--- /dev/null
+#ifndef _CDS_RCUDQ_H
+#define _CDS_RCUDQ_H
+
+/*
+ * Copyright (C) 2002 Free Software Foundation, Inc.
+ * (originally part of the GNU C Library)
+ * Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
+ *
+ * Copyright (C) 2009 Pierre-Marc Fournier
+ * Copyright (C) 2010-2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * 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
+ */
+
+#include <urcu/arch.h>
+#include <urcu/compiler.h>
+#include <urcu-pointer.h>
+#include <assert.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * RCU double-ended queue (DQ).
+ *
+ * Allow consistent forward and backward traversal of the DQ. For
+ * instance, given traversals occurring concurrently with a
+ * cds_rcudq_add() operation, if a node is seen by a forward RCU
+ * traversal, it will be seen by a following backward RCU traversal. The
+ * reverse is also true: if seen by backward RCU traversal, it will be
+ * seen by a following forward traversal.
+ *
+ * For node deletion, if forward and backward traversals execute
+ * concurrently with cds_rcudq_del(), if the node is not seen by a
+ * forward traversal, any following backward traversal is guaranteed not
+ * to see it. Likewise for backward traversal followed by forward
+ * traversal.
+ *
+ * Updates are RCU-aware. RCU-protected traversals end with _rcu
+ * suffix.
+ */
+
+#define CDS_RCUDQ_FLAG_SKIP (1U << 0) /* Traversal should skip node */
+
+/* Basic type for the DQ. */
+struct cds_rcudq_head {
+ struct cds_rcudq_head *next, *prev;
+ unsigned int flags;
+};
+
+#define CDS_RCUDQ_HEAD_INIT(name) \
+ { .prev = &(name), .next = &(name), .flags = 0 }
+
+/* Define a variable with the head and tail of the DQ. */
+#define CDS_RCUDQ_HEAD(name) \
+ struct cds_rcudq_head name = CDS_RCUDQ_HEAD_INIT(name)
+
+/* Initialize a new DQ head. */
+#define CDS_INIT_RCUDQ_HEAD(ptr) \
+ do { \
+ (ptr)->next = (ptr)->prev = (ptr); \
+ (ptr)->flags = 0; \
+ } while (0)
+
+/* Add new element at the head of the DQ. */
+static inline
+void cds_rcudq_add(struct cds_rcudq_head *newp, struct cds_rcudq_head *head)
+{
+ newp->next = head->next;
+ newp->prev = head;
+ newp->flags = CDS_RCUDQ_FLAG_SKIP;
+ cmm_smp_wmb(); /* Initialize newp before adding to dq */
+ _CMM_STORE_SHARED(head->next->prev, newp);
+ _CMM_STORE_SHARED(head->next, newp);
+ cmm_smp_wmb(); /* Order adding to dq before showing node */
+ CMM_STORE_SHARED(newp->flags, 0); /* Show node */
+}
+
+/* Add new element at the tail of the DQ. */
+static inline
+void cds_rcudq_add_tail(struct cds_rcudq_head *newp,
+ struct cds_rcudq_head *head)
+{
+ newp->next = head;
+ newp->prev = head->prev;
+ newp->flags = CDS_RCUDQ_FLAG_SKIP;
+ cmm_smp_wmb(); /* Initialize newp before adding to dq */
+ _CMM_STORE_SHARED(head->prev->next, newp);
+ _CMM_STORE_SHARED(head->prev, newp);
+ cmm_smp_wmb(); /* Order adding to dq before showing node */
+ CMM_STORE_SHARED(newp->flags, 0); /* Show node */
+}
+
+/* Remove element from list. */
+static inline
+void cds_rcudq_del(struct cds_rcudq_head *elem)
+{
+ _CMM_STORE_SHARED(elem->flags, CDS_RCUDQ_FLAG_SKIP); /* Hide node */
+ cmm_smp_wmb(); /* Order hiding node before removing from dq */
+ _CMM_STORE_SHARED(elem->next->prev, elem->prev);
+ CMM_STORE_SHARED(elem->prev->next, elem->next);
+}
+
+static inline
+int cds_rcudq_empty(struct cds_rcudq_head *head)
+{
+ return head == CMM_LOAD_SHARED(head->next);
+}
+
+/* Get typed element from list at a given position. */
+#define cds_rcudq_entry(ptr, type, member) \
+ caa_container_of(ptr, type, member)
+
+/*
+ * Traversals NOT RCU-protected. Need mutual exclusion against updates.
+ */
+
+/* Get first entry from a list. */
+#define cds_rcudq_first_entry(ptr, type, member) \
+ cds_rcudq_entry((ptr)->next, type, member)
+
+/* Iterate forward over the elements of the list. */
+#define cds_rcudq_for_each(pos, head) \
+ for (pos = (head)->next; pos != (head); pos = pos->next)
+
+/*
+ * Iterate forward over the elements list. The list elements can be
+ * removed from the list while doing this.
