--- /dev/null
+#ifndef _URCU_STATIC_LFSTACK_H
+#define _URCU_STATIC_LFSTACK_H
+
+/*
+ * urcu/static/lfstack.h
+ *
+ * Userspace RCU library - Lock-Free Stack
+ *
+ * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu/lfstack.h for
+ * linking dynamically with the userspace rcu library.
+ *
+ * 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 <stdbool.h>
+#include <pthread.h>
+#include <assert.h>
+#include <urcu/uatomic.h>
+#include <urcu-pointer.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * Lock-free stack.
+ *
+ * Stack implementing push, pop, pop_all operations, as well as iterator
+ * on the stack head returned by pop_all.
+ *
+ * Synchronization table:
+ *
+ * External synchronization techniques described in the API below is
+ * required between pairs marked with "X". No external synchronization
+ * required between pairs marked with "-".
+ *
+ * cds_lfs_push __cds_lfs_pop __cds_lfs_pop_all
+ * cds_lfs_push - - -
+ * __cds_lfs_pop - X X
+ * __cds_lfs_pop_all - X -
+ *
+ * cds_lfs_pop_blocking and cds_lfs_pop_all_blocking use an internal
+ * mutex to provide synchronization.
+ */
+
+/*
+ * cds_lfs_node_init: initialize lock-free stack node.
+ */
+static inline
+void _cds_lfs_node_init(struct cds_lfs_node *node)
+{
+}
+
+/*
+ * cds_lfs_init: initialize lock-free stack (with lock). Pair with
+ * cds_lfs_destroy().
+ */
+static inline
+void _cds_lfs_init(struct cds_lfs_stack *s)
+{
+ int ret;
+
+ s->head = NULL;
+ ret = pthread_mutex_init(&s->lock, NULL);
+ assert(!ret);
+}
+
+/*
+ * cds_lfs_destroy: destroy lock-free stack (with lock). Pair with
+ * cds_lfs_init().
+ */
+static inline
+void _cds_lfs_destroy(struct cds_lfs_stack *s)
+{
+ int ret = pthread_mutex_destroy(&s->lock);
+ assert(!ret);
+}
+
+/*
+ * ___cds_lfs_init: initialize lock-free stack (without lock).
+ * Don't pair with any destroy function.
+ */
+static inline
+void ___cds_lfs_init(struct __cds_lfs_stack *s)
+{
+ s->head = NULL;
+}
+
+static inline
+bool ___cds_lfs_empty_head(struct cds_lfs_head *head)
+{
+ return head == NULL;
+}
+
+/*
+ * cds_lfs_empty: return whether lock-free stack is empty.
+ *
+ * No memory barrier is issued. No mutual exclusion is required.
+ */
+static inline
+bool _cds_lfs_empty(cds_lfs_stack_ptr_t s)
+{
+ return ___cds_lfs_empty_head(CMM_LOAD_SHARED(s._s->head));
+}
+
+/*
+ * cds_lfs_push: push a node into the stack.
+ *
+ * Does not require any synchronization with other push nor pop.
+ *
+ * Lock-free stack push is not subject to ABA problem, so no need to
+ * take the RCU read-side lock. Even if "head" changes between two
+ * uatomic_cmpxchg() invocations here (being popped, and then pushed
+ * again by one or more concurrent threads), the second
+ * uatomic_cmpxchg() invocation only cares about pushing a new entry at
+ * the head of the stack, ensuring consistency by making sure the new
+ * node->next is the same pointer value as the value replaced as head.
+ * It does not care about the content of the actual next node, so it can
+ * very well be reallocated between the two uatomic_cmpxchg().
+ *
+ * We take the approach of expecting the stack to be usually empty, so
+ * we first try an initial uatomic_cmpxchg() on a NULL old_head, and
+ * retry if the old head was non-NULL (the value read by the first
+ * uatomic_cmpxchg() is used as old head for the following loop). The
+ * upside of this scheme is to minimize the amount of cacheline traffic,
+ * always performing an exclusive cacheline access, rather than doing
+ * non-exclusive followed by exclusive cacheline access (which would be
+ * required if we first read the old head value). This design decision
+ * might be revisited after more thorough benchmarking on various
+ * platforms.
+ *
+ * Returns 0 if the stack was empty prior to adding the node.
+ * Returns non-zero otherwise.
+ */
+static inline
+bool _cds_lfs_push(cds_lfs_stack_ptr_t u_s,
+ struct cds_lfs_node *node)
+{
+ struct __cds_lfs_stack *s = u_s._s;
+ struct cds_lfs_head *head = NULL;
+ struct cds_lfs_head *new_head =
+ caa_container_of(node, struct cds_lfs_head, node);
+
+ for (;;) {
+ struct cds_lfs_head *old_head = head;
+
+ /*
+ * node->next is still private at this point, no need to
+ * perform a _CMM_STORE_SHARED().
+ */
+ node->next = &head->node;
+ /*
+ * uatomic_cmpxchg() implicit memory barrier orders earlier
+ * stores to node before publication.
