| 1 | #ifndef QEMU_RCU_QUEUE_H |
| 2 | #define QEMU_RCU_QUEUE_H |
| 3 | |
| 4 | /* |
| 5 | * rcu_queue.h |
| 6 | * |
| 7 | * RCU-friendly versions of the queue.h primitives. |
| 8 | * |
| 9 | * This library is free software; you can redistribute it and/or |
| 10 | * modify it under the terms of the GNU Lesser General Public |
| 11 | * License as published by the Free Software Foundation; either |
| 12 | * version 2.1 of the License, or (at your option) any later version. |
| 13 | * |
| 14 | * This library is distributed in the hope that it will be useful, |
| 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 17 | * Lesser General Public License for more details. |
| 18 | * |
| 19 | * You should have received a copy of the GNU Lesser General Public |
| 20 | * License along with this library; if not, see |
| 21 | * <https://www.gnu.org/licenses/>. |
| 22 | * |
| 23 | * Copyright (c) 2013 Mike D. Day, IBM Corporation. |
| 24 | * |
| 25 | * IBM's contributions to this file may be relicensed under LGPLv2 or later. |
| 26 | */ |
| 27 | |
| 28 | #include "qemu/queue.h" |
| 29 | #include "qemu/atomic.h" |
| 30 | |
| 31 | /* |
| 32 | * List access methods. |
| 33 | */ |
| 34 | #define QLIST_EMPTY_RCU(head) (qatomic_read(&(head)->lh_first) == NULL) |
| 35 | #define QLIST_FIRST_RCU(head) (qatomic_rcu_read(&(head)->lh_first)) |
| 36 | #define QLIST_NEXT_RCU(elm, field) (qatomic_rcu_read(&(elm)->field.le_next)) |
| 37 | |
| 38 | /* |
| 39 | * List functions. |
| 40 | */ |
| 41 | |
| 42 | |
| 43 | /* |
| 44 | * The difference between qatomic_read/set and qatomic_rcu_read/set |
| 45 | * is in the including of a read/write memory barrier to the volatile |
| 46 | * access. atomic_rcu_* macros include the memory barrier, the |
| 47 | * plain atomic macros do not. Therefore, it should be correct to |
| 48 | * issue a series of reads or writes to the same element using only |
| 49 | * the atomic_* macro, until the last read or write, which should be |
| 50 | * atomic_rcu_* to introduce a read or write memory barrier as |
| 51 | * appropriate. |
| 52 | */ |
| 53 | |
| 54 | /* Upon publication of the listelm->next value, list readers |
| 55 | * will see the new node when following next pointers from |
| 56 | * antecedent nodes, but may not see the new node when following |
| 57 | * prev pointers from subsequent nodes until after the RCU grace |
| 58 | * period expires. |
| 59 | * see linux/include/rculist.h __list_add_rcu(new, prev, next) |
| 60 | */ |
| 61 | #define QLIST_INSERT_AFTER_RCU(listelm, elm, field) do { \ |
| 62 | (elm)->field.le_next = (listelm)->field.le_next; \ |
| 63 | (elm)->field.le_prev = &(listelm)->field.le_next; \ |
| 64 | qatomic_rcu_set(&(listelm)->field.le_next, (elm)); \ |
| 65 | if ((elm)->field.le_next != NULL) { \ |
| 66 | (elm)->field.le_next->field.le_prev = \ |
| 67 | &(elm)->field.le_next; \ |
| 68 | } \ |
| 69 | } while (/*CONSTCOND*/0) |
| 70 | |
| 71 | /* Upon publication of the listelm->prev->next value, list |
| 72 | * readers will see the new element when following prev pointers |
| 73 | * from subsequent elements, but may not see the new element |
| 74 | * when following next pointers from antecedent elements |
| 75 | * until after the RCU grace period expires. |
| 76 | */ |
| 77 | #define QLIST_INSERT_BEFORE_RCU(listelm, elm, field) do { \ |
| 78 | (elm)->field.le_prev = (listelm)->field.le_prev; \ |
