#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 */
