X-Git-Url: http://git.liburcu.org/?p=userspace-rcu.git;a=blobdiff_plain;f=include%2Furcu%2Fwfcqueue.h;fp=include%2Furcu%2Fwfcqueue.h;h=6c6ebba9e4453257da70484cecc6840bbdab0364;hp=0000000000000000000000000000000000000000;hb=6893800a4d1cc14dff0395ddcd660a5138db183d;hpb=a59f39055b5ecb77b68cf78b9839aa9e8e4ec332 diff --git a/include/urcu/wfcqueue.h b/include/urcu/wfcqueue.h new file mode 100644 index 0000000..6c6ebba --- /dev/null +++ b/include/urcu/wfcqueue.h @@ -0,0 +1,488 @@ +#ifndef _URCU_WFCQUEUE_H +#define _URCU_WFCQUEUE_H + +/* + * urcu/wfcqueue.h + * + * Userspace RCU library - Concurrent Queue with Wait-Free Enqueue/Blocking Dequeue + * + * Copyright 2010-2012 - Mathieu Desnoyers + * Copyright 2011-2012 - Lai Jiangshan + * + * 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 +#include +#include +#include +#include + +#ifdef __cplusplus +extern "C" { +#endif + +/* + * Concurrent queue with wait-free enqueue/blocking dequeue. + * + * This queue has been designed and implemented collaboratively by + * Mathieu Desnoyers and Lai Jiangshan. Inspired from + * half-wait-free/half-blocking queue implementation done by Paul E. + * McKenney. + */ + +#define CDS_WFCQ_WOULDBLOCK ((struct cds_wfcq_node *) -1UL) + +enum cds_wfcq_ret { + CDS_WFCQ_RET_WOULDBLOCK = -1, + CDS_WFCQ_RET_DEST_EMPTY = 0, + CDS_WFCQ_RET_DEST_NON_EMPTY = 1, + CDS_WFCQ_RET_SRC_EMPTY = 2, +}; + +enum cds_wfcq_state { + CDS_WFCQ_STATE_LAST = (1U << 0), +}; + +struct cds_wfcq_node { + struct cds_wfcq_node *next; +}; + +/* + * Do not put head and tail on the same cache-line if concurrent + * enqueue/dequeue are expected from many CPUs. This eliminates + * false-sharing between enqueue and dequeue. + */ +struct __cds_wfcq_head { + struct cds_wfcq_node node; +}; + +struct cds_wfcq_head { + struct cds_wfcq_node node; + pthread_mutex_t lock; +}; + +#ifndef __cplusplus +/* + * The transparent union allows calling functions that work on both + * struct cds_wfcq_head and struct __cds_wfcq_head on any of those two + * types. + */ +typedef union { + struct __cds_wfcq_head *_h; + struct cds_wfcq_head *h; +} __attribute__((__transparent_union__)) cds_wfcq_head_ptr_t; + +/* + * This static inline is only present for compatibility with C++. It is + * effect-less in C. + */ +static inline struct __cds_wfcq_head *__cds_wfcq_head_cast(struct __cds_wfcq_head *head) +{ + return head; +} + +/* + * This static inline is only present for compatibility with C++. It is + * effect-less in C. + */ +static inline struct cds_wfcq_head *cds_wfcq_head_cast(struct cds_wfcq_head *head) +{ + return head; +} +#else /* #ifndef __cplusplus */ + +/* C++ ignores transparent union. */ +typedef union { + struct __cds_wfcq_head *_h; + struct cds_wfcq_head *h; +} cds_wfcq_head_ptr_t; + +/* C++ ignores transparent union. Requires an explicit conversion. */ +static inline cds_wfcq_head_ptr_t __cds_wfcq_head_cast(struct __cds_wfcq_head *head) +{ + cds_wfcq_head_ptr_t ret = { ._h = head }; + return ret; +} +/* C++ ignores transparent union. Requires an explicit conversion. */ +static inline cds_wfcq_head_ptr_t cds_wfcq_head_cast(struct cds_wfcq_head *head) +{ + cds_wfcq_head_ptr_t ret = { .h = head }; + return ret; +} +#endif /* #else #ifndef __cplusplus */ + +struct cds_wfcq_tail { + struct cds_wfcq_node *p; +}; + +#ifdef _LGPL_SOURCE + +#include + +#define cds_wfcq_node_init _cds_wfcq_node_init +#define cds_wfcq_init _cds_wfcq_init +#define __cds_wfcq_init ___cds_wfcq_init +#define cds_wfcq_destroy _cds_wfcq_destroy +#define cds_wfcq_empty _cds_wfcq_empty +#define cds_wfcq_enqueue _cds_wfcq_enqueue + +/* Dequeue locking */ +#define cds_wfcq_dequeue_lock _cds_wfcq_dequeue_lock +#define cds_wfcq_dequeue_unlock _cds_wfcq_dequeue_unlock + +/* Locking performed within cds_wfcq calls. */ +#define cds_wfcq_dequeue_blocking _cds_wfcq_dequeue_blocking +#define cds_wfcq_dequeue_with_state_blocking \ + _cds_wfcq_dequeue_with_state_blocking +#define cds_wfcq_splice_blocking _cds_wfcq_splice_blocking +#define cds_wfcq_first_blocking _cds_wfcq_first_blocking +#define cds_wfcq_next_blocking _cds_wfcq_next_blocking + +/* Locking ensured by caller by holding cds_wfcq_dequeue_lock() */ +#define __cds_wfcq_dequeue_blocking ___cds_wfcq_dequeue_blocking +#define __cds_wfcq_dequeue_with_state_blocking \ + ___cds_wfcq_dequeue_with_state_blocking +#define __cds_wfcq_splice_blocking ___cds_wfcq_splice_blocking +#define __cds_wfcq_first_blocking ___cds_wfcq_first_blocking +#define __cds_wfcq_next_blocking ___cds_wfcq_next_blocking + +/* + * Locking ensured by caller by holding cds_wfcq_dequeue_lock(). + * Non-blocking: deque, first, next return CDS_WFCQ_WOULDBLOCK if they + * need to block. splice returns nonzero if it needs to block. + */ +#define __cds_wfcq_dequeue_nonblocking ___cds_wfcq_dequeue_nonblocking +#define __cds_wfcq_dequeue_with_state_nonblocking \ + ___cds_wfcq_dequeue_with_state_nonblocking +#define __cds_wfcq_splice_nonblocking ___cds_wfcq_splice_nonblocking +#define __cds_wfcq_first_nonblocking ___cds_wfcq_first_nonblocking +#define __cds_wfcq_next_nonblocking ___cds_wfcq_next_nonblocking + +#else /* !_LGPL_SOURCE */ + +/* + * Mutual exclusion of cds_wfcq_* / __cds_wfcq_* API + * + * 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 "-". + * + * Legend: + * [1] cds_wfcq_enqueue + * [2] __cds_wfcq_splice (destination queue) + * [3] __cds_wfcq_dequeue + * [4] __cds_wfcq_splice (source queue) + * [5] __cds_wfcq_first + * [6] __cds_wfcq_next + * + * [1] [2] [3] [4] [5] [6] + * [1] - - - - - - + * [2] - - - - - - + * [3] - - X X X X + * [4] - - X - X X + * [5] - - X X - - + * [6] - - X X - - + * + * 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. + * + * Besides locking, mutual exclusion of dequeue, splice and iteration + * can be ensured by performing all of those operations from a single + * thread, without requiring any lock. + */ + +/* + * cds_wfcq_node_init: initialize wait-free queue node. + */ +extern void cds_wfcq_node_init(struct cds_wfcq_node *node); + +/* + * cds_wfcq_init: initialize wait-free queue. Pair with + * cds_wfcq_destroy(). + */ +extern void cds_wfcq_init(struct cds_wfcq_head *head, + struct cds_wfcq_tail *tail); + +/* + * cds_wfcq_destroy: destroy wait-free queue. Pair with + * cds_wfcq_init(). + */ +extern void cds_wfcq_destroy(struct cds_wfcq_head *head, + struct cds_wfcq_tail *tail); + +/* + * __cds_wfcq_init: initialize wait-free queue (without lock). Don't + * pair with any destroy function. + */ +extern void __cds_wfcq_init(struct __cds_wfcq_head *head, + struct cds_wfcq_tail *tail); + +/* + * cds_wfcq_empty: return whether wait-free queue is empty. + * + * No memory barrier is issued. No mutual exclusion is required. + */ +extern bool cds_wfcq_empty(cds_wfcq_head_ptr_t head, + struct cds_wfcq_tail *tail); + +/* + * cds_wfcq_dequeue_lock: take the dequeue mutual exclusion lock. + */ +extern void cds_wfcq_dequeue_lock(struct cds_wfcq_head *head, + struct cds_wfcq_tail *tail); + +/* + * cds_wfcq_dequeue_unlock: release the dequeue mutual exclusion lock. + */ +extern void cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head, + struct cds_wfcq_tail *tail); + +/* + * cds_wfcq_enqueue: enqueue a node into a wait-free queue. + * + * Issues a full memory barrier before enqueue. No mutual exclusion is + * required. + * + * Returns false if the queue was empty prior to adding the node. + * Returns true otherwise. + */ +extern bool cds_wfcq_enqueue(cds_wfcq_head_ptr_t head, + struct cds_wfcq_tail *tail, + struct cds_wfcq_node *node); + +/* + * 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. + * It is valid to reuse and free a dequeued node immediately. + * Mutual exclusion with cds_wfcq_dequeue_blocking and dequeue lock is + * ensured. + */ +extern struct cds_wfcq_node *cds_wfcq_dequeue_blocking( + struct cds_wfcq_head *head, + struct cds_wfcq_tail *tail); + +/* + * cds_wfcq_dequeue_with_state_blocking: dequeue with state. + * + * Same as cds_wfcq_dequeue_blocking, but saves whether dequeueing the + * last node of the queue into state (CDS_WFCQ_STATE_LAST). + */ +extern struct cds_wfcq_node *cds_wfcq_dequeue_with_state_blocking( + struct cds_wfcq_head *head, + struct cds_wfcq_tail *tail, + int *state); + +/* + * 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 exclusion with cds_wfcq_dequeue_blocking and dequeue lock is + * ensured. + * + * Returns enum cds_wfcq_ret which indicates the state of the src or + * dest queue. + */ +extern enum cds_wfcq_ret 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_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. + * It is valid to reuse and free a dequeued node immediately. + * Dequeue/splice/iteration mutual exclusion should be ensured by the + * caller. + */ +extern struct cds_wfcq_node *__cds_wfcq_dequeue_blocking( + cds_wfcq_head_ptr_t head, + struct cds_wfcq_tail *tail); + +/* + * __cds_wfcq_dequeue_with_state_blocking: dequeue with state. + * + * Same as __cds_wfcq_dequeue_blocking, but saves whether dequeueing the + * last node of the queue into state (CDS_WFCQ_STATE_LAST). + */ +extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_blocking( + cds_wfcq_head_ptr_t head, + struct cds_wfcq_tail *tail, + int *state); + +/* + * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue. + * + * Same as __cds_wfcq_dequeue_blocking, but returns CDS_WFCQ_WOULDBLOCK + * if it needs to block. + */ +extern struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking( + cds_wfcq_head_ptr_t head, + struct cds_wfcq_tail *tail); + +/* + * __cds_wfcq_dequeue_with_state_blocking: dequeue with state. + * + * Same as __cds_wfcq_dequeue_nonblocking, but saves whether dequeueing + * the last node of the queue into state (CDS_WFCQ_STATE_LAST). + */ +extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_nonblocking( + cds_wfcq_head_ptr_t head, + struct cds_wfcq_tail *tail, + int *state); + +/* + * __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. + * Mutual exclusion for src_q should be ensured by the caller as + * specified in the "Synchronisation table". + * Returns enum cds_wfcq_ret which indicates the state of the src or + * dest queue. Never returns CDS_WFCQ_RET_WOULDBLOCK. + */ +extern enum cds_wfcq_ret __cds_wfcq_splice_blocking( + cds_wfcq_head_ptr_t dest_q_head, + struct cds_wfcq_tail *dest_q_tail, + cds_wfcq_head_ptr_t src_q_head, + struct cds_wfcq_tail *src_q_tail); + +/* + * __cds_wfcq_splice_nonblocking: enqueue all src_q nodes at the end of dest_q. + * + * Same as __cds_wfcq_splice_blocking, but returns + * CDS_WFCQ_RET_WOULDBLOCK if it needs