include/qemu/rcu_queue.h

   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, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  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 #ifdef __cplusplus
  32 extern "C" {
  33 #endif
  34
  35
  36 /*
  37  * List access methods.
  38  */
  39 #define QLIST_EMPTY_RCU(head) (qatomic_read(&(head)->lh_first) == NULL)
  40 #define QLIST_FIRST_RCU(head) (qatomic_rcu_read(&(head)->lh_first))
  41 #define QLIST_NEXT_RCU(elm, field) (qatomic_rcu_read(&(elm)->field.le_next))
  42
  43 /*
  44  * List functions.
  45  */
  46
  47
  48 /*
  49  *  The difference between qatomic_read/set and qatomic_rcu_read/set
  50  *  is in the including of a read/write memory barrier to the volatile
  51  *  access. atomic_rcu_* macros include the memory barrier, the
  52  *  plain atomic macros do not. Therefore, it should be correct to
  53  *  issue a series of reads or writes to the same element using only
  54  *  the atomic_* macro, until the last read or write, which should be
  55  *  atomic_rcu_* to introduce a read or write memory barrier as
  56  *  appropriate.
  57  */
  58
  59 /* Upon publication of the listelm->next value, list readers
  60  * will see the new node when following next pointers from
  61  * antecedent nodes, but may not see the new node when following
  62  * prev pointers from subsequent nodes until after the RCU grace
  63  * period expires.
  64  * see linux/include/rculist.h __list_add_rcu(new, prev, next)
  65  */
  66 #define QLIST_INSERT_AFTER_RCU(listelm, elm, field) do {    \
  67     (elm)->field.le_next = (listelm)->field.le_next;        \
  68     (elm)->field.le_prev = &(listelm)->field.le_next;       \
  69     qatomic_rcu_set(&(listelm)->field.le_next, (elm));      \
  70     if ((elm)->field.le_next != NULL) {                     \
  71        (elm)->field.le_next->field.le_prev =                \
  72         &(elm)->field.le_next;                              \
  73     }                                                       \
  74 } while (/*CONSTCOND*/0)
  75
  76 /* Upon publication of the listelm->prev->next value, list
  77  * readers will see the new element when following prev pointers
  78  * from subsequent elements, but may not see the new element
  79  * when following next pointers from antecedent elements
  80  * until after the RCU grace period expires.
  81  */
  82 #define QLIST_INSERT_BEFORE_RCU(listelm, elm, field) do {   \
  83     (elm)->field.le_prev = (listelm)->field.le_prev;        \
  84     (elm)->field.le_next = (listelm);                       \
  85     qatomic_rcu_set((listelm)->field.le_prev, (elm));       \
  86     (listelm)->field.le_prev = &(elm)->field.le_next;       \
  87 } while (/*CONSTCOND*/0)
  88
  89 /* Upon publication of the head->first value, list readers
  90  * will see the new element when following the head, but may
  91  * not see the new element when following prev pointers from
  92  * subsequent elements until after the RCU grace period has
  93  * expired.
  94  */
  95 #define QLIST_INSERT_HEAD_RCU(head, elm, field) do {    \
  96     (elm)->field.le_prev = &(head)->lh_first;           \
  97     (elm)->field.le_next = (head)->lh_first;            \
  98     qatomic_rcu_set((&(head)->lh_first), (elm));        \
  99     if ((elm)->field.le_next != NULL) {                 \
 100        (elm)->field.le_next->field.le_prev =            \
 101         &(elm)->field.le_next;                          \
 102     }                                                   \
 103 } while (/*CONSTCOND*/0)
 104
 105
 106 /* prior to publication of the elm->prev->next value, some list
 107  * readers may still see the removed element when following
 108  * the antecedent's next pointer.
