1#ifndef __ASM_PREEMPT_H
2#define __ASM_PREEMPT_H
3
4#include <asm/rmwcc.h>
5#include <asm/percpu.h>
6#include <linux/thread_info.h>
7
8DECLARE_PER_CPU(int, __preempt_count);
9
10/*
11 * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
12 * that a decrement hitting 0 means we can and should reschedule.
13 */
14#define PREEMPT_ENABLED	(0 + PREEMPT_NEED_RESCHED)
15
16/*
17 * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
18 * that think a non-zero value indicates we cannot preempt.
19 */
20static __always_inline int preempt_count(void)
21{
22	return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
23}
24
25static __always_inline void preempt_count_set(int pc)
26{
27	raw_cpu_write_4(__preempt_count, pc);
28}
29
30/*
31 * must be macros to avoid header recursion hell
32 */
33#define init_task_preempt_count(p) do { } while (0)
34
35#define init_idle_preempt_count(p, cpu) do { \
36	per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
37} while (0)
38
39/*
40 * We fold the NEED_RESCHED bit into the preempt count such that
41 * preempt_enable() can decrement and test for needing to reschedule with a
42 * single instruction.
43 *
44 * We invert the actual bit, so that when the decrement hits 0 we know we both
45 * need to resched (the bit is cleared) and can resched (no preempt count).
46 */
47
48static __always_inline void set_preempt_need_resched(void)
49{
50	raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
51}
52
53static __always_inline void clear_preempt_need_resched(void)
54{
55	raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
56}
57
58static __always_inline bool test_preempt_need_resched(void)
59{
60	return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
61}
62
63/*
64 * The various preempt_count add/sub methods
65 */
66
67static __always_inline void __preempt_count_add(int val)
68{
69	raw_cpu_add_4(__preempt_count, val);
70}
71
72static __always_inline void __preempt_count_sub(int val)
73{
74	raw_cpu_add_4(__preempt_count, -val);
75}
76
77/*
78 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
79 * a decrement which hits zero means we have no preempt_count and should
80 * reschedule.
81 */
82static __always_inline bool __preempt_count_dec_and_test(void)
83{
84	GEN_UNARY_RMWcc("decl", __preempt_count, __percpu_arg(0), "e");
85}
86
87/*
88 * Returns true when we need to resched and can (barring IRQ state).
89 */
90static __always_inline bool should_resched(int preempt_offset)
91{
92	return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset);
93}
94
95#ifdef CONFIG_PREEMPT
96  extern asmlinkage void ___preempt_schedule(void);
97# define __preempt_schedule() asm ("call ___preempt_schedule")
98  extern asmlinkage void preempt_schedule(void);
99  extern asmlinkage void ___preempt_schedule_notrace(void);
100# define __preempt_schedule_notrace() asm ("call ___preempt_schedule_notrace")
101  extern asmlinkage void preempt_schedule_notrace(void);
102#endif
103
104#endif /* __ASM_PREEMPT_H */
105