110 * bit here because we might not have send the
111 * reschedule IPI to idle tasks.
112 */
113 if (tif_need_resched())
114 set_preempt_need_resched();
115 }
116 tick_nohz_idle_exit();
117 schedule_preempt_disabled();
118 }
119}
120
121void cpu_startup_entry(enum cpuhp_state state)
122{
123 /*
124 * This #ifdef needs to die, but it's too late in the cycle to
125 * make this generic (arm and sh have never invoked the canary
126 * init for the non boot cpus!). Will be fixed in 3.11
127 */
128#ifdef CONFIG_X86
129 /*
130 * If we're the non-boot CPU, nothing set the stack canary up
131 * for us. The boot CPU already has it initialized but no harm
132 * in doing it again. This is a good place for updating it, as
133 * we wont ever return from this function (so the invalid
134 * canaries already on the stack wont ever trigger).
135 */
136 boot_init_stack_canary();
137#endif
138 __current_set_polling();
139 arch_cpu_idle_prepare();
140 cpu_idle_loop();
141}