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
15static __always_inline int preempt_count(void)
16{
17	return READ_ONCE(S390_lowcore.preempt_count) & ~PREEMPT_NEED_RESCHED;
18}
19
20static __always_inline void preempt_count_set(int pc)
21{
22	int old, new;
23
24	do {
25		old = READ_ONCE(S390_lowcore.preempt_count);
26		new = (old & PREEMPT_NEED_RESCHED) |
27			(pc & ~PREEMPT_NEED_RESCHED);
28	} while (__atomic_cmpxchg(&S390_lowcore.preempt_count,
29				  old, new) != old);
30}
31
32static __always_inline void set_preempt_need_resched(void)
33{
34	__atomic_and(~PREEMPT_NEED_RESCHED, &S390_lowcore.preempt_count);
35}
36
37static __always_inline void clear_preempt_need_resched(void)
38{
39	__atomic_or(PREEMPT_NEED_RESCHED, &S390_lowcore.preempt_count);
40}
41
42static __always_inline bool test_preempt_need_resched(void)
43{
44	return !(READ_ONCE(S390_lowcore.preempt_count) & PREEMPT_NEED_RESCHED);
45}
46
47static __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, &S390_lowcore.preempt_count);
56			return;
57		}
58	}
59	__atomic_add(val, &S390_lowcore.preempt_count);
60}
61
62static __always_inline void __preempt_count_sub(int val)
63{
64	__preempt_count_add(-val);
65}
66
67static __always_inline bool __preempt_count_dec_and_test(void)
68{
69	return __atomic_add(-1, &S390_lowcore.preempt_count) == 1;
70}
71
72static __always_inline bool should_resched(int preempt_offset)
73{
74	return unlikely(READ_ONCE(S390_lowcore.preempt_count) ==
75			preempt_offset);
76}
77
78#else /* CONFIG_HAVE_MARCH_Z196_FEATURES */
79
80#define PREEMPT_ENABLED	(0)
81
82static __always_inline int preempt_count(void)
83{
84	return READ_ONCE(S390_lowcore.preempt_count);
85}
86
87static __always_inline void preempt_count_set(int pc)
88{
89	S390_lowcore.preempt_count = pc;
90}
91
92static __always_inline void set_preempt_need_resched(void)
93{
94}
95
96static __always_inline void clear_preempt_need_resched(void)
97{
98}
99
100static __always_inline bool test_preempt_need_resched(void)
101{
102	return false;
103}
104
105static __always_inline void __preempt_count_add(int val)
106{
107	S390_lowcore.preempt_count += val;
108}
109
110static __always_inline void __preempt_count_sub(int val)
111{
112	S390_lowcore.preempt_count -= val;
113}
114
115static __always_inline bool __preempt_count_dec_and_test(void)
116{
117	return !--S390_lowcore.preempt_count && tif_need_resched();
118}
119
120static __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
133extern void preempt_schedule(void);
134#define __preempt_schedule() preempt_schedule()
135extern void preempt_schedule_notrace(void);
136#define __preempt_schedule_notrace() preempt_schedule_notrace()
137#endif /* CONFIG_PREEMPTION */
138
139#endif /* __ASM_PREEMPT_H */
140