--- /dev/null
+#ifndef _URCU_WFCQUEUE_STATIC_H
+#define _URCU_WFCQUEUE_STATIC_H
+
+/*
+ * wfcqueue-static.h
+ *
+ * Userspace RCU library - Concurrent Queue with Wait-Free Enqueue/Blocking Dequeue
+ *
+ * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See wfcqueue.h for linking
+ * dynamically with the userspace rcu library.
+ *
+ * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright 2011-2012 - Lai Jiangshan <laijs@cn.fujitsu.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 <pthread.h>
+#include <assert.h>
+#include <poll.h>
+#include <stdbool.h>
+#include <urcu/compiler.h>
+#include <urcu/uatomic.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * Concurrent queue with wait-free enqueue/blocking dequeue.
+ *
+ * Inspired from half-wait-free/half-blocking queue implementation done by
+ * Paul E. McKenney.
+ *
+ * Mutual exclusion of __cds_wfcq_* API
+ *
+ * Unless otherwise stated, the caller must ensure mutual exclusion of
+ * queue update operations "dequeue" and "splice" (for source queue).
+ * Queue read operations "first" and "next" need to be protected against
+ * concurrent "dequeue" and "splice" (for source queue) by the caller.
+ * "enqueue", "splice" (for destination queue), and "empty" are the only
+ * operations that can be used without any mutual exclusion.
+ * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock().
+ *
+ * For convenience, cds_wfcq_dequeue_blocking() and
+ * cds_wfcq_splice_blocking() hold the dequeue lock.
+ */
+
+#define WFCQ_ADAPT_ATTEMPTS 10 /* Retry if being set */
+#define WFCQ_WAIT 10 /* Wait 10 ms if being set */
+
+/*
+ * cds_wfcq_node_init: initialize wait-free queue node.
+ */
+static inline void _cds_wfcq_node_init(struct cds_wfcq_node *node)
+{
+ node->next = NULL;
+}
+
+/*
+ * cds_wfcq_init: initialize wait-free queue.
+ */
+static inline void _cds_wfcq_init(struct cds_wfcq_head *head,
+ struct cds_wfcq_tail *tail)
+{
+ int ret;
+
+ /* Set queue head and tail */
+ _cds_wfcq_node_init(&head->node);
+ tail->p = &head->node;
+ ret = pthread_mutex_init(&head->lock, NULL);
+ assert(!ret);
+}
+
+/*
+ * cds_wfcq_empty: return whether wait-free queue is empty.
+ *
+ * No memory barrier is issued. No mutual exclusion is required.
+ */
+static inline bool _cds_wfcq_empty(struct cds_wfcq_head *head,
+ struct cds_wfcq_tail *tail)
+{
+ /*
+ * Queue is empty if no node is pointed by head->node.next nor
+ * tail->p. Even though the tail->p check is sufficient to find
+ * out of the queue is empty, we first check head->node.next as a
+ * common case to ensure that dequeuers do not frequently access
+ * enqueuer's tail->p cache line.
+ */
+ return CMM_LOAD_SHARED(head->node.next) == NULL
+ && CMM_LOAD_SHARED(tail->p) == &head->node;
+}
+
+static inline void _cds_wfcq_dequeue_lock(struct cds_wfcq_head *head,
+ struct cds_wfcq_tail *tail)
+{
+ int ret;
+
+ ret = pthread_mutex_lock(&head->lock);
+ assert(!ret);
+}
+
+static inline void _cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head,
+ struct cds_wfcq_tail *tail)
+{
+ int ret;
+
+ ret = pthread_mutex_unlock(&head->lock);
+ assert(!ret);
+}
+
+static inline void ___cds_wfcq_append(struct cds_wfcq_head *head,
+ struct cds_wfcq_tail *tail,
+ struct cds_wfcq_node *new_head,
+ struct cds_wfcq_node *new_tail)
+{
+ struct cds_wfcq_node *old_tail;
+
+ /*
+ * Implicit memory barrier before uatomic_xchg() orders earlier
+ * stores to data structure containing node and setting
+ * node->next to NULL before publication.
+ */
+ old_tail = uatomic_xchg(&tail->p, new_tail);
+
+ /*
+ * Implicit memory barrier after uatomic_xchg() orders store to
+ * q->tail before store to old_tail->next.