| 79 | (elm)->field.le_next = (listelm); \ |
| 80 | qatomic_rcu_set((listelm)->field.le_prev, (elm)); \ |
| 81 | (listelm)->field.le_prev = &(elm)->field.le_next; \ |
| 82 | } while (/*CONSTCOND*/0) |
| 83 | |
| 84 | /* Upon publication of the head->first value, list readers |
| 85 | * will see the new element when following the head, but may |
| 86 | * not see the new element when following prev pointers from |
| 87 | * subsequent elements until after the RCU grace period has |
| 88 | * expired. |
| 89 | */ |
| 90 | #define QLIST_INSERT_HEAD_RCU(head, elm, field) do { \ |
| 91 | (elm)->field.le_prev = &(head)->lh_first; \ |
| 92 | (elm)->field.le_next = (head)->lh_first; \ |
| 93 | qatomic_rcu_set((&(head)->lh_first), (elm)); \ |
| 94 | if ((elm)->field.le_next != NULL) { \ |
| 95 | (elm)->field.le_next->field.le_prev = \ |
| 96 | &(elm)->field.le_next; \ |
| 97 | } \ |
| 98 | } while (/*CONSTCOND*/0) |
| 99 | |
| 100 | |
| 101 | /* prior to publication of the elm->prev->next value, some list |
| 102 | * readers may still see the removed element when following |
| 103 | * the antecedent's next pointer. |
| 104 | */ |
| 105 | #define QLIST_REMOVE_RCU(elm, field) do { \ |
| 106 | if ((elm)->field.le_next != NULL) { \ |
| 107 | (elm)->field.le_next->field.le_prev = \ |
| 108 | (elm)->field.le_prev; \ |
| 109 | } \ |
| 110 | qatomic_set((elm)->field.le_prev, (elm)->field.le_next); \ |
| 111 | } while (/*CONSTCOND*/0) |
| 112 | |
| 113 | /* List traversal must occur within an RCU critical section. */ |
| 114 | #define QLIST_FOREACH_RCU(var, head, field) \ |
| 115 | for ((var) = qatomic_rcu_read(&(head)->lh_first); \ |
| 116 | (var); \ |
| 117 | (var) = qatomic_rcu_read(&(var)->field.le_next)) |
| 118 | |
| 119 | /* List traversal must occur within an RCU critical section. */ |
| 120 | #define QLIST_FOREACH_SAFE_RCU(var, head, field, next_var) \ |
| 121 | for ((var) = (qatomic_rcu_read(&(head)->lh_first)); \ |
| 122 | (var) && \ |
| 123 | ((next_var) = qatomic_rcu_read(&(var)->field.le_next), 1); \ |
| 124 | (var) = (next_var)) |
| 125 | |
| 126 | /* |
| 127 | * RCU simple queue |
| 128 | */ |
| 129 | |
| 130 | /* Simple queue access methods */ |
| 131 | #define QSIMPLEQ_EMPTY_RCU(head) \ |
| 132 | (qatomic_read(&(head)->sqh_first) == NULL) |
| 133 | #define QSIMPLEQ_FIRST_RCU(head) qatomic_rcu_read(&(head)->sqh_first) |
| 134 | #define QSIMPLEQ_NEXT_RCU(elm, field) qatomic_rcu_read(&(elm)->field.sqe_next) |
| 135 | |
| 136 | /* Simple queue functions */ |
| 137 | #define QSIMPLEQ_INSERT_HEAD_RCU(head, elm, field) do { \ |
| 138 | (elm)->field.sqe_next = (head)->sqh_first; \ |
| 139 | if ((elm)->field.sqe_next == NULL) { \ |
| 140 | (head)->sqh_last = &(elm)->field.sqe_next; \ |
| 141 | } \ |
| 142 | qatomic_rcu_set(&(head)->sqh_first, (elm)); \ |
| 143 | } while (/*CONSTCOND*/0) |
| 144 | |
| 145 | #define QSIMPLEQ_INSERT_TAIL_RCU(head, elm, field) do { \ |
| 146 | (elm)->field.sqe_next = NULL; \ |
| 147 | qatomic_rcu_set((head)->sqh_last, (elm)); \ |
| 148 | (head)->sqh_last = &(elm)->field.sqe_next; \ |
| 149 | } while (/*CONSTCOND*/0) |
| 150 | |
| 151 | #define QSIMPLEQ_INSERT_AFTER_RCU(head, listelm, elm, field) do { \ |
| 152 | (elm)->field.sqe_next = (listelm)->field.sqe_next; \ |
| 153 | if ((elm)->field.sqe_next == NULL) { \ |
| 154 | (head)->sqh_last = &(elm)->field.sqe_next; \ |
| 155 | } \ |
