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b4d0d230 | 1 | /* SPDX-License-Identifier: GPL-2.0-or-later */ |
93ea02bb | 2 | /* |
739d875d | 3 | * Generic barrier definitions. |
885df91c DH |
4 | * |
5 | * It should be possible to use these on really simple architectures, | |
6 | * but it serves more as a starting point for new ports. | |
7 | * | |
8 | * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. | |
9 | * Written by David Howells (dhowells@redhat.com) | |
885df91c DH |
10 | */ |
11 | #ifndef __ASM_GENERIC_BARRIER_H | |
12 | #define __ASM_GENERIC_BARRIER_H | |
13 | ||
14 | #ifndef __ASSEMBLY__ | |
15 | ||
93ea02bb PZ |
16 | #include <linux/compiler.h> |
17 | ||
18 | #ifndef nop | |
19 | #define nop() asm volatile ("nop") | |
20 | #endif | |
885df91c DH |
21 | |
22 | /* | |
93ea02bb PZ |
23 | * Force strict CPU ordering. And yes, this is required on UP too when we're |
24 | * talking to devices. | |
885df91c | 25 | * |
93ea02bb | 26 | * Fall back to compiler barriers if nothing better is provided. |
885df91c DH |
27 | */ |
28 | ||
93ea02bb PZ |
29 | #ifndef mb |
30 | #define mb() barrier() | |
31 | #endif | |
32 | ||
33 | #ifndef rmb | |
885df91c | 34 | #define rmb() mb() |
93ea02bb PZ |
35 | #endif |
36 | ||
37 | #ifndef wmb | |
38 | #define wmb() mb() | |
39 | #endif | |
40 | ||
1077fa36 AD |
41 | #ifndef dma_rmb |
42 | #define dma_rmb() rmb() | |
43 | #endif | |
44 | ||
45 | #ifndef dma_wmb | |
46 | #define dma_wmb() wmb() | |
47 | #endif | |
48 | ||
93ea02bb PZ |
49 | #ifndef read_barrier_depends |
50 | #define read_barrier_depends() do { } while (0) | |
51 | #endif | |
885df91c | 52 | |
a9e4252a MT |
53 | #ifndef __smp_mb |
54 | #define __smp_mb() mb() | |
55 | #endif | |
56 | ||
57 | #ifndef __smp_rmb | |
58 | #define __smp_rmb() rmb() | |
59 | #endif | |
60 | ||
61 | #ifndef __smp_wmb | |
62 | #define __smp_wmb() wmb() | |
63 | #endif | |
64 | ||
65 | #ifndef __smp_read_barrier_depends | |
66 | #define __smp_read_barrier_depends() read_barrier_depends() | |
67 | #endif | |
68 | ||
885df91c | 69 | #ifdef CONFIG_SMP |
470c27e4 VG |
70 | |
71 | #ifndef smp_mb | |
a9e4252a | 72 | #define smp_mb() __smp_mb() |
470c27e4 VG |
73 | #endif |
74 | ||
75 | #ifndef smp_rmb | |
a9e4252a | 76 | #define smp_rmb() __smp_rmb() |
470c27e4 VG |
77 | #endif |
78 | ||
79 | #ifndef smp_wmb | |
a9e4252a | 80 | #define smp_wmb() __smp_wmb() |
470c27e4 VG |
81 | #endif |
82 | ||
83 | #ifndef smp_read_barrier_depends | |
a9e4252a | 84 | #define smp_read_barrier_depends() __smp_read_barrier_depends() |
470c27e4 VG |
85 | #endif |
86 | ||
0890a264 LT |
87 | #else /* !CONFIG_SMP */ |
88 | ||
470c27e4 | 89 | #ifndef smp_mb |
885df91c | 90 | #define smp_mb() barrier() |
470c27e4 VG |
91 | #endif |
92 | ||
93 | #ifndef smp_rmb | |
885df91c | 94 | #define smp_rmb() barrier() |
470c27e4 VG |
95 | #endif |
96 | ||
97 | #ifndef smp_wmb | |
885df91c | 98 | #define smp_wmb() barrier() |
470c27e4 VG |
99 | #endif |
100 | ||
101 | #ifndef smp_read_barrier_depends | |
93ea02bb | 102 | #define smp_read_barrier_depends() do { } while (0) |