 109  */
 110 #define QLIST_REMOVE_RCU(elm, field) do {           \
 111     if ((elm)->field.le_next != NULL) {             \
 112        (elm)->field.le_next->field.le_prev =        \
 113         (elm)->field.le_prev;                       \
 114     }                                               \
 115     qatomic_set((elm)->field.le_prev, (elm)->field.le_next); \
 116 } while (/*CONSTCOND*/0)
 117
 118 /* List traversal must occur within an RCU critical section.  */
 119 #define QLIST_FOREACH_RCU(var, head, field)                 \
 120         for ((var) = qatomic_rcu_read(&(head)->lh_first);   \
 121                 (var);                                      \
 122                 (var) = qatomic_rcu_read(&(var)->field.le_next))
 123
 124 /* List traversal must occur within an RCU critical section.  */
 125 #define QLIST_FOREACH_SAFE_RCU(var, head, field, next_var)           \
 126     for ((var) = (qatomic_rcu_read(&(head)->lh_first));              \
 127       (var) &&                                                       \
 128           ((next_var) = qatomic_rcu_read(&(var)->field.le_next), 1); \
 129            (var) = (next_var))
 130
 131 /*
 132  * RCU simple queue
 133  */
 134
 135 /* Simple queue access methods */
 136 #define QSIMPLEQ_EMPTY_RCU(head) \
 137     (qatomic_read(&(head)->sqh_first) == NULL)
 138 #define QSIMPLEQ_FIRST_RCU(head)       qatomic_rcu_read(&(head)->sqh_first)
 139 #define QSIMPLEQ_NEXT_RCU(elm, field)  qatomic_rcu_read(&(elm)->field.sqe_next)
 140
 141 /* Simple queue functions */
 142 #define QSIMPLEQ_INSERT_HEAD_RCU(head, elm, field) do {         \
 143     (elm)->field.sqe_next = (head)->sqh_first;                  \
 144     if ((elm)->field.sqe_next == NULL) {                        \
 145         (head)->sqh_last = &(elm)->field.sqe_next;              \
 146     }                                                           \
 147     qatomic_rcu_set(&(head)->sqh_first, (elm));                 \
 148 } while (/*CONSTCOND*/0)
 149
 150 #define QSIMPLEQ_INSERT_TAIL_RCU(head, elm, field) do {    \
 151     (elm)->field.sqe_next = NULL;                          \
 152     qatomic_rcu_set((head)->sqh_last, (elm));              \
 153     (head)->sqh_last = &(elm)->field.sqe_next;             \
 154 } while (/*CONSTCOND*/0)
 155
 156 #define QSIMPLEQ_INSERT_AFTER_RCU(head, listelm, elm, field) do {       \
 157     (elm)->field.sqe_next = (listelm)->field.sqe_next;                  \
 158     if ((elm)->field.sqe_next == NULL) {                                \
 159         (head)->sqh_last = &(elm)->field.sqe_next;                      \
 160     }                                                                   \
 161     qatomic_rcu_set(&(listelm)->field.sqe_next, (elm));                 \
 162 } while (/*CONSTCOND*/0)
 163
 164 #define QSIMPLEQ_REMOVE_HEAD_RCU(head, field) do {                     \
 165     qatomic_set(&(head)->sqh_first, (head)->sqh_first->field.sqe_next);\
 166     if ((head)->sqh_first == NULL) {                                   \
 167         (head)->sqh_last = &(head)->sqh_first;                         \
 168     }                                                                  \
 169 } while (/*CONSTCOND*/0)
 170
 171 #define QSIMPLEQ_REMOVE_RCU(head, elm, type, field) do {            \
 172     if ((head)->sqh_first == (elm)) {                               \
 173         QSIMPLEQ_REMOVE_HEAD_RCU((head), field);                    \
 174     } else {                                                        \
 175         struct type *curr = (head)->sqh_first;                      \
 176         while (curr->field.sqe_next != (elm)) {                     \
 177             curr = curr->field.sqe_next;                            \
 178         }                                                           \
 179         qatomic_set(&curr->field.sqe_next,                          \
