--- /dev/null
+#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 */
Code Review / kvmfornfv.git / blobdiff