preempt.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef __ASM_PREEMPT_H
  3#define __ASM_PREEMPT_H
  4
  5#include <linux/thread_info.h>
  6
  7#define PREEMPT_NEED_RESCHED	BIT(32)
  8#define PREEMPT_ENABLED	(PREEMPT_NEED_RESCHED)
  9
 10static inline int preempt_count(void)
 11{
 12	return READ_ONCE(current_thread_info()->preempt.count);
 13}
 14
 15static inline void preempt_count_set(u64 pc)
 16{
 17	/* Preserve existing value of PREEMPT_NEED_RESCHED */
 18	WRITE_ONCE(current_thread_info()->preempt.count, pc);
 19}
 20
 21#define init_task_preempt_count(p) do { \
 22	task_thread_info(p)->preempt_count = FORK_PREEMPT_COUNT; \
 23} while (0)
 24
 25#define init_idle_preempt_count(p, cpu) do { \
 26	task_thread_info(p)->preempt_count = PREEMPT_DISABLED; \
 27} while (0)
 28
 29static inline void set_preempt_need_resched(void)
 30{
 31	current_thread_info()->preempt.need_resched = 0;
 32}
 33
 34static inline void clear_preempt_need_resched(void)
 35{
 36	current_thread_info()->preempt.need_resched = 1;
 37}
 38
 39static inline bool test_preempt_need_resched(void)
 40{
 41	return !current_thread_info()->preempt.need_resched;
 42}
 43
 44static inline void __preempt_count_add(int val)
 45{
 46	u32 pc = READ_ONCE(current_thread_info()->preempt.count);
 47	pc += val;
 48	WRITE_ONCE(current_thread_info()->preempt.count, pc);
 49}
 50
 51static inline void __preempt_count_sub(int val)
 52{
 53	u32 pc = READ_ONCE(current_thread_info()->preempt.count);
 54	pc -= val;
 55	WRITE_ONCE(current_thread_info()->preempt.count, pc);
 56}
 57
 58static inline bool __preempt_count_dec_and_test(void)
 59{
 60	struct thread_info *ti = current_thread_info();
 61	u64 pc = READ_ONCE(ti->preempt_count);
 62
 63	/* Update only the count field, leaving need_resched unchanged */
 64	WRITE_ONCE(ti->preempt.count, --pc);
 65
 66	/*
 67	 * If we wrote back all zeroes, then we're preemptible and in
 68	 * need of a reschedule. Otherwise, we need to reload the
 69	 * preempt_count in case the need_resched flag was cleared by an
 70	 * interrupt occurring between the non-atomic READ_ONCE/WRITE_ONCE
 71	 * pair.
 72	 */
 73	return !pc || !READ_ONCE(ti->preempt_count);
 74}
 75
 76static inline bool should_resched(int preempt_offset)
 77{
 78	u64 pc = READ_ONCE(current_thread_info()->preempt_count);
 79	return pc == preempt_offset;
 80}
 81
 82#ifdef CONFIG_PREEMPTION
 83
 84void preempt_schedule(void);
 85void preempt_schedule_notrace(void);
 86
 87#ifdef CONFIG_PREEMPT_DYNAMIC
 88
 89void dynamic_preempt_schedule(void);
 90#define __preempt_schedule()		dynamic_preempt_schedule()
 91void dynamic_preempt_schedule_notrace(void);
 92#define __preempt_schedule_notrace()	dynamic_preempt_schedule_notrace()
 93
 94#else /* CONFIG_PREEMPT_DYNAMIC */
 95
 96#define __preempt_schedule()		preempt_schedule()
 97#define __preempt_schedule_notrace()	preempt_schedule_notrace()
 98
 99#endif /* CONFIG_PREEMPT_DYNAMIC */
100#endif /* CONFIG_PREEMPTION */
101
102#endif /* __ASM_PREEMPT_H */