| 156 | qatomic_rcu_set(&(listelm)->field.sqe_next, (elm)); \ |
| 157 | } while (/*CONSTCOND*/0) |
| 158 | |
| 159 | #define QSIMPLEQ_REMOVE_HEAD_RCU(head, field) do { \ |
| 160 | qatomic_set(&(head)->sqh_first, (head)->sqh_first->field.sqe_next);\ |
| 161 | if ((head)->sqh_first == NULL) { \ |
| 162 | (head)->sqh_last = &(head)->sqh_first; \ |
| 163 | } \ |
| 164 | } while (/*CONSTCOND*/0) |
| 165 | |
| 166 | #define QSIMPLEQ_REMOVE_RCU(head, elm, type, field) do { \ |
| 167 | if ((head)->sqh_first == (elm)) { \ |
| 168 | QSIMPLEQ_REMOVE_HEAD_RCU((head), field); \ |
| 169 | } else { \ |
| 170 | struct type *curr = (head)->sqh_first; \ |
| 171 | while (curr->field.sqe_next != (elm)) { \ |
| 172 | curr = curr->field.sqe_next; \ |
| 173 | } \ |
| 174 | qatomic_set(&curr->field.sqe_next, \ |
| 175 | curr->field.sqe_next->field.sqe_next); \ |
| 176 | if (curr->field.sqe_next == NULL) { \ |
| 177 | (head)->sqh_last = &(curr)->field.sqe_next; \ |
| 178 | } \ |
| 179 | } \ |
| 180 | } while (/*CONSTCOND*/0) |
| 181 | |
| 182 | #define QSIMPLEQ_FOREACH_RCU(var, head, field) \ |
| 183 | for ((var) = qatomic_rcu_read(&(head)->sqh_first); \ |
| 184 | (var); \ |
| 185 | (var) = qatomic_rcu_read(&(var)->field.sqe_next)) |
| 186 | |
| 187 | #define QSIMPLEQ_FOREACH_SAFE_RCU(var, head, field, next) \ |
| 188 | for ((var) = qatomic_rcu_read(&(head)->sqh_first); \ |
| 189 | (var) && ((next) = qatomic_rcu_read(&(var)->field.sqe_next), 1);\ |
| 190 | (var) = (next)) |
| 191 | |
| 192 | /* |
| 193 | * RCU tail queue |
| 194 | */ |
| 195 | |
| 196 | /* Tail queue access methods */ |
| 197 | #define QTAILQ_EMPTY_RCU(head) (qatomic_read(&(head)->tqh_first) == NULL) |
| 198 | #define QTAILQ_FIRST_RCU(head) qatomic_rcu_read(&(head)->tqh_first) |
| 199 | #define QTAILQ_NEXT_RCU(elm, field) qatomic_rcu_read(&(elm)->field.tqe_next) |
| 200 | |
| 201 | /* Tail queue functions */ |
| 202 | #define QTAILQ_INSERT_HEAD_RCU(head, elm, field) do { \ |
| 203 | (elm)->field.tqe_next = (head)->tqh_first; \ |
| 204 | if ((elm)->field.tqe_next != NULL) { \ |
| 205 | (head)->tqh_first->field.tqe_circ.tql_prev = \ |
| 206 | &(elm)->field.tqe_circ; \ |
| 207 | } else { \ |
| 208 | (head)->tqh_circ.tql_prev = &(elm)->field.tqe_circ; \ |
| 209 | } \ |
| 210 | qatomic_rcu_set(&(head)->tqh_first, (elm)); \ |
| 211 | (elm)->field.tqe_circ.tql_prev = &(head)->tqh_circ; \ |
| 212 | } while (/*CONSTCOND*/0) |
| 213 | |
| 214 | #define QTAILQ_INSERT_TAIL_RCU(head, elm, field) do { \ |
| 215 | (elm)->field.tqe_next = NULL; \ |
| 216 | (elm)->field.tqe_circ.tql_prev = (head)->tqh_circ.tql_prev; \ |
| 217 | qatomic_rcu_set(&(head)->tqh_circ.tql_prev->tql_next, (elm)); \ |
| 218 | (head)->tqh_circ.tql_prev = &(elm)->field.tqe_circ; \ |
| 219 | } while (/*CONSTCOND*/0) |
| 220 | |
| 221 | #define QTAILQ_INSERT_AFTER_RCU(head, listelm, elm, field) do { \ |
| 222 | (elm)->field.tqe_next = (listelm)->field.tqe_next; \ |
| 223 | if ((elm)->field.tqe_next != NULL) { \ |
| 224 | (elm)->field.tqe_next->field.tqe_circ.tql_prev = \ |
| 225 | &(elm)->field.tqe_circ; \ |
| 226 | } else { \ |
| 227 | (head)->tqh_circ.tql_prev = &(elm)->field.tqe_circ; \ |
| 228 | } \ |
| 229 | qatomic_rcu_set(&(listelm)->field.tqe_next, (elm)); \ |
| 230 | (elm)->field.tqe_circ.tql_prev = &(listelm)->field.tqe_circ; \ |
| 231 | } while (/*CONSTCOND*/0) |
| 232 | |
| 233 | #define QTAILQ_INSERT_BEFORE_RCU(listelm, elm, field) do { \ |