+ *
+ * At this point, dequeuers see a NULL tail->p->next, which
+ * indicates that the queue is being appended to. The following
+ * store will append "node" to the queue from a dequeuer
+ * perspective.
+ */
+ CMM_STORE_SHARED(old_tail->next, new_head);
+}
+
+/*
+ * cds_wfcq_enqueue: enqueue a node into a wait-free queue.
+ *
+ * Issues a full memory barrier before enqueue. No mutual exclusion is
+ * required.
+ */
+static inline void _cds_wfcq_enqueue(struct cds_wfcq_head *head,
+ struct cds_wfcq_tail *tail,
+ struct cds_wfcq_node *new_tail)
+{
+ ___cds_wfcq_append(head, tail, new_tail, new_tail);
+}
+
+/*
+ * Waiting for enqueuer to complete enqueue and return the next node.
+ */
+static inline struct cds_wfcq_node *
+___cds_wfcq_node_sync_next(struct cds_wfcq_node *node)
+{
+ struct cds_wfcq_node *next;
+ int attempt = 0;
+
+ /*
+ * Adaptative busy-looping waiting for enqueuer to complete enqueue.
+ */
+ while ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
+ if (++attempt >= WFCQ_ADAPT_ATTEMPTS) {
+ poll(NULL, 0, WFCQ_WAIT); /* Wait for 10ms */
+ attempt = 0;
+ } else {
+ caa_cpu_relax();
+ }
+ }
+
+ return next;
+}
+
+/*
+ * __cds_wfcq_first_blocking: get first node of a queue, without dequeuing.
+ *
+ * Content written into the node before enqueue is guaranteed to be
+ * consistent, but no other memory ordering is ensured.
+ * Should be called with cds_wfcq_dequeue_lock() held.
+ */
+static inline struct cds_wfcq_node *
+___cds_wfcq_first_blocking(struct cds_wfcq_head *head,
+ struct cds_wfcq_tail *tail)
+{
+ struct cds_wfcq_node *node;
+
+ if (_cds_wfcq_empty(head, tail))
+ return NULL;
+ node = ___cds_wfcq_node_sync_next(&head->node);
+ /* Load head->node.next before loading node's content */
+ cmm_smp_read_barrier_depends();
+ return node;
+}
+
+/*
+ * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
+ *
+ * Content written into the node before enqueue is guaranteed to be
+ * consistent, but no other memory ordering is ensured.
+ * Should be called with cds_wfcq_dequeue_lock() held.
+ */
+static inline struct cds_wfcq_node *
+___cds_wfcq_next_blocking(struct cds_wfcq_head *head,
+ struct cds_wfcq_tail *tail,
+ struct cds_wfcq_node *node)
+{
+ struct cds_wfcq_node *next;
+
+ /*
+ * Even though the following tail->p check is sufficient to find
+ * out if we reached the end of the queue, we first check
+ * node->next as a common case to ensure that iteration on nodes
+ * do not frequently access enqueuer's tail->p cache line.
+ */
+ if ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
+ /* Load node->next before tail->p */
+ cmm_smp_rmb();
+ if (CMM_LOAD_SHARED(tail->p) == node)
+ return NULL;
+ next = ___cds_wfcq_node_sync_next(node);
+ }
+ /* Load node->next before loading next's content */
+ cmm_smp_read_barrier_depends();
+ return next;
+}
+
+/*
+ * __cds_wfcq_dequeue_blocking: dequeue a node from the queue.
+ *
+ * No need to go on a waitqueue here, as there is no possible state in which the
+ * list could cause dequeue to busy-loop needlessly while waiting for another
+ * thread to be scheduled. The queue appears empty until tail->next is set by
+ * enqueue.
+ *
+ * Content written into the node before enqueue is guaranteed to be
+ * consistent, but no other memory ordering is ensured.
+ * It is valid to reuse and free a dequeued node immediately.
+ * Should be called with cds_wfcq_dequeue_lock() held.
+ */
+static inline struct cds_wfcq_node *
+___cds_wfcq_dequeue_blocking(struct cds_wfcq_head *head,
+ struct cds_wfcq_tail *tail)
+{
+ struct cds_wfcq_node *node, *next;
+
+ if (_cds_wfcq_empty(head, tail))
+ return NULL;
+
+ node = ___cds_wfcq_node_sync_next(&head->node);
+
+ if ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
+ /*
+ * @node is probably the only node in the queue.
