-#ifndef _URCU_WFSTACK_STATIC_H
-#define _URCU_WFSTACK_STATIC_H
+#ifndef _URCU_STATIC_WFSTACK_H
+#define _URCU_STATIC_WFSTACK_H
/*
- * wfstack-static.h
+ * urcu/static/wfstack.h
*
- * Userspace RCU library - Stack with Wait-Free push, Blocking pop.
+ * Userspace RCU library - Stack with with wait-free push, blocking traversal.
*
- * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See wfstack.h for linking
- * dynamically with the userspace rcu library.
+ * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu/wfstack.h for
+ * linking dynamically with the userspace rcu library.
*
- * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright 2010-2012 - 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
#include <pthread.h>
#include <assert.h>
#include <poll.h>
+#include <stdbool.h>
#include <urcu/compiler.h>
-#include <urcu/uatomic_arch.h>
+#include <urcu/uatomic.h>
#ifdef __cplusplus
extern "C" {
#endif
-#define CDS_WF_STACK_END ((void *)0x1UL)
+#define CDS_WFS_END ((void *) 0x1UL)
#define CDS_WFS_ADAPT_ATTEMPTS 10 /* Retry if being set */
#define CDS_WFS_WAIT 10 /* Wait 10 ms if being set */
+/*
+ * Stack with wait-free push, blocking traversal.
+ *
+ * Stack implementing push, pop, pop_all operations, as well as iterator
+ * on the stack head returned by pop_all.
+ *
+ * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all, cds_wfs_empty,
+ * cds_wfs_first.
+ * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, cds_wfs_next,
+ * iteration on 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_wfs_push __cds_wfs_pop __cds_wfs_pop_all
+ * cds_wfs_push - - -
+ * __cds_wfs_pop - X X
+ * __cds_wfs_pop_all - X -
+ *
+ * cds_wfs_pop and cds_wfs_pop_all use an internal mutex to provide
+ * synchronization.
+ */
+
+/*
+ * cds_wfs_node_init: initialize wait-free stack node.
+ */
+static inline
void _cds_wfs_node_init(struct cds_wfs_node *node)
{
node->next = NULL;
}
+/*
+ * __cds_wfs_init: initialize wait-free stack. Don't pair with
+ * any destroy function.
+ */
+static inline void ___cds_wfs_init(struct __cds_wfs_stack *s)
+{
+ s->head = CDS_WFS_END;
+}
+
+/*
+ * cds_wfs_init: initialize wait-free stack. Pair with
+ * cds_wfs_destroy().
+ */
+static inline
void _cds_wfs_init(struct cds_wfs_stack *s)
{
int ret;
- s->head = CDS_WF_STACK_END;
+ s->head = CDS_WFS_END;
ret = pthread_mutex_init(&s->lock, NULL);
assert(!ret);
}
-void _cds_wfs_push(struct cds_wfs_stack *s, struct cds_wfs_node *node)
+/*
+ * cds_wfs_destroy: destroy wait-free stack. Pair with
+ * cds_wfs_init().
+ */
+static inline
+void _cds_wfs_destroy(struct cds_wfs_stack *s)
+{
+ int ret = pthread_mutex_destroy(&s->lock);
+ assert(!ret);
+}
+
+static inline bool ___cds_wfs_end(void *node)
+{
+ return node == CDS_WFS_END;
+}
+
+/*
+ * cds_wfs_empty: return whether wait-free stack is empty.
+ *
+ * No memory barrier is issued. No mutual exclusion is required.
+ */
+static inline bool _cds_wfs_empty(cds_wfs_stack_ptr_t u_stack)
+{
+ struct __cds_wfs_stack *s = u_stack._s;
+
+ return ___cds_wfs_end(CMM_LOAD_SHARED(s->head));
+}
+
+/*
+ * cds_wfs_push: push a node into the stack.
+ *
+ * Issues a full memory barrier before push. No mutual exclusion is
+ * required.
+ *
+ * Returns 0 if the stack was empty prior to adding the node.
+ * Returns non-zero otherwise.
+ */
+static inline
+int _cds_wfs_push(cds_wfs_stack_ptr_t u_stack, struct cds_wfs_node *node)
{
- struct cds_wfs_node *old_head;
+ struct __cds_wfs_stack *s = u_stack._s;
+ struct cds_wfs_head *old_head, *new_head;
assert(node->next == NULL);
+ new_head = caa_container_of(node, struct cds_wfs_head, node);
/*
- * uatomic_xchg() implicit memory barrier orders earlier stores to node
- * (setting it to NULL) before publication.
+ * uatomic_xchg() implicit memory barrier orders earlier stores
+ * to node (setting it to NULL) before publication.
*/
- old_head = uatomic_xchg(&s->head, node);
+ old_head = uatomic_xchg(&s->head, new_head);
/*
- * At this point, dequeuers see a NULL node->next, they should busy-wait
- * until node->next is set to old_head.
+ * At this point, dequeuers see a NULL node->next, they should
+ * busy-wait until node->next is set to old_head.
