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
83void preempt_schedule(void);
84#define __preempt_schedule() preempt_schedule()
85void preempt_schedule_notrace(void);
86#define __preempt_schedule_notrace() preempt_schedule_notrace()
87#endif /* CONFIG_PREEMPTION */
88
89#endif /* __ASM_PREEMPT_H */
90