+ * Try to move the tail to &q->head.
+ * q->head.next is set to NULL here, and stays
+ * NULL if the cmpxchg succeeds. Should the
+ * cmpxchg fail due to a concurrent enqueue, the
+ * q->head.next will be set to the next node.
+ * The implicit memory barrier before
+ * uatomic_cmpxchg() orders load node->next
+ * before loading q->tail.
+ * The implicit memory barrier before uatomic_cmpxchg
+ * orders load q->head.next before loading node's
+ * content.
+ */
+ _cds_wfcq_node_init(&head->node);
+ if (uatomic_cmpxchg(&tail->p, node, &head->node) == node)
+ return node;
+ next = ___cds_wfcq_node_sync_next(node);
+ }
+
+ /*
+ * Move queue head forward.
+ */
+ head->node.next = next;
+
+ /* Load q->head.next before loading node's content */
+ cmm_smp_read_barrier_depends();
+ return node;
+}
+
+/*
+ * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
+ *
+ * Dequeue all nodes from src_q.
+ * dest_q must be already initialized.
+ * Should be called with cds_wfcq_dequeue_lock() held on src_q.
+ */
+static inline void
+___cds_wfcq_splice_blocking(
+ struct cds_wfcq_head *dest_q_head,
+ struct cds_wfcq_tail *dest_q_tail,
+ struct cds_wfcq_head *src_q_head,
+ struct cds_wfcq_tail *src_q_tail)
+{
+ struct cds_wfcq_node *head, *tail;
+
+ if (_cds_wfcq_empty(src_q_head, src_q_tail))
+ return;
+
+ head = ___cds_wfcq_node_sync_next(&src_q_head->node);
+ _cds_wfcq_node_init(&src_q_head->node);
+
+ /*
+ * Memory barrier implied before uatomic_xchg() orders store to
+ * src_q->head before store to src_q->tail. This is required by
+ * concurrent enqueue on src_q, which exchanges the tail before
+ * updating the previous tail's next pointer.
+ */
+ tail = uatomic_xchg(&src_q_tail->p, &src_q_head->node);
+
+ /*
+ * Append the spliced content of src_q into dest_q. Does not
+ * require mutual exclusion on dest_q (wait-free).
+ */
+ ___cds_wfcq_append(dest_q_head, dest_q_tail, head, tail);
+}
+
+/*
+ * cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
+ *
+ * Content written into the node before enqueue is guaranteed to be
+ * consistent, but no other memory ordering is ensured.
+ * Mutual exlusion with (and only with) cds_wfcq_splice_blocking is
+ * ensured.
+ * It is valid to reuse and free a dequeued node immediately.
+ */
+static inline struct cds_wfcq_node *
+_cds_wfcq_dequeue_blocking(struct cds_wfcq_head *head,
+ struct cds_wfcq_tail *tail)
+{
+ struct cds_wfcq_node *retval;
+
+ _cds_wfcq_dequeue_lock(head, tail);
+ retval = ___cds_wfcq_dequeue_blocking(head, tail);
+ _cds_wfcq_dequeue_unlock(head, tail);
+ return retval;
+}
+
+/*
+ * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
+ *
+ * Dequeue all nodes from src_q.
+ * dest_q must be already initialized.
+ * Content written into the node before enqueue is guaranteed to be
+ * consistent, but no other memory ordering is ensured.
+ * Mutual exlusion with (and only with) cds_wfcq_dequeue_blocking is
+ * ensured.
+ */
+static inline void
+_cds_wfcq_splice_blocking(
+ struct cds_wfcq_head *dest_q_head,
+ struct cds_wfcq_tail *dest_q_tail,
+ struct cds_wfcq_head *src_q_head,
+ struct cds_wfcq_tail *src_q_tail)
+{
+ _cds_wfcq_dequeue_lock(src_q_head, src_q_tail);
+ ___cds_wfcq_splice_blocking(dest_q_head, dest_q_tail,
+ src_q_head, src_q_tail);
+ _cds_wfcq_dequeue_unlock(src_q_head, src_q_tail);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _URCU_WFCQUEUE_STATIC_H */
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