*/
- CMM_STORE_SHARED(node->next, old_head);
+ CMM_STORE_SHARED(node->next, &old_head->node);
+ return !___cds_wfs_end(old_head);
}
/*
- * Returns NULL if stack is empty.
+ * Waiting for push to complete enqueue and return the next node.
*/
-struct cds_wfs_node *
-___cds_wfs_pop_blocking(struct cds_wfs_stack *s)
+static inline struct cds_wfs_node *
+___cds_wfs_node_sync_next(struct cds_wfs_node *node, int blocking)
{
- struct cds_wfs_node *head, *next;
+ struct cds_wfs_node *next;
int attempt = 0;
-retry:
- head = CMM_LOAD_SHARED(s->head);
- if (head == CDS_WF_STACK_END)
- return NULL;
/*
* Adaptative busy-looping waiting for push to complete.
*/
- while ((next = CMM_LOAD_SHARED(head->next)) == NULL) {
+ while ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
+ if (!blocking)
+ return CDS_WFS_WOULDBLOCK;
if (++attempt >= CDS_WFS_ADAPT_ATTEMPTS) {
- poll(NULL, 0, CDS_WFS_WAIT); /* Wait for 10ms */
+ (void) poll(NULL, 0, CDS_WFS_WAIT); /* Wait for 10ms */
attempt = 0;
- } else
+ } else {
caa_cpu_relax();
+ }
}
- if (uatomic_cmpxchg(&s->head, head, next) == head)
- return head;
- else
- goto retry; /* Concurrent modification. Retry. */
+
+ return next;
}
+static inline
struct cds_wfs_node *
-_cds_wfs_pop_blocking(struct cds_wfs_stack *s)
+___cds_wfs_pop(cds_wfs_stack_ptr_t u_stack, int *state, int blocking)
+{
+ struct cds_wfs_head *head, *new_head;
+ struct cds_wfs_node *next;
+ struct __cds_wfs_stack *s = u_stack._s;
+
+ if (state)
+ *state = 0;
+ for (;;) {
+ head = CMM_LOAD_SHARED(s->head);
+ if (___cds_wfs_end(head)) {
+ return NULL;
+ }
+ next = ___cds_wfs_node_sync_next(&head->node, blocking);
+ if (!blocking && next == CDS_WFS_WOULDBLOCK) {
+ return CDS_WFS_WOULDBLOCK;
+ }
+ new_head = caa_container_of(next, struct cds_wfs_head, node);
+ if (uatomic_cmpxchg(&s->head, head, new_head) == head) {
+ if (state && ___cds_wfs_end(new_head))
+ *state |= CDS_WFS_STATE_LAST;
+ return &head->node;
+ }
+ if (!blocking) {
+ return CDS_WFS_WOULDBLOCK;
+ }
+ /* busy-loop if head changed under us */
+ }
+}
+
+/*
+ * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
+ *
+ * Returns NULL if stack is empty.
+ *
+ * __cds_wfs_pop_blocking needs to be synchronized using one of the
+ * following techniques:
+ *
+ * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
+ * section. The caller must wait for a grace period to pass before
+ * freeing the returned node or modifying the cds_wfs_node structure.
+ * 2) Using mutual exclusion (e.g. mutexes) to protect
+ * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
+ * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
+ * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
+ *
+ * "state" saves state flags atomically sampled with pop operation.
+ */
+static inline
+struct cds_wfs_node *
+___cds_wfs_pop_with_state_blocking(cds_wfs_stack_ptr_t u_stack, int *state)
+{
+ return ___cds_wfs_pop(u_stack, state, 1);
+}
+
+static inline
+struct cds_wfs_node *
+___cds_wfs_pop_blocking(cds_wfs_stack_ptr_t u_stack)
+{
+ return ___cds_wfs_pop_with_state_blocking(u_stack, NULL);
+}
+
+/*
+ * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack.
+ *
+ * Same as __cds_wfs_pop_with_state_blocking, but returns
+ * CDS_WFS_WOULDBLOCK if it needs to block.
+ *
+ * "state" saves state flags atomically sampled with pop operation.
+ */
+static inline
+struct cds_wfs_node *
+___cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_ptr_t u_stack, int *state)
+{
+ return ___cds_wfs_pop(u_stack, state, 0);
+}
+
+/*
+ * __cds_wfs_pop_nonblocking: pop a node from the stack.
+ *
+ * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
+ * it needs to block.
+ */
+static inline
+struct cds_wfs_node *
+___cds_wfs_pop_nonblocking(cds_wfs_stack_ptr_t u_stack)
+{
+ return ___cds_wfs_pop_with_state_nonblocking(u_stack, NULL);
+}
+
+/*
+ * __cds_wfs_pop_all: pop all nodes from a stack.
+ *
+ * __cds_wfs_pop_all does not require any synchronization with other
+ * push, nor with other __cds_wfs_pop_all, but requires synchronization
+ * matching the technique used to synchronize __cds_wfs_pop_blocking:
+ *
+ * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
+ * section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
+ * must wait for a grace period to pass before freeing the returned
+ * node or modifying the cds_wfs_node structure. However, no RCU
+ * read-side critical section is needed around __cds_wfs_pop_all.
