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 | |
9 | DECLARE_PER_CPU(int, __preempt_count); |
10 | |
11 | /* We use the MSB mostly because its available */ |
12 | #define PREEMPT_NEED_RESCHED 0x80000000 |
13 | |
14 | /* |
15 | * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such |
16 | * that a decrement hitting 0 means we can and should reschedule. |
17 | */ |
18 | #define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED) |
19 | |
20 | /* |
21 | * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users |
22 | * that think a non-zero value indicates we cannot preempt. |
23 | */ |
24 | static __always_inline int preempt_count(void) |
25 | { |
26 | return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED; |
27 | } |
28 | |
29 | static __always_inline void preempt_count_set(int pc) |
30 | { |
31 | int old, new; |
32 | |
33 | do { |
34 | old = raw_cpu_read_4(__preempt_count); |
35 | new = (old & PREEMPT_NEED_RESCHED) | |
36 | (pc & ~PREEMPT_NEED_RESCHED); |
37 | } while (raw_cpu_cmpxchg_4(__preempt_count, old, new) != old); |
38 | } |
39 | |
40 | /* |
41 | * must be macros to avoid header recursion hell |
42 | */ |
43 | #define init_task_preempt_count(p) do { } while (0) |
44 | |
45 | #define init_idle_preempt_count(p, cpu) do { \ |
46 | per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \ |
47 | } while (0) |
48 | |
49 | /* |
50 | * We fold the NEED_RESCHED bit into the preempt count such that |
51 | * preempt_enable() can decrement and test for needing to reschedule with a |
52 | * single instruction. |
53 | * |
54 | * We invert the actual bit, so that when the decrement hits 0 we know we both |
55 | * need to resched (the bit is cleared) and can resched (no preempt count). |
56 | */ |
57 | |
58 | static __always_inline void set_preempt_need_resched(void) |
59 | { |
60 | raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED); |
61 | } |
62 | |
63 | static __always_inline void clear_preempt_need_resched(void) |
64 | { |
65 | raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED); |
66 | } |
67 | |
68 | static __always_inline bool test_preempt_need_resched(void) |
69 | { |
70 | return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED); |
71 | } |
72 | |
73 | /* |
74 | * The various preempt_count add/sub methods |
75 | */ |
76 | |
77 | static __always_inline void __preempt_count_add(int val) |
78 | { |
79 | raw_cpu_add_4(__preempt_count, val); |
80 | } |
81 | |
82 | static __always_inline void __preempt_count_sub(int val) |
83 | { |
84 | raw_cpu_add_4(__preempt_count, -val); |
85 | } |
86 | |
87 | /* |
88 | * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule |
89 | * a decrement which hits zero means we have no preempt_count and should |
90 | * reschedule. |
91 | */ |
92 | static __always_inline bool __preempt_count_dec_and_test(void) |
93 | { |
94 | return GEN_UNARY_RMWcc("decl" , __preempt_count, e, __percpu_arg([var])); |
95 | } |
96 | |
97 | /* |
98 | * Returns true when we need to resched and can (barring IRQ state). |
99 | */ |
100 | static __always_inline bool should_resched(int preempt_offset) |
101 | { |
102 | return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset); |
103 | } |
104 | |
105 | #ifdef CONFIG_PREEMPT |
106 | extern asmlinkage void ___preempt_schedule(void); |
107 | # define __preempt_schedule() \ |
108 | asm volatile ("call ___preempt_schedule" : ASM_CALL_CONSTRAINT) |
109 | |
110 | extern asmlinkage void preempt_schedule(void); |
111 | extern asmlinkage void ___preempt_schedule_notrace(void); |
112 | # define __preempt_schedule_notrace() \ |
113 | asm volatile ("call ___preempt_schedule_notrace" : ASM_CALL_CONSTRAINT) |
114 | |
115 | extern asmlinkage void preempt_schedule_notrace(void); |
116 | #endif |
117 | |
118 | #endif /* __ASM_PREEMPT_H */ |
119 | |