Pileus Git - ~andy/linux/blob - kernel/cpu/idle.c

   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
   9 #include <asm/tlb.h>
  10
  11 #include <trace/events/power.h>
  12
  13 #ifndef CONFIG_GENERIC_IDLE_LOOP
  14 void cpu_startup_entry(enum cpuhp_state state)
  15 {
  16         cpu_idle();
  17 }
  18 #else
  19
  20 static int __read_mostly cpu_idle_force_poll;
  21
  22 void cpu_idle_poll_ctrl(bool enable)
  23 {
  24         if (enable) {
  25                 cpu_idle_force_poll++;
  26         } else {
  27                 cpu_idle_force_poll--;
  28                 WARN_ON_ONCE(cpu_idle_force_poll < 0);
  29         }
  30 }
  31
  32 #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
  33 static int __init cpu_idle_poll_setup(char *__unused)
  34 {
  35         cpu_idle_force_poll = 1;
  36         return 1;
  37 }
  38 __setup("nohlt", cpu_idle_poll_setup);
  39
  40 static int __init cpu_idle_nopoll_setup(char *__unused)
  41 {
  42         cpu_idle_force_poll = 0;
  43         return 1;
  44 }
  45 __setup("hlt", cpu_idle_nopoll_setup);
  46 #endif
  47
  48 static inline int cpu_idle_poll(void)
  49 {
  50         trace_cpu_idle_rcuidle(0, smp_processor_id());
  51         local_irq_enable();
  52         while (!need_resched())
  53                 cpu_relax();
  54         trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
  55         return 1;
  56 }
  57
  58 /* Weak implementations for optional arch specific functions */
  59 void __weak arch_cpu_idle_prepare(void) { }
  60 void __weak arch_cpu_idle_enter(void) { }
  61 void __weak arch_cpu_idle_exit(void) { }
  62 void __weak arch_cpu_idle_dead(void) { }
  63 void __weak arch_cpu_idle(void)
  64 {
  65         cpu_idle_force_poll = 1;
  66 }
  67
  68 /*
  69  * Generic idle loop implementation
  70  */
  71 static void cpu_idle_loop(void)
  72 {
  73         while (1) {
  74                 tick_nohz_idle_enter();
  75
  76                 while (!need_resched()) {
  77                         check_pgt_cache();
  78                         rmb();
  79
  80                         if (cpu_is_offline(smp_processor_id()))
  81                                 arch_cpu_idle_dead();
  82
  83                         local_irq_disable();
  84                         arch_cpu_idle_enter();
  85
  86                         if (cpu_idle_force_poll) {
  87                                 cpu_idle_poll();
  88                         } else {
  89                                 current_clr_polling();
  90                                 if (!need_resched()) {
  91                                         stop_critical_timings();
  92                                         rcu_idle_enter();
  93                                         arch_cpu_idle();
  94                                         WARN_ON_ONCE(irqs_disabled());
  95                                         rcu_idle_exit();
  96                                         start_critical_timings();
  97                                 } else {
  98                                         local_irq_enable();
  99                                 }
 100                                 current_set_polling();
 101                         }
 102                         arch_cpu_idle_exit();
 103                 }
 104                 tick_nohz_idle_exit();
 105                 schedule_preempt_disabled();
 106         }
 107 }
 108
 109 void cpu_startup_entry(enum cpuhp_state state)
 110 {
 111         current_set_polling();
 112         arch_cpu_idle_prepare();
 113         cpu_idle_loop();
 114 }
 115 #endif