include/linux/sched/idle.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_SCHED_IDLE_H
   3 #define _LINUX_SCHED_IDLE_H
   4
   5 #include <linux/sched.h>
   6
   7 enum cpu_idle_type {
   8         CPU_IDLE,
   9         CPU_NOT_IDLE,
  10         CPU_NEWLY_IDLE,
  11         CPU_MAX_IDLE_TYPES
  12 };
  13
  14 #ifdef CONFIG_SMP
  15 extern void wake_up_if_idle(int cpu);
  16 #else
  17 static inline void wake_up_if_idle(int cpu) { }
  18 #endif
  19
  20 /*
  21  * Idle thread specific functions to determine the need_resched
  22  * polling state.
  23  */
  24 #ifdef TIF_POLLING_NRFLAG
  25
  26 static inline void __current_set_polling(void)
  27 {
  28         set_thread_flag(TIF_POLLING_NRFLAG);
  29 }
  30
  31 static inline bool __must_check current_set_polling_and_test(void)
  32 {
  33         __current_set_polling();
  34
  35         /*
  36          * Polling state must be visible before we test NEED_RESCHED,
  37          * paired by resched_curr()
  38          */
  39         smp_mb__after_atomic();
  40
  41         return unlikely(tif_need_resched());
  42 }
  43
  44 static inline void __current_clr_polling(void)
  45 {
  46         clear_thread_flag(TIF_POLLING_NRFLAG);
  47 }
  48
  49 static inline bool __must_check current_clr_polling_and_test(void)
  50 {
  51         __current_clr_polling();
  52
  53         /*
  54          * Polling state must be visible before we test NEED_RESCHED,
  55          * paired by resched_curr()
  56          */
  57         smp_mb__after_atomic();
  58
  59         return unlikely(tif_need_resched());
  60 }
  61
  62 #else
  63 static inline void __current_set_polling(void) { }
  64 static inline void __current_clr_polling(void) { }
  65
  66 static inline bool __must_check current_set_polling_and_test(void)
  67 {
  68         return unlikely(tif_need_resched());
  69 }
  70 static inline bool __must_check current_clr_polling_and_test(void)
  71 {
  72         return unlikely(tif_need_resched());
  73 }
  74 #endif
  75
  76 static inline void current_clr_polling(void)
  77 {
  78         __current_clr_polling();
  79
  80         /*
  81          * Ensure we check TIF_NEED_RESCHED after we clear the polling bit.
  82          * Once the bit is cleared, we'll get IPIs with every new
  83          * TIF_NEED_RESCHED and the IPI handler, scheduler_ipi(), will also
  84          * fold.
  85          */
  86         smp_mb(); /* paired with resched_curr() */
  87
  88         preempt_fold_need_resched();
  89 }
  90
  91 #endif /* _LINUX_SCHED_IDLE_H */