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
  7enum cpu_idle_type {
  8	__CPU_NOT_IDLE = 0,
  9	CPU_IDLE,
 10	CPU_NEWLY_IDLE,
 11	CPU_MAX_IDLE_TYPES
 12};
 13
 14extern 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#ifdef _ASM_GENERIC_BITOPS_INSTRUMENTED_ATOMIC_H
 23
 24static __always_inline void __current_set_polling(void)
 25{
 26	arch_set_bit(TIF_POLLING_NRFLAG,
 27		     (unsigned long *)(&current_thread_info()->flags));
 28}
 29
 30static __always_inline void __current_clr_polling(void)
 31{
 32	arch_clear_bit(TIF_POLLING_NRFLAG,
 33		       (unsigned long *)(&current_thread_info()->flags));
 34}
 35
 36#else
 37
 38static __always_inline void __current_set_polling(void)
 39{
 40	set_bit(TIF_POLLING_NRFLAG,
 41		(unsigned long *)(&current_thread_info()->flags));
 42}
 43
 44static __always_inline void __current_clr_polling(void)
 45{
 46	clear_bit(TIF_POLLING_NRFLAG,
 47		  (unsigned long *)(&current_thread_info()->flags));
 48}
 49
 50#endif /* _ASM_GENERIC_BITOPS_INSTRUMENTED_ATOMIC_H */
 51
 52static __always_inline bool __must_check current_set_polling_and_test(void)
 53{
 54	__current_set_polling();
 55
 56	/*
 57	 * Polling state must be visible before we test NEED_RESCHED,
 58	 * paired by resched_curr()
 59	 */
 60	smp_mb__after_atomic();
 61
 62	return unlikely(tif_need_resched());
 63}
 64
 65static __always_inline bool __must_check current_clr_polling_and_test(void)
 66{
 67	__current_clr_polling();
 68
 69	/*
 70	 * Polling state must be visible before we test NEED_RESCHED,
 71	 * paired by resched_curr()
 72	 */
 73	smp_mb__after_atomic();
 74
 75	return unlikely(tif_need_resched());
 76}
 77
 78static __always_inline void current_clr_polling(void)
 79{
 80	__current_clr_polling();
 81
 82	/*
 83	 * Ensure we check TIF_NEED_RESCHED after we clear the polling bit.
 84	 * Once the bit is cleared, we'll get IPIs with every new
 85	 * TIF_NEED_RESCHED and the IPI handler, scheduler_ipi(), will also
 86	 * fold.
 87	 */
 88	smp_mb__after_atomic(); /* paired with resched_curr() */
 89
 90	preempt_fold_need_resched();
 91}
 92
 93#else
 94static inline void __current_set_polling(void) { }
 95static inline void __current_clr_polling(void) { }
 96
 97static inline bool __must_check current_set_polling_and_test(void)
 98{
 99	return unlikely(tif_need_resched());
100}
101static inline bool __must_check current_clr_polling_and_test(void)
102{
103	return unlikely(tif_need_resched());
104}
105
106static __always_inline void current_clr_polling(void)
107{
108	__current_clr_polling();
109
110	smp_mb(); /* paired with resched_curr() */
111
112	preempt_fold_need_resched();
113}
114#endif
115
116#endif /* _LINUX_SCHED_IDLE_H */