+ */
+ head = uatomic_cmpxchg(&s->head, old_head, new_head);
+ if (old_head == head)
+ break;
+ }
+ return !___cds_lfs_empty_head(head);
+}
+
+/*
+ * __cds_lfs_pop: pop a node from the stack.
+ *
+ * Returns NULL if stack is empty.
+ *
+ * __cds_lfs_pop needs to be synchronized using one of the following
+ * techniques:
+ *
+ * 1) Calling __cds_lfs_pop under rcu read lock critical section.
+ * Both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a
+ * grace period to pass before freeing the returned node or pushing
+ * the node back into the stack. It is valid to overwrite the content
+ * of cds_lfs_node immediately after __cds_lfs_pop and
+ * __cds_lfs_pop_all. No RCU read-side critical section is needed
+ * around __cds_lfs_pop_all.
+ * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop
+ * and __cds_lfs_pop_all callers.
+ * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
+ * __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
+ */
+static inline
+struct cds_lfs_node *___cds_lfs_pop(cds_lfs_stack_ptr_t u_s)
+{
+ struct __cds_lfs_stack *s = u_s._s;
+
+ for (;;) {
+ struct cds_lfs_head *head, *next_head;
+ struct cds_lfs_node *next;
+
+ head = _CMM_LOAD_SHARED(s->head);
+ if (___cds_lfs_empty_head(head))
+ return NULL; /* Empty stack */
+
+ /*
+ * Read head before head->next. Matches the implicit
+ * memory barrier before uatomic_cmpxchg() in
+ * cds_lfs_push.
+ */
+ cmm_smp_read_barrier_depends();
+ next = _CMM_LOAD_SHARED(head->node.next);
+ next_head = caa_container_of(next,
+ struct cds_lfs_head, node);
+ if (uatomic_cmpxchg(&s->head, head, next_head) == head)
+ return &head->node;
+ /* busy-loop if head changed under us */
+ }
+}
+
+/*
+ * __cds_lfs_pop_all: pop all nodes from a stack.
+ *
+ * __cds_lfs_pop_all does not require any synchronization with other
+ * push, nor with other __cds_lfs_pop_all, but requires synchronization
+ * matching the technique used to synchronize __cds_lfs_pop:
+ *
+ * 1) If __cds_lfs_pop is called under rcu read lock critical section,
+ * both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a
+ * grace period to pass before freeing the returned node or pushing
+ * the node back into the stack. It is valid to overwrite the content
+ * of cds_lfs_node immediately after __cds_lfs_pop and
+ * __cds_lfs_pop_all. No RCU read-side critical section is needed
+ * around __cds_lfs_pop_all.
+ * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop and
+ * __cds_lfs_pop_all callers.
+ * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
+ * __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
+ */
+static inline
+struct cds_lfs_head *___cds_lfs_pop_all(cds_lfs_stack_ptr_t u_s)
+{
+ struct __cds_lfs_stack *s = u_s._s;
+
+ /*
+ * Implicit memory barrier after uatomic_xchg() matches implicit
+ * memory barrier before uatomic_cmpxchg() in cds_lfs_push. It
+ * ensures that all nodes of the returned list are consistent.
+ * There is no need to issue memory barriers when iterating on
+ * the returned list, because the full memory barrier issued
+ * prior to each uatomic_cmpxchg, which each write to head, are
+ * taking care to order writes to each node prior to the full
+ * memory barrier after this uatomic_xchg().
+ */
+ return uatomic_xchg(&s->head, NULL);
+}
+
+/*
+ * cds_lfs_pop_lock: lock stack pop-protection mutex.
+ */
+static inline void _cds_lfs_pop_lock(struct cds_lfs_stack *s)
+{
+ int ret;
+
+ ret = pthread_mutex_lock(&s->lock);
+ assert(!ret);
+}
+
+/*
+ * cds_lfs_pop_unlock: unlock stack pop-protection mutex.
+ */
+static inline void _cds_lfs_pop_unlock(struct cds_lfs_stack *s)
+{
+ int ret;
+
+ ret = pthread_mutex_unlock(&s->lock);
+ assert(!ret);
+}
+
+/*
+ * Call __cds_lfs_pop with an internal pop mutex held.
+ */
+static inline
+struct cds_lfs_node *
+_cds_lfs_pop_blocking(struct cds_lfs_stack *s)
+{
+ struct cds_lfs_node *retnode;
+
+ _cds_lfs_pop_lock(s);
+ retnode = ___cds_lfs_pop(s);
+ _cds_lfs_pop_unlock(s);
+ return retnode;
+}
+
+/*
+ * Call __cds_lfs_pop_all with an internal pop mutex held.
+ */
+static inline
+struct cds_lfs_head *
+_cds_lfs_pop_all_blocking(struct cds_lfs_stack *s)
+{
+ struct cds_lfs_head *rethead;
+
+ _cds_lfs_pop_lock(s);
+ rethead = ___cds_lfs_pop_all(s);
+ _cds_lfs_pop_unlock(s);
+ return rethead;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _URCU_STATIC_LFSTACK_H */
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