 180                    curr->field.sqe_next->field.sqe_next);           \
 181         if (curr->field.sqe_next == NULL) {                         \
 182             (head)->sqh_last = &(curr)->field.sqe_next;             \
 183         }                                                           \
 184     }                                                               \
 185 } while (/*CONSTCOND*/0)
 186
 187 #define QSIMPLEQ_FOREACH_RCU(var, head, field)                          \
 188     for ((var) = qatomic_rcu_read(&(head)->sqh_first);                  \
 189          (var);                                                         \
 190          (var) = qatomic_rcu_read(&(var)->field.sqe_next))
 191
 192 #define QSIMPLEQ_FOREACH_SAFE_RCU(var, head, field, next)                \
 193     for ((var) = qatomic_rcu_read(&(head)->sqh_first);                   \
 194          (var) && ((next) = qatomic_rcu_read(&(var)->field.sqe_next), 1);\
 195          (var) = (next))
 196
 197 /*
 198  * RCU tail queue
 199  */
 200
 201 /* Tail queue access methods */
 202 #define QTAILQ_EMPTY_RCU(head)      (qatomic_read(&(head)->tqh_first) == NULL)
 203 #define QTAILQ_FIRST_RCU(head)       qatomic_rcu_read(&(head)->tqh_first)
 204 #define QTAILQ_NEXT_RCU(elm, field)  qatomic_rcu_read(&(elm)->field.tqe_next)
 205
 206 /* Tail queue functions */
 207 #define QTAILQ_INSERT_HEAD_RCU(head, elm, field) do {                   \
 208     (elm)->field.tqe_next = (head)->tqh_first;                          \
 209     if ((elm)->field.tqe_next != NULL) {                                \
 210         (head)->tqh_first->field.tqe_circ.tql_prev =                    \
 211             &(elm)->field.tqe_circ;                                     \
 212     } else {                                                            \
 213         (head)->tqh_circ.tql_prev = &(elm)->field.tqe_circ;             \
 214     }                                                                   \
 215     qatomic_rcu_set(&(head)->tqh_first, (elm));                         \
 216     (elm)->field.tqe_circ.tql_prev = &(head)->tqh_circ;                 \
 217 } while (/*CONSTCOND*/0)
 218
 219 #define QTAILQ_INSERT_TAIL_RCU(head, elm, field) do {                   \
 220     (elm)->field.tqe_next = NULL;                                       \
 221     (elm)->field.tqe_circ.tql_prev = (head)->tqh_circ.tql_prev;         \
 222     qatomic_rcu_set(&(head)->tqh_circ.tql_prev->tql_next, (elm));       \
 223     (head)->tqh_circ.tql_prev = &(elm)->field.tqe_circ;                 \
 224 } while (/*CONSTCOND*/0)
 225
 226 #define QTAILQ_INSERT_AFTER_RCU(head, listelm, elm, field) do {         \
 227     (elm)->field.tqe_next = (listelm)->field.tqe_next;                  \
 228     if ((elm)->field.tqe_next != NULL) {                                \
 229         (elm)->field.tqe_next->field.tqe_circ.tql_prev =                \
 230             &(elm)->field.tqe_circ;                                     \
 231     } else {                                                            \
 232         (head)->tqh_circ.tql_prev = &(elm)->field.tqe_circ;             \
 233     }                                                                   \
 234     qatomic_rcu_set(&(listelm)->field.tqe_next, (elm));                 \
 235     (elm)->field.tqe_circ.tql_prev = &(listelm)->field.tqe_circ;        \
 236 } while (/*CONSTCOND*/0)
 237
 238 #define QTAILQ_INSERT_BEFORE_RCU(listelm, elm, field) do {                \
 239     (elm)->field.tqe_circ.tql_prev = (listelm)->field.tqe_circ.tql_prev;  \
 240     (elm)->field.tqe_next = (listelm);                                    \
 241     qatomic_rcu_set(&(listelm)->field.tqe_circ.tql_prev->tql_next, (elm));\
 242     (listelm)->field.tqe_circ.tql_prev = &(elm)->field.tqe_circ;          \
 243 } while (/*CONSTCOND*/0)
 244
 245 #define QTAILQ_REMOVE_RCU(head, elm, field) do {                        \
