1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __ASM_PREEMPT_H
3 #define __ASM_PREEMPT_H
4
5 #include <asm/current.h>
6 #include <linux/thread_info.h>
7 #include <asm/atomic_ops.h>
8
9 #ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
10
11 /* We use the MSB mostly because its available */
12 #define PREEMPT_NEED_RESCHED 0x80000000
13 #define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
14
15 static __always_inline int preempt_count(void)
16 {
17 return READ_ONCE(get_lowcore()->preempt_count) & ~PREEMPT_NEED_RESCHED;
18 }
19
20 static __always_inline void preempt_count_set(int pc)
21 {
22 int old, new;
23
24 do {
25 old = READ_ONCE(get_lowcore()->preempt_count);
26 new = (old & PREEMPT_NEED_RESCHED) |
27 (pc & ~PREEMPT_NEED_RESCHED);
28 } while (__atomic_cmpxchg(&get_lowcore()->preempt_count,
29 old, new) != old);
30 }
31
32 static __always_inline void set_preempt_need_resched(void)
33 {
34 __atomic_and(~PREEMPT_NEED_RESCHED, &get_lowcore()->preempt_count);
35 }
36
37 static __always_inline void clear_preempt_need_resched(void)
38 {
39 __atomic_or(PREEMPT_NEED_RESCHED, &get_lowcore()->preempt_count);
40 }
41
42 static __always_inline bool test_preempt_need_resched(void)
43 {
44 return !(READ_ONCE(get_lowcore()->preempt_count) & PREEMPT_NEED_RESCHED);
45 }
46
47 static __always_inline void __preempt_count_add(int val)
48 {
49 /*
50 * With some obscure config options and CONFIG_PROFILE_ALL_BRANCHES
51 * enabled, gcc 12 fails to handle __builtin_constant_p().
52 */
53 if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES)) {
54 if (__builtin_constant_p(val) && (val >= -128) && (val <= 127)) {
55 __atomic_add_const(val, &get_lowcore()->preempt_count);
56 return;
57 }
58 }
59 __atomic_add(val, &get_lowcore()->preempt_count);
60 }
61
62 static __always_inline void __preempt_count_sub(int val)
63 {
64 __preempt_count_add(-val);
65 }
66
67 static __always_inline bool __preempt_count_dec_and_test(void)
68 {
69 return __atomic_add(-1, &get_lowcore()->preempt_count) == 1;
70 }
71
72 static __always_inline bool should_resched(int preempt_offset)
73 {
74 return unlikely(READ_ONCE(get_lowcore()->preempt_count) ==
75 preempt_offset);
76 }
77
78 #else /* CONFIG_HAVE_MARCH_Z196_FEATURES */
79
80 #define PREEMPT_ENABLED (0)
81
82 static __always_inline int preempt_count(void)
83 {
84 return READ_ONCE(get_lowcore()->preempt_count);
85 }
86
87 static __always_inline void preempt_count_set(int pc)
88 {
89 get_lowcore()->preempt_count = pc;
90 }
91
92 static __always_inline void set_preempt_need_resched(void)
93 {
94 }
95
96 static __always_inline void clear_preempt_need_resched(void)
97 {
98 }
99
100 static __always_inline bool test_preempt_need_resched(void)
101 {
102 return false;
103 }
104
105 static __always_inline void __preempt_count_add(int val)
106 {
107 get_lowcore()->preempt_count += val;
108 }
109
110 static __always_inline void __preempt_count_sub(int val)
111 {
112 get_lowcore()->preempt_count -= val;
113 }
114
115 static __always_inline bool __preempt_count_dec_and_test(void)
116 {
117 return !--get_lowcore()->preempt_count && tif_need_resched();
118 }
119
120 static __always_inline bool should_resched(int preempt_offset)
121 {
122 return unlikely(preempt_count() == preempt_offset &&
123 tif_need_resched());
124 }
125
126 #endif /* CONFIG_HAVE_MARCH_Z196_FEATURES */
127
128 #define init_task_preempt_count(p) do { } while (0)
129 /* Deferred to CPU bringup time */
130 #define init_idle_preempt_count(p, cpu) do { } while (0)
131
132 #ifdef CONFIG_PREEMPTION
133 extern void preempt_schedule(void);
134 #define __preempt_schedule() preempt_schedule()
135 extern void preempt_schedule_notrace(void);
136 #define __preempt_schedule_notrace() preempt_schedule_notrace()
137 #endif /* CONFIG_PREEMPTION */
138
139 #endif /* __ASM_PREEMPT_H */
140
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