1 | /* |
2 | * Generic barrier definitions. |
3 | * |
4 | * It should be possible to use these on really simple architectures, |
5 | * but it serves more as a starting point for new ports. |
6 | * |
7 | * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. |
8 | * Written by David Howells (dhowells@redhat.com) |
9 | * |
10 | * This program is free software; you can redistribute it and/or |
11 | * modify it under the terms of the GNU General Public Licence |
12 | * as published by the Free Software Foundation; either version |
13 | * 2 of the Licence, or (at your option) any later version. |
14 | */ |
15 | #ifndef __ASM_GENERIC_BARRIER_H |
16 | #define __ASM_GENERIC_BARRIER_H |
17 | |
18 | #ifndef __ASSEMBLY__ |
19 | |
20 | #include <linux/compiler.h> |
21 | |
22 | #ifndef nop |
23 | #define nop() asm volatile ("nop") |
24 | #endif |
25 | |
26 | /* |
27 | * Force strict CPU ordering. And yes, this is required on UP too when we're |
28 | * talking to devices. |
29 | * |
30 | * Fall back to compiler barriers if nothing better is provided. |
31 | */ |
32 | |
33 | #ifndef mb |
34 | #define mb() barrier() |
35 | #endif |
36 | |
37 | #ifndef rmb |
38 | #define rmb() mb() |
39 | #endif |
40 | |
41 | #ifndef wmb |
42 | #define wmb() mb() |
43 | #endif |
44 | |
45 | #ifndef dma_rmb |
46 | #define dma_rmb() rmb() |
47 | #endif |
48 | |
49 | #ifndef dma_wmb |
50 | #define dma_wmb() wmb() |
51 | #endif |
52 | |
53 | #ifndef read_barrier_depends |
54 | #define read_barrier_depends() do { } while (0) |
55 | #endif |
56 | |
57 | #ifndef __smp_mb |
58 | #define __smp_mb() mb() |
59 | #endif |
60 | |
61 | #ifndef __smp_rmb |
62 | #define __smp_rmb() rmb() |
63 | #endif |
64 | |
65 | #ifndef __smp_wmb |
66 | #define __smp_wmb() wmb() |
67 | #endif |
68 | |
69 | #ifndef __smp_read_barrier_depends |
70 | #define __smp_read_barrier_depends() read_barrier_depends() |
71 | #endif |
72 | |
73 | #ifdef CONFIG_SMP |
74 | |
75 | #ifndef smp_mb |
76 | #define smp_mb() __smp_mb() |
77 | #endif |
78 | |
79 | #ifndef smp_rmb |
80 | #define smp_rmb() __smp_rmb() |
81 | #endif |
82 | |
83 | #ifndef smp_wmb |
84 | #define smp_wmb() __smp_wmb() |
85 | #endif |
86 | |
87 | #ifndef smp_read_barrier_depends |
88 | #define smp_read_barrier_depends() __smp_read_barrier_depends() |
89 | #endif |
90 | |
91 | #else /* !CONFIG_SMP */ |
92 | |
93 | #ifndef smp_mb |
94 | #define smp_mb() barrier() |
95 | #endif |
96 | |
97 | #ifndef smp_rmb |
98 | #define smp_rmb() barrier() |
99 | #endif |
100 | |
101 | #ifndef smp_wmb |
102 | #define smp_wmb() barrier() |
103 | #endif |
104 | |
105 | #ifndef smp_read_barrier_depends |
106 | #define smp_read_barrier_depends() do { } while (0) |
107 | #endif |
108 | |
109 | #endif /* CONFIG_SMP */ |
110 | |
111 | #ifndef __smp_store_mb |
112 | #define __smp_store_mb(var, value) do { WRITE_ONCE(var, value); __smp_mb(); } while (0) |
113 | #endif |
114 | |
115 | #ifndef __smp_mb__before_atomic |
116 | #define __smp_mb__before_atomic() __smp_mb() |
117 | #endif |
118 | |
119 | #ifndef __smp_mb__after_atomic |
120 | #define __smp_mb__after_atomic() __smp_mb() |
121 | #endif |
122 | |
123 | #ifndef __smp_store_release |
124 | #define __smp_store_release(p, v) \ |
125 | do { \ |
126 | compiletime_assert_atomic_type(*p); \ |
127 | __smp_mb(); \ |
128 | WRITE_ONCE(*p, v); \ |
129 | } while (0) |
130 | #endif |
131 | |
132 | #ifndef __smp_load_acquire |
133 | #define __smp_load_acquire(p) \ |
134 | ({ \ |
135 | typeof(*p) ___p1 = READ_ONCE(*p); \ |
136 | compiletime_assert_atomic_type(*p); \ |
137 | __smp_mb(); \ |
138 | ___p1; \ |
139 | }) |
140 | #endif |
141 | |
142 | #ifdef CONFIG_SMP |
143 | |
144 | #ifndef smp_store_mb |
145 | #define smp_store_mb(var, value) __smp_store_mb(var, value) |
146 | #endif |
147 | |
148 | #ifndef smp_mb__before_atomic |
149 | #define smp_mb__before_atomic() __smp_mb__before_atomic() |
150 | #endif |
151 | |
152 | #ifndef smp_mb__after_atomic |
