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 extern void wake_up_if_idle(int cpu);
  15
  16 /*
  17  * Idle thread specific functions to determine the need_resched
  18  * polling state.
  19  */
  20 #ifdef TIF_POLLING_NRFLAG
  21
  22 static inline void __current_set_polling(void)
  23 {
  24         set_thread_flag(TIF_POLLING_NRFLAG);
  25 }
  26
  27 static inline bool __must_check current_set_polling_and_test(void)
  28 {
  29         __current_set_polling();
  30
  31         /*
  32          * Polling state must be visible before we test NEED_RESCHED,
  33          * paired by resched_curr()
  34          */
  35         smp_mb__after_atomic();
  36
  37         return unlikely(tif_need_resched());
  38 }
  39
  40 static inline void __current_clr_polling(void)
  41 {
  42         clear_thread_flag(TIF_POLLING_NRFLAG);
  43 }
  44
  45 static inline bool __must_check current_clr_polling_and_test(void)
  46 {
  47         __current_clr_polling();
  48
  49         /*
  50          * Polling state must be visible before we test NEED_RESCHED,
  51          * paired by resched_curr()
  52          */
  53         smp_mb__after_atomic();
  54
  55         return unlikely(tif_need_resched());
  56 }
  57
  58 #else
  59 static inline void __current_set_polling(void) { }
  60 static inline void __current_clr_polling(void) { }
  61
  62 static inline bool __must_check current_set_polling_and_test(void)
  63 {
  64         return unlikely(tif_need_resched());
  65 }
  66 static inline bool __must_check current_clr_polling_and_test(void)
  67 {
  68         return unlikely(tif_need_resched());
  69 }
  70 #endif
  71
  72 static inline void current_clr_polling(void)
  73 {
  74         __current_clr_polling();
  75
  76         /*
  77          * Ensure we check TIF_NEED_RESCHED after we clear the polling bit.
  78          * Once the bit is cleared, we'll get IPIs with every new
  79          * TIF_NEED_RESCHED and the IPI handler, scheduler_ipi(), will also
  80          * fold.
  81          */
  82         smp_mb(); /* paired with resched_curr() */
  83
  84         preempt_fold_need_resched();
  85 }
  86
  87 #endif /* _LINUX_SCHED_IDLE_H */