885df91c DH |
103 | #endif |
104 | ||
0890a264 | 105 | #endif /* CONFIG_SMP */ |
470c27e4 | 106 | |
a9e4252a MT |
107 | #ifndef __smp_store_mb |
108 | #define __smp_store_mb(var, value) do { WRITE_ONCE(var, value); __smp_mb(); } while (0) | |
109 | #endif | |
110 | ||
111 | #ifndef __smp_mb__before_atomic | |
112 | #define __smp_mb__before_atomic() __smp_mb() | |
113 | #endif | |
114 | ||
115 | #ifndef __smp_mb__after_atomic | |
116 | #define __smp_mb__after_atomic() __smp_mb() | |
117 | #endif | |
118 | ||
119 | #ifndef __smp_store_release | |
120 | #define __smp_store_release(p, v) \ | |
121 | do { \ | |
122 | compiletime_assert_atomic_type(*p); \ | |
123 | __smp_mb(); \ | |
124 | WRITE_ONCE(*p, v); \ | |
125 | } while (0) | |
126 | #endif | |
127 | ||
128 | #ifndef __smp_load_acquire | |
129 | #define __smp_load_acquire(p) \ | |
130 | ({ \ | |
54988727 | 131 | __unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p); \ |
a9e4252a MT |
132 | compiletime_assert_atomic_type(*p); \ |
133 | __smp_mb(); \ | |
54988727 | 134 | (typeof(*p))___p1; \ |
a9e4252a MT |
135 | }) |
136 | #endif | |
137 | ||
138 | #ifdef CONFIG_SMP | |
139 | ||
140 | #ifndef smp_store_mb | |
141 | #define smp_store_mb(var, value) __smp_store_mb(var, value) | |
142 | #endif | |
143 | ||
144 | #ifndef smp_mb__before_atomic | |
145 | #define smp_mb__before_atomic() __smp_mb__before_atomic() | |
146 | #endif | |
147 | ||
148 | #ifndef smp_mb__after_atomic | |
149 | #define smp_mb__after_atomic() __smp_mb__after_atomic() | |
150 | #endif | |
151 | ||
152 | #ifndef smp_store_release | |
153 | #define smp_store_release(p, v) __smp_store_release(p, v) | |
154 | #endif | |
155 | ||
156 | #ifndef smp_load_acquire | |
157 | #define smp_load_acquire(p) __smp_load_acquire(p) | |
158 | #endif | |
159 | ||
160 | #else /* !CONFIG_SMP */ | |
161 | ||
b92b8b35 | 162 | #ifndef smp_store_mb |
a9e4252a | 163 | #define smp_store_mb(var, value) do { WRITE_ONCE(var, value); barrier(); } while (0) |
93ea02bb | 164 | #endif |
885df91c | 165 | |
febdbfe8 | 166 | #ifndef smp_mb__before_atomic |
a9e4252a | 167 | #define smp_mb__before_atomic() barrier() |
febdbfe8 PZ |
168 | #endif |
169 | ||
170 | #ifndef smp_mb__after_atomic | |
a9e4252a | 171 | #define smp_mb__after_atomic() barrier() |
febdbfe8 PZ |
172 | #endif |
173 | ||
57f7c037 | 174 | #ifndef smp_store_release |
47933ad4 PZ |
175 | #define smp_store_release(p, v) \ |
176 | do { \ | |
177 | compiletime_assert_atomic_type(*p); \ | |
a9e4252a | 178 | barrier(); \ |
76695af2 | 179 | WRITE_ONCE(*p, v); \ |
47933ad4 | 180 | } while (0) |
57f7c037 | 181 | #endif |
47933ad4 | 182 | |
57f7c037 | 183 | #ifndef smp_load_acquire |
47933ad4 PZ |
184 | #define smp_load_acquire(p) \ |
185 | ({ \ | |
54988727 | 186 | __unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p); \ |
47933ad4 | 187 | compiletime_assert_atomic_type(*p); \ |
a9e4252a | 188 | barrier(); \ |
54988727 | 189 | (typeof(*p))___p1; \ |
47933ad4 | 190 | }) |
57f7c037 | 191 | #endif |
47933ad4 | 192 | |
726328d9 | 193 | #endif /* CONFIG_SMP */ |
