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 static int __read_mostly cpu_idle_force_poll;
  14
  15 void cpu_idle_poll_ctrl(bool enable)
  16 {
  17         if (enable) {
  18                 cpu_idle_force_poll++;
  19         } else {
  20                 cpu_idle_force_poll--;
  21                 WARN_ON_ONCE(cpu_idle_force_poll < 0);
  22         }
  23 }
  24
  25 #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
  26 static int __init cpu_idle_poll_setup(char *__unused)
  27 {
  28         cpu_idle_force_poll = 1;
  29         return 1;
  30 }
  31 __setup("nohlt", cpu_idle_poll_setup);
  32
  33 static int __init cpu_idle_nopoll_setup(char *__unused)
  34 {
  35         cpu_idle_force_poll = 0;
  36         return 1;
  37 }
  38 __setup("hlt", cpu_idle_nopoll_setup);
  39 #endif
  40
  41 static inline int cpu_idle_poll(void)
  42 {
  43         trace_cpu_idle_rcuidle(0, smp_processor_id());
  44         local_irq_enable();
  45         while (!need_resched())
  46                 cpu_relax();
  47         trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
  48         return 1;
  49 }
  50
  51 /* Weak implementations for optional arch specific functions */
  52 void __weak arch_cpu_idle_prepare(void) { }
  53 void __weak arch_cpu_idle_enter(void) { }
  54 void __weak arch_cpu_idle_exit(void) { }
  55 void __weak arch_cpu_idle_dead(void) { }
  56 void __weak arch_cpu_idle(void)
  57 {
  58         cpu_idle_force_poll = 1;
  59 }
  60
  61 /*
  62  * Generic idle loop implementation
  63  */
  64 static void cpu_idle_loop(void)
  65 {
  66         while (1) {
  67                 tick_nohz_idle_enter();
  68
  69                 while (!need_resched()) {
  70                         check_pgt_cache();
  71                         rmb();
  72
  73                         if (cpu_is_offline(smp_processor_id()))
  74                                 arch_cpu_idle_dead();
  75
  76                         local_irq_disable();
  77                         arch_cpu_idle_enter();
  78
  79                         /*
  80                          * In poll mode we reenable interrupts and spin.
  81                          *
  82                          * Also if we detected in the wakeup from idle
  83                          * path that the tick broadcast device expired
  84                          * for us, we don't want to go deep idle as we
  85                          * know that the IPI is going to arrive right
  86                          * away
  87                          */
  88                         if (cpu_idle_force_poll || tick_check_broadcast_expired()) {
  89                                 cpu_idle_poll();
  90                         } else {
  91                                 current_clr_polling();
  92                                 if (!need_resched()) {
  93                                         stop_critical_timings();
  94                                         rcu_idle_enter();
  95                                         arch_cpu_idle();
  96                                         WARN_ON_ONCE(irqs_disabled());
  97                                         rcu_idle_exit();
  98                                         start_critical_timings();
  99                                 } else {
 100                                         local_irq_enable();
 101                                 }
 102                                 current_set_polling();
 103                         }
 104                         arch_cpu_idle_exit();
 105                 }
 106                 tick_nohz_idle_exit();
 107                 schedule_preempt_disabled();
 108         }
 109 }
 110
 111 void cpu_startup_entry(enum cpuhp_state state)
 112 {
 113         current_set_polling();
 114         arch_cpu_idle_prepare();
 115         cpu_idle_loop();
 116 }