| #ifndef QEMU_RCU_QUEUE_H |
| #define QEMU_RCU_QUEUE_H |
| |
| /* |
| * rcu_queue.h |
| * |
| * RCU-friendly versions of the queue.h primitives. |
| * |
| * This library is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU Lesser General Public |
| * License as published by the Free Software Foundation; either |
| * version 2.1 of the License, or (at your option) any later version. |
| * |
| * This library is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * Lesser General Public License for more details. |
| * |
| * You should have received a copy of the GNU Lesser General Public |
| * License along with this library; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| * |
| * Copyright (c) 2013 Mike D. Day, IBM Corporation. |
| * |
| * IBM's contributions to this file may be relicensed under LGPLv2 or later. |
| */ |
| |
| #include "qemu/queue.h" |
| #include "qemu/atomic.h" |
| |
| #ifdef __cplusplus |
| extern "C" { |
| #endif |
| |
| |
| /* |
| * List access methods. |
| */ |
| #define QLIST_EMPTY_RCU(head) (atomic_rcu_read(&(head)->lh_first) == NULL) |
| #define QLIST_FIRST_RCU(head) (atomic_rcu_read(&(head)->lh_first)) |
| #define QLIST_NEXT_RCU(elm, field) (atomic_rcu_read(&(elm)->field.le_next)) |
| |
| /* |
| * List functions. |
| */ |
| |
| |
| /* |
| * The difference between atomic_read/set and atomic_rcu_read/set |
| * is in the including of a read/write memory barrier to the volatile |
| * access. atomic_rcu_* macros include the memory barrier, the |
| * plain atomic macros do not. Therefore, it should be correct to |
| * issue a series of reads or writes to the same element using only |
| * the atomic_* macro, until the last read or write, which should be |
| * atomic_rcu_* to introduce a read or write memory barrier as |
| * appropriate. |
| */ |
| |
| /* Upon publication of the listelm->next value, list readers |
| * will see the new node when following next pointers from |
| * antecedent nodes, but may not see the new node when following |
| * prev pointers from subsequent nodes until after the RCU grace |
| * period expires. |
| * see linux/include/rculist.h __list_add_rcu(new, prev, next) |
| */ |
| #define QLIST_INSERT_AFTER_RCU(listelm, elm, field) do { \ |
| (elm)->field.le_next = (listelm)->field.le_next; \ |
| (elm)->field.le_prev = &(listelm)->field.le_next; \ |
| atomic_rcu_set(&(listelm)->field.le_next, (elm)); \ |
| if ((elm)->field.le_next != NULL) { \ |
| (elm)->field.le_next->field.le_prev = \ |
| &(elm)->field.le_next; \ |
| } \ |
| } while (/*CONSTCOND*/0) |
| |
| /* Upon publication of the listelm->prev->next value, list |
| * readers will see the new element when following prev pointers |
| * from subsequent elements, but may not see the new element |
| * when following next pointers from antecedent elements |
| * until after the RCU grace period expires. |
| */ |
| #define QLIST_INSERT_BEFORE_RCU(listelm, elm, field) do { \ |
| (elm)->field.le_prev = (listelm)->field.le_prev; \ |
| (elm)->field.le_next = (listelm); \ |
| atomic_rcu_set((listelm)->field.le_prev, (elm)); \ |
| (listelm)->field.le_prev = &(elm)->field.le_next; \ |
| } while (/*CONSTCOND*/0) |
| |
| /* Upon publication of the head->first value, list readers |
| * will see the new element when following the head, but may |
| * not see the new element when following prev pointers from |
| * subsequent elements until after the RCU grace period has |
| * expired. |
| */ |
| #define QLIST_INSERT_HEAD_RCU(head, elm, field) do { \ |
| (elm)->field.le_prev = &(head)->lh_first; \ |
| (elm)->field.le_next = (head)->lh_first; \ |
| atomic_rcu_set((&(head)->lh_first), (elm)); \ |
| if ((elm)->field.le_next != NULL) { \ |
| (elm)->field.le_next->field.le_prev = \ |
| &(elm)->field.le_next; \ |
| } \ |
| } while (/*CONSTCOND*/0) |
| |
| |
| /* prior to publication of the elm->prev->next value, some list |
| * readers may still see the removed element when following |
| * the antecedent's next pointer. |
| */ |
| #define QLIST_REMOVE_RCU(elm, field) do { \ |
| if ((elm)->field.le_next != NULL) { \ |
| (elm)->field.le_next->field.le_prev = \ |
| (elm)->field.le_prev; \ |
| } \ |
| *(elm)->field.le_prev = (elm)->field.le_next; \ |
| } while (/*CONSTCOND*/0) |
| |
| /* List traversal must occur within an RCU critical section. */ |
| #define QLIST_FOREACH_RCU(var, head, field) \ |
| for ((var) = atomic_rcu_read(&(head)->lh_first); \ |
| (var); \ |
| (var) = atomic_rcu_read(&(var)->field.le_next)) |
| |
| /* List traversal must occur within an RCU critical section. */ |
| #define QLIST_FOREACH_SAFE_RCU(var, head, field, next_var) \ |
| for ((var) = (atomic_rcu_read(&(head)->lh_first)); \ |
| (var) && \ |
| ((next_var) = atomic_rcu_read(&(var)->field.le_next), 1); \ |
| (var) = (next_var)) |
| |
| #ifdef __cplusplus |
| } |
| #endif |
| #endif /* QEMU_RCU_QUEUE_H */ |