| 1 | /* |
| 2 | * Generic barrier definitions, originally based on MN10300 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_acquire() - (Spin) wait for cond with ACQUIRE ordering |
| 225 | * @ptr: pointer to the variable to wait on |
| 226 | * @cond: boolean expression to wait for |
| 227 | * |
| 228 | * Equivalent to using smp_load_acquire() on the condition variable but employs |
| 229 | * the control dependency of the wait to reduce the barrier on many platforms. |
| 230 | * |
| 231 | * Due to C lacking lambda expressions we load the value of *ptr into a |
| 232 | * pre-named variable @VAL to be used in @cond. |
| 233 | */ |
| 234 | #ifndef smp_cond_load_acquire |
| 235 | #define smp_cond_load_acquire(ptr, cond_expr) ({ \ |
| 236 | typeof(ptr) __PTR = (ptr); \ |
| 237 | typeof(*ptr) VAL; \ |
| 238 | for (;;) { \ |
| 239 | VAL = READ_ONCE(*__PTR); \ |
| 240 | if (cond_expr) \ |
| 241 | break; \ |
| 242 | cpu_relax(); \ |
| 243 | } \ |
| 244 | smp_acquire__after_ctrl_dep(); \ |
| 245 | VAL; \ |
| 246 | }) |
| 247 | #endif |
| 248 | |
| 249 | #endif /* !__ASSEMBLY__ */ |
| 250 | #endif /* __ASM_GENERIC_BARRIER_H */ |