Cleanup: update code layout to fix old gcc warning
[urcu.git] / src / urcu-wait.h
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1#ifndef _URCU_WAIT_H
2#define _URCU_WAIT_H
3
4/*
5 * urcu-wait.h
6 *
7 * Userspace RCU library wait/wakeup management
8 *
9 * Copyright (c) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
10 *
11 * This library is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU Lesser General Public
13 * License as published by the Free Software Foundation; either
14 * version 2.1 of the License, or (at your option) any later version.
15 *
16 * This library is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 * Lesser General Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser General Public
22 * License along with this library; if not, write to the Free Software
23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 */
25
26#include <urcu/uatomic.h>
bf6822a6 27#include <urcu/wfstack.h>
b0a841b4 28#include "urcu-die.h"
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29
30/*
31 * Number of busy-loop attempts before waiting on futex for grace period
32 * batching.
33 */
34#define URCU_WAIT_ATTEMPTS 1000
35
36enum urcu_wait_state {
37 /* URCU_WAIT_WAITING is compared directly (futex compares it). */
38 URCU_WAIT_WAITING = 0,
39 /* non-zero are used as masks. */
40 URCU_WAIT_WAKEUP = (1 << 0),
bf6822a6 41 URCU_WAIT_RUNNING = (1 << 1),
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42 URCU_WAIT_TEARDOWN = (1 << 2),
43};
44
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45struct urcu_wait_node {
46 struct cds_wfs_node node;
47 int32_t state; /* enum urcu_wait_state */
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48};
49
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50#define URCU_WAIT_NODE_INIT(name, _state) \
51 { .state = _state }
52
53#define DEFINE_URCU_WAIT_NODE(name, state) \
54 struct urcu_wait_node name = URCU_WAIT_NODE_INIT(name, state)
55
56#define DECLARE_URCU_WAIT_NODE(name) \
57 struct urcu_wait_node name
58
59struct urcu_wait_queue {
60 struct cds_wfs_stack stack;
61};
62
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63#define URCU_WAIT_QUEUE_HEAD_INIT(name) \
64 { \
65 .stack = { \
66 .head = CDS_WFS_END, \
67 .lock = PTHREAD_MUTEX_INITIALIZER, \
68 }, \
69 }
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70
71#define DECLARE_URCU_WAIT_QUEUE(name) \
72 struct urcu_wait_queue name
73
74#define DEFINE_URCU_WAIT_QUEUE(name) \
75 struct urcu_wait_queue name = URCU_WAIT_QUEUE_HEAD_INIT(name)
76
77struct urcu_waiters {
78 struct cds_wfs_head *head;
79};
80
81/*
82 * Add ourself atomically to a wait queue. Return 0 if queue was
83 * previously empty, else return 1.
84 * A full memory barrier is issued before being added to the wait queue.
85 */
86static inline
87bool urcu_wait_add(struct urcu_wait_queue *queue,
88 struct urcu_wait_node *node)
89{
90 return cds_wfs_push(&queue->stack, &node->node);
91}
92
93/*
94 * Atomically move all waiters from wait queue into our local struct
95 * urcu_waiters.
96 */
97static inline
98void urcu_move_waiters(struct urcu_waiters *waiters,
99 struct urcu_wait_queue *queue)
100{
101 waiters->head = __cds_wfs_pop_all(&queue->stack);
102}
103
104static inline
105void urcu_wait_set_state(struct urcu_wait_node *node,
106 enum urcu_wait_state state)
107{
108 node->state = state;
109}
110
cba82d7b 111static inline
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112void urcu_wait_node_init(struct urcu_wait_node *node,
113 enum urcu_wait_state state)
cba82d7b 114{
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115 urcu_wait_set_state(node, state);
116 cds_wfs_node_init(&node->node);
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117}
118
119/*
120 * Note: urcu_adaptative_wake_up needs "value" to stay allocated
bf6822a6 121 * throughout its execution. In this scheme, the waiter owns the node
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122 * memory, and we only allow it to free this memory when it receives the
123 * URCU_WAIT_TEARDOWN flag.
124 */
125static inline
bf6822a6 126void urcu_adaptative_wake_up(struct urcu_wait_node *wait)
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127{
128 cmm_smp_mb();
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129 assert(uatomic_read(&wait->state) == URCU_WAIT_WAITING);
130 uatomic_set(&wait->state, URCU_WAIT_WAKEUP);
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131 if (!(uatomic_read(&wait->state) & URCU_WAIT_RUNNING)) {
132 if (futex_noasync(&wait->state, FUTEX_WAKE, 1,
133 NULL, NULL, 0) < 0)
134 urcu_die(errno);
135 }
cba82d7b 136 /* Allow teardown of struct urcu_wait memory. */
bf6822a6 137 uatomic_or(&wait->state, URCU_WAIT_TEARDOWN);
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138}
139
140/*
141 * Caller must initialize "value" to URCU_WAIT_WAITING before passing its
142 * memory to waker thread.
143 */
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144static inline
145void urcu_adaptative_busy_wait(struct urcu_wait_node *wait)
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146{
147 unsigned int i;
148
bf6822a6 149 /* Load and test condition before read state */
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150 cmm_smp_rmb();
151 for (i = 0; i < URCU_WAIT_ATTEMPTS; i++) {
bf6822a6 152 if (uatomic_read(&wait->state) != URCU_WAIT_WAITING)
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153 goto skip_futex_wait;
154 caa_cpu_relax();
155 }
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156 while (futex_noasync(&wait->state, FUTEX_WAIT, URCU_WAIT_WAITING,
157 NULL, NULL, 0)) {
158 switch (errno) {
159 case EWOULDBLOCK:
160 /* Value already changed. */
161 goto skip_futex_wait;
162 case EINTR:
163 /* Retry if interrupted by signal. */
164 break; /* Get out of switch. */
165 default:
166 /* Unexpected error. */
167 urcu_die(errno);
168 }
169 }
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170skip_futex_wait:
171
ffa11a18 172 /* Tell waker thread than we are running. */
bf6822a6 173 uatomic_or(&wait->state, URCU_WAIT_RUNNING);
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174
175 /*
176 * Wait until waker thread lets us know it's ok to tear down
177 * memory allocated for struct urcu_wait.
178 */
179 for (i = 0; i < URCU_WAIT_ATTEMPTS; i++) {
bf6822a6 180 if (uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN)
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181 break;
182 caa_cpu_relax();
183 }
bf6822a6 184 while (!(uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN))
cba82d7b 185 poll(NULL, 0, 10);
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186 assert(uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN);
187}
188
189static inline
190void urcu_wake_all_waiters(struct urcu_waiters *waiters)
191{
192 struct cds_wfs_node *iter, *iter_n;
193
194 /* Wake all waiters in our stack head */
195 cds_wfs_for_each_blocking_safe(waiters->head, iter, iter_n) {
196 struct urcu_wait_node *wait_node =
197 caa_container_of(iter, struct urcu_wait_node, node);
198
199 /* Don't wake already running threads */
200 if (wait_node->state & URCU_WAIT_RUNNING)
201 continue;
202 urcu_adaptative_wake_up(wait_node);
203 }
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204}
205
206#endif /* _URCU_WAIT_H */
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