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1 | /* | |
2 | * coroutine queues and locks | |
3 | * | |
4 | * Copyright (c) 2011 Kevin Wolf <kwolf@redhat.com> | |
5 | * | |
6 | * Permission is hereby granted, free of charge, to any person obtaining a copy | |
7 | * of this software and associated documentation files (the "Software"), to deal | |
8 | * in the Software without restriction, including without limitation the rights | |
9 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
10 | * copies of the Software, and to permit persons to whom the Software is | |
11 | * furnished to do so, subject to the following conditions: | |
12 | * | |
13 | * The above copyright notice and this permission notice shall be included in | |
14 | * all copies or substantial portions of the Software. | |
15 | * | |
16 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
17 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
18 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL | |
19 | * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
20 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
21 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | |
22 | * THE SOFTWARE. | |
23 | */ | |
24 | ||
25 | #include "qemu-common.h" | |
26 | #include "block/coroutine.h" | |
27 | #include "block/coroutine_int.h" | |
28 | #include "qemu/queue.h" | |
29 | #include "block/aio.h" | |
30 | #include "trace.h" | |
31 | ||
32 | /* Coroutines are awoken from a BH to allow the current coroutine to complete | |
33 | * its flow of execution. The BH may run after the CoQueue has been destroyed, | |
34 | * so keep BH data in a separate heap-allocated struct. | |
35 | */ | |
36 | typedef struct { | |
37 | QEMUBH *bh; | |
38 | QTAILQ_HEAD(, Coroutine) entries; | |
39 | } CoQueueNextData; | |
40 | ||
41 | static void qemu_co_queue_next_bh(void *opaque) | |
42 | { | |
43 | CoQueueNextData *data = opaque; | |
44 | Coroutine *next; | |
45 | ||
46 | trace_qemu_co_queue_next_bh(); | |
47 | while ((next = QTAILQ_FIRST(&data->entries))) { | |
48 | QTAILQ_REMOVE(&data->entries, next, co_queue_next); | |
49 | qemu_coroutine_enter(next, NULL); | |
50 | } | |
51 | ||
52 | qemu_bh_delete(data->bh); | |
53 | g_slice_free(CoQueueNextData, data); | |
54 | } | |
55 | ||
56 | void qemu_co_queue_init(CoQueue *queue) | |
57 | { | |
58 | QTAILQ_INIT(&queue->entries); | |
59 | ||
60 | /* This will be exposed to callers once there are multiple AioContexts */ | |
61 | queue->ctx = qemu_get_aio_context(); | |
62 | } | |
63 | ||
64 | void coroutine_fn qemu_co_queue_wait(CoQueue *queue) | |
65 | { | |
66 | Coroutine *self = qemu_coroutine_self(); | |
67 | QTAILQ_INSERT_TAIL(&queue->entries, self, co_queue_next); | |
68 | qemu_coroutine_yield(); | |
69 | assert(qemu_in_coroutine()); | |
70 | } | |
71 | ||
72 | void coroutine_fn qemu_co_queue_wait_insert_head(CoQueue *queue) | |
73 | { | |
74 | Coroutine *self = qemu_coroutine_self(); | |
75 | QTAILQ_INSERT_HEAD(&queue->entries, self, co_queue_next); | |
76 | qemu_coroutine_yield(); | |
77 | assert(qemu_in_coroutine()); | |
78 | } | |
79 | ||
80 | static bool qemu_co_queue_do_restart(CoQueue *queue, bool single) | |
81 | { | |
82 | Coroutine *next; | |
