1 #ifndef _URCU_WFSTACK_STATIC_H
2 #define _URCU_WFSTACK_STATIC_H
7 * Userspace RCU library - Stack with Wait-Free push, Blocking pop.
9 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See wfstack.h for linking
10 * dynamically with the userspace rcu library.
12 * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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.
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.
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
32 #include <urcu/compiler.h>
33 #include <urcu/uatomic.h>
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 */
44 void _cds_wfs_node_init(struct cds_wfs_node
*node
)
50 void _cds_wfs_init(struct cds_wfs_stack
*s
)
54 s
->head
= CDS_WF_STACK_END
;
55 ret
= pthread_mutex_init(&s
->lock
, NULL
);
60 * Returns 0 if stack was empty, 1 otherwise.
63 int _cds_wfs_push(struct cds_wfs_stack
*s
, struct cds_wfs_node
*node
)
65 struct cds_wfs_node
*old_head
;
67 assert(node
->next
== NULL
);
69 * uatomic_xchg() implicit memory barrier orders earlier stores to node
70 * (setting it to NULL) before publication.
72 old_head
= uatomic_xchg(&s
->head
, node
);
74 * At this point, dequeuers see a NULL node->next, they should busy-wait
75 * until node->next is set to old_head.
77 CMM_STORE_SHARED(node
->next
, old_head
);
78 return (old_head
!= CDS_WF_STACK_END
);
82 * Returns NULL if stack is empty.
86 ___cds_wfs_pop_blocking(struct cds_wfs_stack
*s
)
88 struct cds_wfs_node
*head
, *next
;
92 head
= CMM_LOAD_SHARED(s
->head
);
93 if (head
== CDS_WF_STACK_END
)
96 * Adaptative busy-looping waiting for push to complete.
98 while ((next
= CMM_LOAD_SHARED(head
->next
)) == NULL
) {
99 if (++attempt
>= CDS_WFS_ADAPT_ATTEMPTS
) {
100 poll(NULL
, 0, CDS_WFS_WAIT
); /* Wait for 10ms */
105 if (uatomic_cmpxchg(&s
->head
, head
, next
) == head
)
108 goto retry
; /* Concurrent modification. Retry. */
112 struct cds_wfs_node
*
113 _cds_wfs_pop_blocking(struct cds_wfs_stack
*s
)
115 struct cds_wfs_node
*retnode
;
118 ret
= pthread_mutex_lock(&s
->lock
);
120 retnode
= ___cds_wfs_pop_blocking(s
);
121 ret
= pthread_mutex_unlock(&s
->lock
);
130 #endif /* _URCU_WFSTACK_STATIC_H */
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