LXR qemu/include/qemu/rcu

   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/*
  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 */
 310