+ */
+#define cds_rcudq_for_each_safe(pos, p, head) \
+ for (pos = (head)->next, p = pos->next; \
+ pos != (head); \
+ pos = p, p = pos->next)
+
+#define cds_rcudq_for_each_entry(pos, head, member) \
+ for (pos = cds_rcudq_entry((head)->next, __typeof__(*pos), member); \
+ &pos->member != (head); \
+ pos = cds_rcudq_entry(pos->member.next, __typeof__(*pos), member))
+
+#define cds_rcudq_for_each_entry_safe(pos, p, head, member) \
+ for (pos = cds_rcudq_entry((head)->next, __typeof__(*pos), member), \
+ p = cds_rcudq_entry(pos->member.next, __typeof__(*pos), member); \
+ &pos->member != (head); \
+ pos = p, p = cds_rcudq_entry(pos->member.next, __typeof__(*pos), member))
+
+/* Iterate backward over the elements of the list. */
+#define cds_rcudq_for_each_reverse(pos, head) \
+ for (pos = (head)->prev; pos != (head); pos = pos->prev)
+
+/*
+ * Iterate backward over the elements list. The list elements can be
+ * removed from the list while doing this.
+ */
+#define cds_rcudq_for_each_reverse_safe(pos, p, head) \
+ for (pos = (head)->prev, p = pos->prev; \
+ pos != (head); \
+ pos = p, p = pos->prev)
+
+#define cds_rcudq_for_each_entry_reverse(pos, head, member) \
+ for (pos = cds_rcudq_entry((head)->prev, __typeof__(*pos), member); \
+ &pos->member != (head); \
+ pos = cds_rcudq_entry(pos->member.prev, __typeof__(*pos), member))
+
+#define cds_rcudq_for_each_entry_reverse_safe(pos, p, head, member) \
+ for (pos = cds_rcudq_entry((head)->prev, __typeof__(*pos), member), \
+ p = cds_rcudq_entry(pos->member.prev, __typeof__(*pos), member); \
+ &pos->member != (head); \
+ pos = p, p = cds_rcudq_entry(pos->member.prev, __typeof__(*pos), member))
+
+
+/*
+ * RCU-protected traversals.
+ *
+ * Iteration through all elements of the list must be done while rcu_read_lock()
+ * is held. cds_rcudq_get_next/cds_rcudq_get_prev are helpers to get the
+ * next and previous DQ nodes in RCU traversal.
+ */
+
+static inline struct cds_rcudq_head *cds_rcudq_get_next(struct cds_rcudq_head *pos,
+ struct cds_rcudq_head *head)
+{
+ unsigned int flags;
+
+ do {
+ pos = rcu_dereference(pos->next);
+ /* Implicit read barrier ordering load of next pointer before flags */
+ flags = CMM_LOAD_SHARED(pos->flags);
+ assert(!(flags & CDS_RCUDQ_FLAG_SKIP && pos == head));
+ } while (flags & CDS_RCUDQ_FLAG_SKIP);
+ return pos;
+}
+
+static inline struct cds_rcudq_head *cds_rcudq_get_prev(struct cds_rcudq_head *pos,
+ struct cds_rcudq_head *head)
+{
+ unsigned int flags;
+
+ do {
+ pos = rcu_dereference(pos->prev);
+ /* Implicit read barrier ordering load of prev pointer before flags */
+ flags = CMM_LOAD_SHARED(pos->flags);
+ assert(!(flags & CDS_RCUDQ_FLAG_SKIP && pos == head));
+ } while (flags & CDS_RCUDQ_FLAG_SKIP);
+ return pos;
+}
+
+/* Iterate forward over the elements of the list. RCU-protected. */
+#define cds_rcudq_for_each_rcu(pos, head) \
+ for (pos = cds_rcudq_get_next(head, head); pos != (head); \
+ pos = cds_rcudq_get_next(pos, head))
+
+/* Iterate forward through elements of the list. RCU-protected. */
+#define cds_rcudq_for_each_entry_rcu(pos, head, member) \
+ for (pos = cds_rcudq_entry(cds_rcudq_get_next(head, head), __typeof__(*pos), member); \
+ &pos->member != (head); \
+ pos = cds_rcudq_entry(cds_rcudq_get_next(&pos->member, head), __typeof__(*pos), member))
+
+/* Iterate backward over the elements of the list. RCU-protected. */
+#define cds_rcudq_for_each_reverse_rcu(pos, head) \
+ for (pos = cds_rcudq_get_prev(head, head); pos != (head); \
+ pos = cds_rcudq_get_prev(pos, head))
+
+/* Iterate forward through elements of the list. RCU-protected. */
+#define cds_rcudq_for_each_entry_reverse_rcu(pos, head, member) \
+ for (pos = cds_rcudq_entry(cds_rcudq_get_prev(head, head), __typeof__(*pos), member); \
+ &pos->member != (head); \
+ pos = cds_rcudq_entry(cds_rcudq_get_prev(&pos->member, head), __typeof__(*pos), member))
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _CDS_RCUDQ_H */
projects / userspace-rcu.git / commitdiff
