[userspace-rcu.git] / urcu / static / wfstack.h

#ifndef _URCU_WFSTACK_STATIC_H
#define _URCU_WFSTACK_STATIC_H

/*
 * wfstack-static.h
 *
 * Userspace RCU library - Stack with Wait-Free push, Blocking pop.
 *
 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See wfstack.h for linking
 * dynamically with the userspace rcu library.
 *
 * Copyright 2010 - 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 <pthread.h>
#include <assert.h>
#include <poll.h>
#include <urcu/compiler.h>
#include <urcu/uatomic.h>

#ifdef __cplusplus
extern "C" {
#endif

#define CDS_WF_STACK_END			((void *)0x1UL)
#define CDS_WFS_ADAPT_ATTEMPTS		10	/* Retry if being set */
#define CDS_WFS_WAIT			10	/* Wait 10 ms if being set */

static inline
void _cds_wfs_node_init(struct cds_wfs_node *node)
{
	node->next = NULL;
}

static inline
void _cds_wfs_init(struct cds_wfs_stack *s)
{
	int ret;

	s->head = CDS_WF_STACK_END;
	ret = pthread_mutex_init(&s->lock, NULL);
	assert(!ret);
}

static inline
void _cds_wfs_push(struct cds_wfs_stack *s, struct cds_wfs_node *node)
{
	struct cds_wfs_node *old_head;

	assert(node->next == NULL);
	/*
	 * uatomic_xchg() implicit memory barrier orders earlier stores to node
	 * (setting it to NULL) before publication.
	 */
	old_head = uatomic_xchg(&s->head, node);
	/*
	 * 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);
}

/*
 * Returns NULL if stack is empty.
 */
static inline
struct cds_wfs_node *
___cds_wfs_pop_blocking(struct cds_wfs_stack *s)
{
	struct cds_wfs_node *head, *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) {
		if (++attempt >= CDS_WFS_ADAPT_ATTEMPTS) {
			poll(NULL, 0, CDS_WFS_WAIT);	/* Wait for 10ms */
			attempt = 0;
		} else
			caa_cpu_relax();
	}
	if (uatomic_cmpxchg(&s->head, head, next) == head)
		return head;
	else
		goto retry;		/* Concurrent modification. Retry. */
}

static inline
struct cds_wfs_node *
_cds_wfs_pop_blocking(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);
	ret = pthread_mutex_unlock(&s->lock);
	assert(!ret);
	return retnode;
}

#ifdef __cplusplus
}
#endif

#endif /* _URCU_WFSTACK_STATIC_H */
Commit	Line	Data
	1	#ifndef _URCU_WFSTACK_STATIC_H
	2	#define _URCU_WFSTACK_STATIC_H
	3
	4	/*
	5	* wfstack-static.h
	6	*
	7	* Userspace RCU library - Stack with Wait-Free push, Blocking pop.
	8	*
	9	* TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See wfstack.h for linking
	10	* dynamically with the userspace rcu library.
	11	*
	12	* Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	13	*
	14	* This library is free software; you can redistribute it and/or
	15	* modify it under the terms of the GNU Lesser General Public
	16	* License as published by the Free Software Foundation; either
	17	* version 2.1 of the License, or (at your option) any later version.
	18	*
	19	* This library is distributed in the hope that it will be useful,
	20	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	21	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	22	* Lesser General Public License for more details.
	23	*
	24	* You should have received a copy of the GNU Lesser General Public
	25	* License along with this library; if not, write to the Free Software
	26	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	27	*/
	28
	29	#include <pthread.h>
	30	#include <assert.h>
	31	#include <poll.h>
	32	#include <urcu/compiler.h>
	33	#include <urcu/uatomic.h>
	34
	35	#ifdef __cplusplus
	36	extern "C" {
	37	#endif
	38
	39	#define CDS_WF_STACK_END ((void *)0x1UL)
	40	#define CDS_WFS_ADAPT_ATTEMPTS 10 /* Retry if being set */
	41	#define CDS_WFS_WAIT 10 /* Wait 10 ms if being set */
	42
	43	static inline
	44	void _cds_wfs_node_init(struct cds_wfs_node *node)
	45	{
	46	node->next = NULL;
	47	}
	48
	49	static inline
	50	void _cds_wfs_init(struct cds_wfs_stack *s)
	51	{
	52	int ret;
	53
	54	s->head = CDS_WF_STACK_END;
	55	ret = pthread_mutex_init(&s->lock, NULL);
	56	assert(!ret);
	57	}
	58
	59	static inline
	60	void _cds_wfs_push(struct cds_wfs_stack s, struct cds_wfs_node node)
	61	{
	62	struct cds_wfs_node *old_head;
	63
	64	assert(node->next == NULL);
	65	/*
	66	* uatomic_xchg() implicit memory barrier orders earlier stores to node
	67	* (setting it to NULL) before publication.
	68	*/
	69	old_head = uatomic_xchg(&s->head, node);
	70	/*
	71	* At this point, dequeuers see a NULL node->next, they should busy-wait
	72	* until node->next is set to old_head.
	73	*/
	74	CMM_STORE_SHARED(node->next, old_head);
	75	}
	76
	77	/*
	78	* Returns NULL if stack is empty.
	79	*/
	80	static inline
	81	struct cds_wfs_node *
	82	___cds_wfs_pop_blocking(struct cds_wfs_stack *s)
	83	{
	84	struct cds_wfs_node head, next;
	85	int attempt = 0;
	86
	87	retry:
	88	head = CMM_LOAD_SHARED(s->head);
	89	if (head == CDS_WF_STACK_END)
	90	return NULL;
	91	/*
	92	* Adaptative busy-looping waiting for push to complete.
	93	*/
	94	while ((next = CMM_LOAD_SHARED(head->next)) == NULL) {
	95	if (++attempt >= CDS_WFS_ADAPT_ATTEMPTS) {
	96	poll(NULL, 0, CDS_WFS_WAIT); /* Wait for 10ms */
	97	attempt = 0;
	98	} else
	99	caa_cpu_relax();
	100	}
	101	if (uatomic_cmpxchg(&s->head, head, next) == head)
	102	return head;
	103	else
	104	goto retry; /* Concurrent modification. Retry. */
	105	}
	106
	107	static inline
	108	struct cds_wfs_node *
	109	_cds_wfs_pop_blocking(struct cds_wfs_stack *s)
	110	{
	111	struct cds_wfs_node *retnode;
	112	int ret;
	113
	114	ret = pthread_mutex_lock(&s->lock);
	115	assert(!ret);
	116	retnode = ___cds_wfs_pop_blocking(s);
	117	ret = pthread_mutex_unlock(&s->lock);
	118	assert(!ret);
	119	return retnode;
	120	}
	121
	122	#ifdef __cplusplus
	123	}
	124	#endif
	125
	126	#endif /* _URCU_WFSTACK_STATIC_H */