 246     if (((elm)->field.tqe_next) != NULL) {                              \
 247         (elm)->field.tqe_next->field.tqe_circ.tql_prev =                \
 248             (elm)->field.tqe_circ.tql_prev;                             \
 249     } else {                                                            \
 250         (head)->tqh_circ.tql_prev = (elm)->field.tqe_circ.tql_prev;     \
 251     }                                                                   \
 252     qatomic_set(&(elm)->field.tqe_circ.tql_prev->tql_next,              \
 253                 (elm)->field.tqe_next);                                 \
 254     (elm)->field.tqe_circ.tql_prev = NULL;                              \
 255 } while (/*CONSTCOND*/0)
 256
 257 #define QTAILQ_FOREACH_RCU(var, head, field)                            \
 258     for ((var) = qatomic_rcu_read(&(head)->tqh_first);                  \
 259          (var);                                                         \
 260          (var) = qatomic_rcu_read(&(var)->field.tqe_next))
 261
 262 #define QTAILQ_FOREACH_SAFE_RCU(var, head, field, next)                  \
 263     for ((var) = qatomic_rcu_read(&(head)->tqh_first);                   \
 264          (var) && ((next) = qatomic_rcu_read(&(var)->field.tqe_next), 1);\
 265          (var) = (next))
 266
 267 /*
 268  * RCU singly-linked list
 269  */
 270
 271 /* Singly-linked list access methods */
 272 #define QSLIST_EMPTY_RCU(head)      (qatomic_read(&(head)->slh_first) == NULL)
 273 #define QSLIST_FIRST_RCU(head)       qatomic_rcu_read(&(head)->slh_first)
 274 #define QSLIST_NEXT_RCU(elm, field)  qatomic_rcu_read(&(elm)->field.sle_next)
 275
 276 /* Singly-linked list functions */
 277 #define QSLIST_INSERT_HEAD_RCU(head, elm, field) do {           \
 278     (elm)->field.sle_next = (head)->slh_first;                  \
 279     qatomic_rcu_set(&(head)->slh_first, (elm));                 \
 280 } while (/*CONSTCOND*/0)
 281
 282 #define QSLIST_INSERT_AFTER_RCU(head, listelm, elm, field) do {         \
 283     (elm)->field.sle_next = (listelm)->field.sle_next;                  \
 284     qatomic_rcu_set(&(listelm)->field.sle_next, (elm));                 \
 285 } while (/*CONSTCOND*/0)
 286
 287 #define QSLIST_REMOVE_HEAD_RCU(head, field) do {                       \
 288     qatomic_set(&(head)->slh_first, (head)->slh_first->field.sle_next);\
 289 } while (/*CONSTCOND*/0)
 290
 291 #define QSLIST_REMOVE_RCU(head, elm, type, field) do {              \
 292     if ((head)->slh_first == (elm)) {                               \
 293         QSLIST_REMOVE_HEAD_RCU((head), field);                      \
 294     } else {                                                        \
 295         struct type *curr = (head)->slh_first;                      \
 296         while (curr->field.sle_next != (elm)) {                     \
 297             curr = curr->field.sle_next;                            \
 298         }                                                           \
 299         qatomic_set(&curr->field.sle_next,                          \
 300                    curr->field.sle_next->field.sle_next);           \
 301     }                                                               \
 302 } while (/*CONSTCOND*/0)
 303
 304 #define QSLIST_FOREACH_RCU(var, head, field)                          \
 305     for ((var) = qatomic_rcu_read(&(head)->slh_first);                \
 306          (var);                                                       \
 307          (var) = qatomic_rcu_read(&(var)->field.sle_next))
 308
 309 #define QSLIST_FOREACH_SAFE_RCU(var, head, field, next)                   \
 310     for ((var) = qatomic_rcu_read(&(head)->slh_first);                    \
 311          (var) && ((next) = qatomic_rcu_read(&(var)->field.sle_next), 1); \
 312          (var) = (next))
 313
 314 #ifdef __cplusplus
 315 }
 316 #endif
 317 #endif /* QEMU_RCU_QUEUE_H */