83 | CoQueueNextData *data; | |
84 | ||
85 | if (QTAILQ_EMPTY(&queue->entries)) { | |
86 | return false; | |
87 | } | |
88 | ||
89 | data = g_slice_new(CoQueueNextData); | |
90 | data->bh = aio_bh_new(queue->ctx, qemu_co_queue_next_bh, data); | |
91 | QTAILQ_INIT(&data->entries); | |
92 | qemu_bh_schedule(data->bh); | |
93 | ||
94 | while ((next = QTAILQ_FIRST(&queue->entries)) != NULL) { | |
95 | QTAILQ_REMOVE(&queue->entries, next, co_queue_next); | |
96 | QTAILQ_INSERT_TAIL(&data->entries, next, co_queue_next); | |
97 | trace_qemu_co_queue_next(next); | |
98 | if (single) { | |
99 | break; | |
100 | } | |
101 | } | |
102 | return true; | |
103 | } | |
104 | ||
105 | bool qemu_co_queue_next(CoQueue *queue) | |
106 | { | |
107 | return qemu_co_queue_do_restart(queue, true); | |
108 | } | |
109 | ||
110 | void qemu_co_queue_restart_all(CoQueue *queue) | |
111 | { | |
112 | qemu_co_queue_do_restart(queue, false); | |
113 | } | |
114 | ||
115 | bool qemu_co_queue_empty(CoQueue *queue) | |
116 | { | |
117 | return (QTAILQ_FIRST(&queue->entries) == NULL); | |
118 | } | |
119 | ||
120 | void qemu_co_mutex_init(CoMutex *mutex) | |
121 | { | |
122 | memset(mutex, 0, sizeof(*mutex)); | |
123 | qemu_co_queue_init(&mutex->queue); | |
124 | } | |
125 | ||
126 | void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex) | |
127 | { | |
128 | Coroutine *self = qemu_coroutine_self(); | |
129 | ||
130 | trace_qemu_co_mutex_lock_entry(mutex, self); | |
131 | ||
132 | while (mutex->locked) { | |
133 | qemu_co_queue_wait(&mutex->queue); | |
134 | } | |
135 | ||
136 | mutex->locked = true; | |
137 | ||
138 | trace_qemu_co_mutex_lock_return(mutex, self); | |
139 | } | |
140 | ||
141 | void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex) | |
142 | { | |
143 | Coroutine *self = qemu_coroutine_self(); | |
144 | ||
145 | trace_qemu_co_mutex_unlock_entry(mutex, self); | |
146 | ||
147 | assert(mutex->locked == true); | |
148 | assert(qemu_in_coroutine()); | |
149 | ||
150 | mutex->locked = false; | |
151 | qemu_co_queue_next(&mutex->queue); | |
152 | ||
153 | trace_qemu_co_mutex_unlock_return(mutex, self); | |
154 | } | |
155 | ||
156 | void qemu_co_rwlock_init(CoRwlock *lock) | |
157 | { | |
158 | memset(lock, 0, sizeof(*lock)); | |
159 | qemu_co_queue_init(&lock->queue); | |
160 | } | |
161 | ||
162 | void qemu_co_rwlock_rdlock(CoRwlock *lock) | |
163 | { | |
164 | while (lock->writer) { | |
165 | qemu_co_queue_wait(&lock->queue); | |
166 | } | |
167 | lock->reader++; | |
168 | } | |
169 | ||
170 | void qemu_co_rwlock_unlock(CoRwlock *lock) | |
171 | { | |
172 | assert(qemu_in_coroutine()); | |
173 | if (lock->writer) { | |
174 | lock->writer = false; | |
175 | qemu_co_queue_restart_all(&lock->queue); | |
176 | } else { | |
177 | lock->reader--; | |
178 | assert(lock->reader >= 0); | |
179 | /* Wakeup only one waiting writer */ | |
180 | if (!lock->reader) { | |
181 | qemu_co_queue_next(&lock->queue); | |
182 | } | |
183 | } | |
184 | } | |
185 | ||
186 | void qemu_co_rwlock_wrlock(CoRwlock *lock) | |
187 | { | |
188 | while (lock->writer || lock->reader) { | |
189 | qemu_co_queue_wait(&lock->queue); | |
190 | } | |
191 | lock->writer = true; | |
192 | } |