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