| 234 | (elm)->field.tqe_circ.tql_prev = (listelm)->field.tqe_circ.tql_prev; \ |
| 235 | (elm)->field.tqe_next = (listelm); \ |
| 236 | qatomic_rcu_set(&(listelm)->field.tqe_circ.tql_prev->tql_next, (elm));\ |
| 237 | (listelm)->field.tqe_circ.tql_prev = &(elm)->field.tqe_circ; \ |
| 238 | } while (/*CONSTCOND*/0) |
| 239 | |
| 240 | #define QTAILQ_REMOVE_RCU(head, elm, field) do { \ |
| 241 | if (((elm)->field.tqe_next) != NULL) { \ |
| 242 | (elm)->field.tqe_next->field.tqe_circ.tql_prev = \ |
| 243 | (elm)->field.tqe_circ.tql_prev; \ |
| 244 | } else { \ |
| 245 | (head)->tqh_circ.tql_prev = (elm)->field.tqe_circ.tql_prev; \ |
| 246 | } \ |
| 247 | qatomic_set(&(elm)->field.tqe_circ.tql_prev->tql_next, \ |
| 248 | (elm)->field.tqe_next); \ |
| 249 | (elm)->field.tqe_circ.tql_prev = NULL; \ |
| 250 | } while (/*CONSTCOND*/0) |
| 251 | |
| 252 | #define QTAILQ_FOREACH_RCU(var, head, field) \ |
| 253 | for ((var) = qatomic_rcu_read(&(head)->tqh_first); \ |
| 254 | (var); \ |
| 255 | (var) = qatomic_rcu_read(&(var)->field.tqe_next)) |
| 256 | |
| 257 | #define QTAILQ_FOREACH_SAFE_RCU(var, head, field, next) \ |
| 258 | for ((var) = qatomic_rcu_read(&(head)->tqh_first); \ |
| 259 | (var) && ((next) = qatomic_rcu_read(&(var)->field.tqe_next), 1);\ |
| 260 | (var) = (next)) |
| 261 | |
| 262 | /* |
| 263 | * RCU singly-linked list |
| 264 | */ |
| 265 | |
| 266 | /* Singly-linked list access methods */ |
| 267 | #define QSLIST_EMPTY_RCU(head) (qatomic_read(&(head)->slh_first) == NULL) |
| 268 | #define QSLIST_FIRST_RCU(head) qatomic_rcu_read(&(head)->slh_first) |
| 269 | #define QSLIST_NEXT_RCU(elm, field) qatomic_rcu_read(&(elm)->field.sle_next) |
| 270 | |
| 271 | /* Singly-linked list functions */ |
| 272 | #define QSLIST_INSERT_HEAD_RCU(head, elm, field) do { \ |
| 273 | (elm)->field.sle_next = (head)->slh_first; \ |
| 274 | qatomic_rcu_set(&(head)->slh_first, (elm)); \ |
| 275 | } while (/*CONSTCOND*/0) |
| 276 | |
| 277 | #define QSLIST_INSERT_AFTER_RCU(head, listelm, elm, field) do { \ |
| 278 | (elm)->field.sle_next = (listelm)->field.sle_next; \ |
| 279 | qatomic_rcu_set(&(listelm)->field.sle_next, (elm)); \ |
| 280 | } while (/*CONSTCOND*/0) |
| 281 | |
| 282 | #define QSLIST_REMOVE_HEAD_RCU(head, field) do { \ |
| 283 | qatomic_set(&(head)->slh_first, (head)->slh_first->field.sle_next);\ |
| 284 | } while (/*CONSTCOND*/0) |
| 285 | |
| 286 | #define QSLIST_REMOVE_RCU(head, elm, type, field) do { \ |
| 287 | if ((head)->slh_first == (elm)) { \ |
| 288 | QSLIST_REMOVE_HEAD_RCU((head), field); \ |
| 289 | } else { \ |
| 290 | struct type *curr = (head)->slh_first; \ |
| 291 | while (curr->field.sle_next != (elm)) { \ |
| 292 | curr = curr->field.sle_next; \ |
| 293 | } \ |
| 294 | qatomic_set(&curr->field.sle_next, \ |
| 295 | curr->field.sle_next->field.sle_next); \ |
| 296 | } \ |
| 297 | } while (/*CONSTCOND*/0) |
| 298 | |
| 299 | #define QSLIST_FOREACH_RCU(var, head, field) \ |
| 300 | for ((var) = qatomic_rcu_read(&(head)->slh_first); \ |
| 301 | (var); \ |
| 302 | (var) = qatomic_rcu_read(&(var)->field.sle_next)) |
| 303 | |
| 304 | #define QSLIST_FOREACH_SAFE_RCU(var, head, field, next) \ |
| 305 | for ((var) = qatomic_rcu_read(&(head)->slh_first); \ |
| 306 | (var) && ((next) = qatomic_rcu_read(&(var)->field.sle_next), 1); \ |
| 307 | (var) = (next)) |
| 308 | |
| 309 | #endif /* QEMU_RCU_QUEUE_H */ |