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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __ASM_PREEMPT_H
3#define __ASM_PREEMPT_H
4
5#include <asm/rmwcc.h>
6#include <asm/percpu.h>
7#include <linux/thread_info.h>
8
9DECLARE_PER_CPU(int, __preempt_count);
10
11/*
12 * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
13 * that a decrement hitting 0 means we can and should reschedule.
14 */
15#define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
16
17/*
18 * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
19 * that think a non-zero value indicates we cannot preempt.
20 */
21static __always_inline int preempt_count(void)
22{
23 return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
24}
25
26static __always_inline void preempt_count_set(int pc)
27{
28 int old, new;
29
30 do {
31 old = raw_cpu_read_4(__preempt_count);
32 new = (old & PREEMPT_NEED_RESCHED) |
33 (pc & ~PREEMPT_NEED_RESCHED);
34 } while (raw_cpu_cmpxchg_4(__preempt_count, old, new) != old);
35}
36
37/*
38 * must be macros to avoid header recursion hell
39 */
40#define init_task_preempt_count(p) do { } while (0)
41
42#define init_idle_preempt_count(p, cpu) do { \
43 per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
44} while (0)
45
46/*
47 * We fold the NEED_RESCHED bit into the preempt count such that
48 * preempt_enable() can decrement and test for needing to reschedule with a
49 * single instruction.
50 *
51 * We invert the actual bit, so that when the decrement hits 0 we know we both
52 * need to resched (the bit is cleared) and can resched (no preempt count).
53 */
54
55static __always_inline void set_preempt_need_resched(void)
56{
57 raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
58}
59
60static __always_inline void clear_preempt_need_resched(void)
61{
62 raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
63}
64
65static __always_inline bool test_preempt_need_resched(void)
66{
67 return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
68}
69
70/*
71 * The various preempt_count add/sub methods
72 */
73
74static __always_inline void __preempt_count_add(int val)
75{
76 raw_cpu_add_4(__preempt_count, val);
77}
78
79static __always_inline void __preempt_count_sub(int val)
80{
81 raw_cpu_add_4(__preempt_count, -val);
82}
83
84/*
85 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
86 * a decrement which hits zero means we have no preempt_count and should
87 * reschedule.
88 */
89static __always_inline bool __preempt_count_dec_and_test(void)
90{
91 return GEN_UNARY_RMWcc("decl", __preempt_count, e, __percpu_arg([var]));
92}
93
94/*
95 * Returns true when we need to resched and can (barring IRQ state).
96 */
97static __always_inline bool should_resched(int preempt_offset)
98{
99 return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset);
100}
101
102#ifdef CONFIG_PREEMPT
103 extern asmlinkage void ___preempt_schedule(void);
104# define __preempt_schedule() \
105 asm volatile ("call ___preempt_schedule" : ASM_CALL_CONSTRAINT)
106
107 extern asmlinkage void preempt_schedule(void);
108 extern asmlinkage void ___preempt_schedule_notrace(void);
109# define __preempt_schedule_notrace() \
110 asm volatile ("call ___preempt_schedule_notrace" : ASM_CALL_CONSTRAINT)
111
112 extern asmlinkage void preempt_schedule_notrace(void);
113#endif
114
115#endif /* __ASM_PREEMPT_H */