a9e4252a | 194 | |
6a65d263 MT |
195 | /* Barriers for virtual machine guests when talking to an SMP host */ |
196 | #define virt_mb() __smp_mb() | |
197 | #define virt_rmb() __smp_rmb() | |
198 | #define virt_wmb() __smp_wmb() | |
199 | #define virt_read_barrier_depends() __smp_read_barrier_depends() | |
200 | #define virt_store_mb(var, value) __smp_store_mb(var, value) | |
201 | #define virt_mb__before_atomic() __smp_mb__before_atomic() | |
202 | #define virt_mb__after_atomic() __smp_mb__after_atomic() | |
203 | #define virt_store_release(p, v) __smp_store_release(p, v) | |
204 | #define virt_load_acquire(p) __smp_load_acquire(p) | |
205 | ||
7cb45c0f PZ |
206 | /** |
207 | * smp_acquire__after_ctrl_dep() - Provide ACQUIRE ordering after a control dependency | |
208 | * | |
209 | * A control dependency provides a LOAD->STORE order, the additional RMB | |
210 | * provides LOAD->LOAD order, together they provide LOAD->{LOAD,STORE} order, | |
211 | * aka. (load)-ACQUIRE. | |
212 | * | |
213 | * Architectures that do not do load speculation can have this be barrier(). | |
214 | */ | |
215 | #ifndef smp_acquire__after_ctrl_dep | |
216 | #define smp_acquire__after_ctrl_dep() smp_rmb() | |
217 | #endif | |
218 | ||
219 | /** | |
fcfdfe30 | 220 | * smp_cond_load_relaxed() - (Spin) wait for cond with no ordering guarantees |
7cb45c0f PZ |
221 | * @ptr: pointer to the variable to wait on |
222 | * @cond: boolean expression to wait for | |
223 | * | |
fcfdfe30 | 224 | * Equivalent to using READ_ONCE() on the condition variable. |
7cb45c0f PZ |
225 | * |
226 | * Due to C lacking lambda expressions we load the value of *ptr into a | |
227 | * pre-named variable @VAL to be used in @cond. | |
228 | */ | |
fcfdfe30 WD |
229 | #ifndef smp_cond_load_relaxed |
230 | #define smp_cond_load_relaxed(ptr, cond_expr) ({ \ | |
7cb45c0f | 231 | typeof(ptr) __PTR = (ptr); \ |
54988727 | 232 | __unqual_scalar_typeof(*ptr) VAL; \ |
7cb45c0f PZ |
233 | for (;;) { \ |
234 | VAL = READ_ONCE(*__PTR); \ | |
235 | if (cond_expr) \ | |
236 | break; \ | |
237 | cpu_relax(); \ | |
238 | } \ | |
54988727 | 239 | (typeof(*ptr))VAL; \ |
7cb45c0f PZ |
240 | }) |
241 | #endif | |
242 | ||
fcfdfe30 WD |
243 | /** |
244 | * smp_cond_load_acquire() - (Spin) wait for cond with ACQUIRE ordering | |
245 | * @ptr: pointer to the variable to wait on | |
246 | * @cond: boolean expression to wait for | |
247 | * | |
248 | * Equivalent to using smp_load_acquire() on the condition variable but employs | |
249 | * the control dependency of the wait to reduce the barrier on many platforms. | |
250 | */ | |
251 | #ifndef smp_cond_load_acquire | |
252 | #define smp_cond_load_acquire(ptr, cond_expr) ({ \ | |
54988727 | 253 | __unqual_scalar_typeof(*ptr) _val; \ |
fcfdfe30 WD |
254 | _val = smp_cond_load_relaxed(ptr, cond_expr); \ |
255 | smp_acquire__after_ctrl_dep(); \ | |
54988727 | 256 | (typeof(*ptr))_val; \ |
fcfdfe30 WD |
257 | }) |
258 | #endif | |
259 | ||
885df91c DH |
260 | #endif /* !__ASSEMBLY__ */ |
261 | #endif /* __ASM_GENERIC_BARRIER_H */ |