+ * 2) Using mutual exclusion (e.g. mutexes) to protect
+ * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
+ * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
+ * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
+ */
+static inline
+struct cds_wfs_head *
+___cds_wfs_pop_all(cds_wfs_stack_ptr_t u_stack)
+{
+ struct __cds_wfs_stack *s = u_stack._s;
+ struct cds_wfs_head *head;
+
+ /*
+ * Implicit memory barrier after uatomic_xchg() matches implicit
+ * memory barrier before uatomic_xchg() in cds_wfs_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().
+ */
+ head = uatomic_xchg(&s->head, CDS_WFS_END);
+ if (___cds_wfs_end(head))
+ return NULL;
+ return head;
+}
+
+/*
+ * cds_wfs_pop_lock: lock stack pop-protection mutex.
+ */
+static inline void _cds_wfs_pop_lock(struct cds_wfs_stack *s)
{
- struct cds_wfs_node *retnode;
int ret;
ret = pthread_mutex_lock(&s->lock);
assert(!ret);
- retnode = ___cds_wfs_pop_blocking(s);
+}
+
+/*
+ * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
+ */
+static inline void _cds_wfs_pop_unlock(struct cds_wfs_stack *s)
+{
+ int ret;
+
ret = pthread_mutex_unlock(&s->lock);
assert(!ret);
+}
+
+/*
+ * Call __cds_wfs_pop_with_state_blocking with an internal pop mutex held.
+ */
+static inline
+struct cds_wfs_node *
+_cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state)
+{
+ struct cds_wfs_node *retnode;
+
+ _cds_wfs_pop_lock(s);
+ retnode = ___cds_wfs_pop_with_state_blocking(s, state);
+ _cds_wfs_pop_unlock(s);
return retnode;
}
+/*
+ * Call _cds_wfs_pop_with_state_blocking without saving any state.
+ */
+static inline
+struct cds_wfs_node *
+_cds_wfs_pop_blocking(struct cds_wfs_stack *s)
+{
+ return _cds_wfs_pop_with_state_blocking(s, NULL);
+}
+
+/*
+ * Call __cds_wfs_pop_all with an internal pop mutex held.
+ */
+static inline
+struct cds_wfs_head *
+_cds_wfs_pop_all_blocking(struct cds_wfs_stack *s)
+{
+ struct cds_wfs_head *rethead;
+
+ _cds_wfs_pop_lock(s);
+ rethead = ___cds_wfs_pop_all(s);
+ _cds_wfs_pop_unlock(s);
+ return rethead;
+}
+
+/*
+ * cds_wfs_first: get first node of a popped stack.
+ *
+ * Content written into the node before enqueue is guaranteed to be
+ * consistent, but no other memory ordering is ensured.
+ *
+ * Used by for-like iteration macros in urcu/wfstack.h:
+ * cds_wfs_for_each_blocking()
+ * cds_wfs_for_each_blocking_safe()
+ *
+ * Returns NULL if popped stack is empty, top stack node otherwise.
+ */
+static inline struct cds_wfs_node *
+_cds_wfs_first(struct cds_wfs_head *head)
+{
+ if (___cds_wfs_end(head))
+ return NULL;
+ return &head->node;
+}
+
+static inline struct cds_wfs_node *
+___cds_wfs_next(struct cds_wfs_node *node, int blocking)
+{
+ struct cds_wfs_node *next;
+
+ next = ___cds_wfs_node_sync_next(node, blocking);
+ /*
+ * CDS_WFS_WOULDBLOCK != CSD_WFS_END, so we can check for end
+ * even if ___cds_wfs_node_sync_next returns CDS_WFS_WOULDBLOCK,
+ * and still return CDS_WFS_WOULDBLOCK.
+ */
+ if (___cds_wfs_end(next))
+ return NULL;
+ return next;
+}
+
+/*
+ * cds_wfs_next_blocking: get next node of a popped stack.
+ *
+ * Content written into the node before enqueue is guaranteed to be
+ * consistent, but no other memory ordering is ensured.
+ *
+ * Used by for-like iteration macros in urcu/wfstack.h:
+ * cds_wfs_for_each_blocking()
+ * cds_wfs_for_each_blocking_safe()
+ *
+ * Returns NULL if reached end of popped stack, non-NULL next stack
+ * node otherwise.
+ */
+static inline struct cds_wfs_node *
+_cds_wfs_next_blocking(struct cds_wfs_node *node)
+{
+ return ___cds_wfs_next(node, 1);
+}
+
+
+/*
+ * cds_wfs_next_nonblocking: get next node of a popped stack.
+ *
+ * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
+ * needs to block.
+ */
+static inline struct cds_wfs_node *
+_cds_wfs_next_nonblocking(struct cds_wfs_node *node)
+{
+ return ___cds_wfs_next(node, 0);
+}
+
#ifdef __cplusplus
}
#endif
-#endif /* _URCU_WFSTACK_STATIC_H */
+#endif /* _URCU_STATIC_WFSTACK_H */
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