153 | #define smp_mb__after_atomic() __smp_mb__after_atomic() |
154 | #endif |
155 | |
156 | #ifndef smp_store_release |
157 | #define smp_store_release(p, v) __smp_store_release(p, v) |
158 | #endif |
159 | |
160 | #ifndef smp_load_acquire |
161 | #define smp_load_acquire(p) __smp_load_acquire(p) |
162 | #endif |
163 | |
164 | #else /* !CONFIG_SMP */ |
165 | |
166 | #ifndef smp_store_mb |
167 | #define smp_store_mb(var, value) do { WRITE_ONCE(var, value); barrier(); } while (0) |
168 | #endif |
169 | |
170 | #ifndef smp_mb__before_atomic |
171 | #define smp_mb__before_atomic() barrier() |
172 | #endif |
173 | |
174 | #ifndef smp_mb__after_atomic |
175 | #define smp_mb__after_atomic() barrier() |
176 | #endif |
177 | |
178 | #ifndef smp_store_release |
179 | #define smp_store_release(p, v) \ |
180 | do { \ |
181 | compiletime_assert_atomic_type(*p); \ |
182 | barrier(); \ |
183 | WRITE_ONCE(*p, v); \ |
184 | } while (0) |
185 | #endif |
186 | |
187 | #ifndef smp_load_acquire |
188 | #define smp_load_acquire(p) \ |
189 | ({ \ |
190 | typeof(*p) ___p1 = READ_ONCE(*p); \ |
191 | compiletime_assert_atomic_type(*p); \ |
192 | barrier(); \ |
193 | ___p1; \ |
194 | }) |
195 | #endif |
196 | |
197 | #endif /* CONFIG_SMP */ |
198 | |
199 | /* Barriers for virtual machine guests when talking to an SMP host */ |
200 | #define virt_mb() __smp_mb() |
201 | #define virt_rmb() __smp_rmb() |
202 | #define virt_wmb() __smp_wmb() |
203 | #define virt_read_barrier_depends() __smp_read_barrier_depends() |
204 | #define virt_store_mb(var, value) __smp_store_mb(var, value) |
205 | #define virt_mb__before_atomic() __smp_mb__before_atomic() |
206 | #define virt_mb__after_atomic() __smp_mb__after_atomic() |
207 | #define virt_store_release(p, v) __smp_store_release(p, v) |
208 | #define virt_load_acquire(p) __smp_load_acquire(p) |
209 | |
210 | /** |
211 | * smp_acquire__after_ctrl_dep() - Provide ACQUIRE ordering after a control dependency |
212 | * |
213 | * A control dependency provides a LOAD->STORE order, the additional RMB |
214 | * provides LOAD->LOAD order, together they provide LOAD->{LOAD,STORE} order, |
215 | * aka. (load)-ACQUIRE. |
216 | * |
217 | * Architectures that do not do load speculation can have this be barrier(). |
218 | */ |
219 | #ifndef smp_acquire__after_ctrl_dep |
220 | #define smp_acquire__after_ctrl_dep() smp_rmb() |
221 | #endif |
222 | |
223 | /** |
224 | * smp_cond_load_relaxed() - (Spin) wait for cond with no ordering guarantees |
225 | * @ptr: pointer to the variable to wait on |
226 | * @cond: boolean expression to wait for |
227 | * |
228 | * Equivalent to using READ_ONCE() on the condition variable. |
229 | * |
230 | * Due to C lacking lambda expressions we load the value of *ptr into a |
231 | * pre-named variable @VAL to be used in @cond. |
232 | */ |
233 | #ifndef smp_cond_load_relaxed |
234 | #define smp_cond_load_relaxed(ptr, cond_expr) ({ \ |
235 | typeof(ptr) __PTR = (ptr); \ |
236 | typeof(*ptr) VAL; \ |
237 | for (;;) { \ |
238 | VAL = READ_ONCE(*__PTR); \ |
239 | if (cond_expr) \ |
240 | break; \ |
241 | cpu_relax(); \ |
242 | } \ |
243 | VAL; \ |
244 | }) |
245 | #endif |
246 | |
247 | /** |
248 | * smp_cond_load_acquire() - (Spin) wait for cond with ACQUIRE ordering |
249 | * @ptr: pointer to the variable to wait on |
250 | * @cond: boolean expression to wait for |
251 | * |
252 | * Equivalent to using smp_load_acquire() on the condition variable but employs |
253 | * the control dependency of the wait to reduce the barrier on many platforms. |
254 | */ |
255 | #ifndef smp_cond_load_acquire |
256 | #define smp_cond_load_acquire(ptr, cond_expr) ({ \ |
257 | typeof(*ptr) _val; \ |
258 | _val = smp_cond_load_relaxed(ptr, cond_expr); \ |
259 | smp_acquire__after_ctrl_dep(); \ |
260 | _val; \ |
261 | }) |
262 | #endif |
263 | |
264 | #endif /* !__ASSEMBLY__ */ |
265 | #endif /* __ASM_GENERIC_BARRIER_H */ |
266 | |