to block. + */ +extern enum cds_wfcq_ret __cds_wfcq_splice_nonblocking( + cds_wfcq_head_ptr_t dest_q_head, + struct cds_wfcq_tail *dest_q_tail, + cds_wfcq_head_ptr_t src_q_head, + struct cds_wfcq_tail *src_q_tail); + +/* + * __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. + * Dequeue/splice/iteration mutual exclusion should be ensured by the + * caller. + * + * Used by for-like iteration macros: + * __cds_wfcq_for_each_blocking() + * __cds_wfcq_for_each_blocking_safe() + * + * Returns NULL if queue is empty, first node otherwise. + */ +extern struct cds_wfcq_node *__cds_wfcq_first_blocking( + cds_wfcq_head_ptr_t head, + struct cds_wfcq_tail *tail); + +/* + * __cds_wfcq_first_nonblocking: get first node of a queue, without dequeuing. + * + * Same as __cds_wfcq_first_blocking, but returns CDS_WFCQ_WOULDBLOCK if + * it needs to block. + */ +extern struct cds_wfcq_node *__cds_wfcq_first_nonblocking( + cds_wfcq_head_ptr_t head, + struct cds_wfcq_tail *tail); + +/* + * __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. + * Dequeue/splice/iteration mutual exclusion should be ensured by the + * caller. + * + * Used by for-like iteration macros: + * __cds_wfcq_for_each_blocking() + * __cds_wfcq_for_each_blocking_safe() + * + * Returns NULL if reached end of queue, non-NULL next queue node + * otherwise. + */ +extern struct cds_wfcq_node *__cds_wfcq_next_blocking( + cds_wfcq_head_ptr_t head, + struct cds_wfcq_tail *tail, + struct cds_wfcq_node *node); + +/* + * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing. + * + * Same as __cds_wfcq_next_blocking, but returns CDS_WFCQ_WOULDBLOCK if + * it needs to block. + */ +extern struct cds_wfcq_node *__cds_wfcq_next_nonblocking( + cds_wfcq_head_ptr_t head, + struct cds_wfcq_tail *tail, + struct cds_wfcq_node *node); + +#endif /* !_LGPL_SOURCE */ + +/* + * __cds_wfcq_for_each_blocking: Iterate over all nodes in a queue, + * without dequeuing them. + * @head: head of the queue (struct cds_wfcq_head or __cds_wfcq_head pointer). + * @tail: tail of the queue (struct cds_wfcq_tail pointer). + * @node: iterator on the queue (struct cds_wfcq_node pointer). + * + * Content written into each node before enqueue is guaranteed to be + * consistent, but no other memory ordering is ensured. + * Dequeue/splice/iteration mutual exclusion should be ensured by the + * caller. + */ +#define __cds_wfcq_for_each_blocking(head, tail, node) \ + for (node = __cds_wfcq_first_blocking(head, tail); \ + node != NULL; \ + node = __cds_wfcq_next_blocking(head, tail, node)) + +/* + * __cds_wfcq_for_each_blocking_safe: Iterate over all nodes in a queue, + * without dequeuing them. Safe against deletion. + * @head: head of the queue (struct cds_wfcq_head or __cds_wfcq_head pointer). + * @tail: tail of the queue (struct cds_wfcq_tail pointer). + * @node: iterator on the queue (struct cds_wfcq_node pointer). + * @n: struct cds_wfcq_node pointer holding the next pointer (used + * internally). + * + * Content written into each node before enqueue is guaranteed to be + * consistent, but no other memory ordering is ensured. + * Dequeue/splice/iteration mutual exclusion should be ensured by the + * caller. + */ +#define __cds_wfcq_for_each_blocking_safe(head, tail, node, n) \ + for (node = __cds_wfcq_first_blocking(head, tail), \ + n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL); \ + node != NULL; \ + node = n, n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL)) + +#ifdef __cplusplus +} +#endif + +#endif /* _URCU_WFCQUEUE_H */