Commit | Line | Data |
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453629a9 MD |
1 | /* |
2 | * rculfstack.h | |
3 | * | |
4 | * Userspace RCU library - Lock-Free RCU Stack | |
5 | * | |
6 | * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
7 | * | |
8 | * This library is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU Lesser General Public | |
10 | * License as published by the Free Software Foundation; either | |
11 | * version 2.1 of the License, or (at your option) any later version. | |
12 | * | |
13 | * This library is distributed in the hope that it will be useful, | |
14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | * Lesser General Public License for more details. | |
17 | * | |
18 | * You should have received a copy of the GNU Lesser General Public | |
19 | * License along with this library; if not, write to the Free Software | |
20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
21 | */ | |
22 | ||
23 | #if (!defined(_GNU_SOURCE) && !defined(_LGPL_SOURCE)) | |
24 | #error "Dynamic loader LGPL wrappers not implemented yet" | |
25 | #endif | |
26 | ||
27 | struct rcu_lfs_node { | |
28 | struct rcu_lfs_node *next; | |
29 | }; | |
30 | ||
31 | struct rcu_lfs_stack { | |
32 | struct rcu_lfs_node *head; | |
33 | }; | |
34 | ||
35 | void rcu_lfs_node_init(struct rcu_lfs_node *node) | |
36 | { | |
37 | } | |
38 | ||
39 | void rcu_lfs_init(struct rcu_lfs_stack *s) | |
40 | { | |
41 | s->head = NULL; | |
42 | } | |
43 | ||
44 | void rcu_lfs_push(struct rcu_lfs_stack *s, struct rcu_lfs_node *node) | |
45 | { | |
453629a9 | 46 | for (;;) { |
2e6c6432 | 47 | struct rcu_lfs_node *head; |
453629a9 | 48 | |
2e6c6432 MD |
49 | rcu_read_lock(); |
50 | head = rcu_dereference(s->head); | |
453629a9 MD |
51 | node->next = head; |
52 | /* | |
53 | * uatomic_cmpxchg() implicit memory barrier orders earlier | |
54 | * stores to node before publication. | |
55 | */ | |
56 | if (uatomic_cmpxchg(&s->head, head, node) == head) { | |
57 | rcu_read_unlock(); | |
58 | return; | |
59 | } else { | |
60 | /* Failure to prepend. Retry. */ | |
2e6c6432 | 61 | rcu_read_unlock(); |
453629a9 MD |
62 | continue; |
63 | } | |
64 | } | |
65 | } | |
66 | ||
1c1e940e MD |
67 | /* |
68 | * The caller must wait for a grace period to pass before freeing the returned | |
69 | * node. | |
70 | * Returns NULL if stack is empty. | |
71 | */ | |
453629a9 MD |
72 | struct rcu_lfs_node * |
73 | rcu_lfs_pop(struct rcu_lfs_stack *s) | |
74 | { | |
453629a9 | 75 | for (;;) { |
2e6c6432 | 76 | struct rcu_lfs_node *head; |
453629a9 | 77 | |
2e6c6432 MD |
78 | rcu_read_lock(); |
79 | head = rcu_dereference(s->head); | |
453629a9 MD |
80 | if (head) { |
81 | struct rcu_lfs_node *next = rcu_dereference(head->next); | |
82 | ||
83 | if (uatomic_cmpxchg(&s->head, head, next) == head) { | |
84 | rcu_read_unlock(); | |
85 | return head; | |
86 | } else { | |
87 | /* Concurrent modification. Retry. */ | |
2e6c6432 | 88 | rcu_read_unlock(); |
453629a9 MD |
89 | continue; |
90 | } | |
91 | } else { | |
92 | /* Empty stack */ | |
93 | rcu_read_unlock(); | |
94 | return NULL; | |
95 | } | |
96 | } | |
97 | } |