Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging
[qemu.git] / async.c
1 /*
2 * QEMU System Emulator
3 *
4 * Copyright (c) 2003-2008 Fabrice Bellard
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/aio.h"
27 #include "block/thread-pool.h"
28 #include "qemu/main-loop.h"
29
30 /***********************************************************/
31 /* bottom halves (can be seen as timers which expire ASAP) */
32
33 struct QEMUBH {
34 AioContext *ctx;
35 QEMUBHFunc *cb;
36 void *opaque;
37 QEMUBH *next;
38 bool scheduled;
39 bool idle;
40 bool deleted;
41 };
42
43 QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
44 {
45 QEMUBH *bh;
46 bh = g_malloc0(sizeof(QEMUBH));
47 bh->ctx = ctx;
48 bh->cb = cb;
49 bh->opaque = opaque;
50 qemu_mutex_lock(&ctx->bh_lock);
51 bh->next = ctx->first_bh;
52 /* Make sure that the members are ready before putting bh into list */
53 smp_wmb();
54 ctx->first_bh = bh;
55 qemu_mutex_unlock(&ctx->bh_lock);
56 return bh;
57 }
58
59 /* Multiple occurrences of aio_bh_poll cannot be called concurrently */
60 int aio_bh_poll(AioContext *ctx)
61 {
62 QEMUBH *bh, **bhp, *next;
63 int ret;
64
65 ctx->walking_bh++;
66
67 ret = 0;
68 for (bh = ctx->first_bh; bh; bh = next) {
69 /* Make sure that fetching bh happens before accessing its members */
70 smp_read_barrier_depends();
71 next = bh->next;
72 if (!bh->deleted && bh->scheduled) {
73 bh->scheduled = 0;
74 /* Paired with write barrier in bh schedule to ensure reading for
75 * idle & callbacks coming after bh's scheduling.
76 */
77 smp_rmb();
78 if (!bh->idle)
79 ret = 1;
80 bh->idle = 0;
81 bh->cb(bh->opaque);
82 }
83 }
84
85 ctx->walking_bh--;
86
87 /* remove deleted bhs */
88 if (!ctx->walking_bh) {
89 qemu_mutex_lock(&ctx->bh_lock);
90 bhp = &ctx->first_bh;
91 while (*bhp) {
92 bh = *bhp;
93 if (bh->deleted) {
94 *bhp = bh->next;
95 g_free(bh);
96 } else {
97 bhp = &bh->next;
98 }
99 }
100 qemu_mutex_unlock(&ctx->bh_lock);
101 }
102
103 return ret;
104 }
105
106 void qemu_bh_schedule_idle(QEMUBH *bh)
107 {
108 if (bh->scheduled)
109 return;
110 bh->idle = 1;
111 /* Make sure that idle & any writes needed by the callback are done
112 * before the locations are read in the aio_bh_poll.
113 */
114 smp_wmb();
115 bh->scheduled = 1;
116 }
117
118 void qemu_bh_schedule(QEMUBH *bh)
119 {
120 if (bh->scheduled)
121 return;
122 bh->idle = 0;
123 /* Make sure that idle & any writes needed by the callback are done
124 * before the locations are read in the aio_bh_poll.
125 */
126 smp_wmb();
127 bh->scheduled = 1;
128 aio_notify(bh->ctx);
129 }
130
131
132 /* This func is async.
133 */
134 void qemu_bh_cancel(QEMUBH *bh)
135 {
136 bh->scheduled = 0;
137 }
138
139 /* This func is async.The bottom half will do the delete action at the finial
140 * end.
141 */
142 void qemu_bh_delete(QEMUBH *bh)
143 {
144 bh->scheduled = 0;
145 bh->deleted = 1;
146 }
147
148 static gboolean
149 aio_ctx_prepare(GSource *source, gint *timeout)
150 {
151 AioContext *ctx = (AioContext *) source;
152 QEMUBH *bh;
153 int deadline;
154
155 /* We assume there is no timeout already supplied */
156 *timeout = -1;
157 for (bh = ctx->first_bh; bh; bh = bh->next) {
158 if (!bh->deleted && bh->scheduled) {
159 if (bh->idle) {
160 /* idle bottom halves will be polled at least
161 * every 10ms */
162 *timeout = 10;
163 } else {
164 /* non-idle bottom halves will be executed
165 * immediately */
166 *timeout = 0;
167 return true;
168 }
169 }
170 }
171
172 deadline = qemu_timeout_ns_to_ms(timerlistgroup_deadline_ns(&ctx->tlg));
173 if (deadline == 0) {
174 *timeout = 0;
175 return true;
176 } else {
177 *timeout = qemu_soonest_timeout(*timeout, deadline);
178 }
179
180 return false;
181 }
182
183 static gboolean
184 aio_ctx_check(GSource *source)
185 {
186 AioContext *ctx = (AioContext *) source;
187 QEMUBH *bh;
188
189 for (bh = ctx->first_bh; bh; bh = bh->next) {
190 if (!bh->deleted && bh->scheduled) {
191 return true;
192 }
193 }
194 return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
195 }
196
197 static gboolean
198 aio_ctx_dispatch(GSource *source,
199 GSourceFunc callback,
200 gpointer user_data)
201 {
202 AioContext *ctx = (AioContext *) source;
203
204 assert(callback == NULL);
205 aio_poll(ctx, false);
206 return true;
207 }
208
209 static void
210 aio_ctx_finalize(GSource *source)
211 {
212 AioContext *ctx = (AioContext *) source;
213
214 thread_pool_free(ctx->thread_pool);
215 aio_set_event_notifier(ctx, &ctx->notifier, NULL);
216 event_notifier_cleanup(&ctx->notifier);
217 rfifolock_destroy(&ctx->lock);
218 qemu_mutex_destroy(&ctx->bh_lock);
219 g_array_free(ctx->pollfds, TRUE);
220 timerlistgroup_deinit(&ctx->tlg);
221 }
222
223 static GSourceFuncs aio_source_funcs = {
224 aio_ctx_prepare,
225 aio_ctx_check,
226 aio_ctx_dispatch,
227 aio_ctx_finalize
228 };
229
230 GSource *aio_get_g_source(AioContext *ctx)
231 {
232 g_source_ref(&ctx->source);
233 return &ctx->source;
234 }
235
236 ThreadPool *aio_get_thread_pool(AioContext *ctx)
237 {
238 if (!ctx->thread_pool) {
239 ctx->thread_pool = thread_pool_new(ctx);
240 }
241 return ctx->thread_pool;
242 }
243
244 void aio_notify(AioContext *ctx)
245 {
246 event_notifier_set(&ctx->notifier);
247 }
248
249 static void aio_timerlist_notify(void *opaque)
250 {
251 aio_notify(opaque);
252 }
253
254 static void aio_rfifolock_cb(void *opaque)
255 {
256 /* Kick owner thread in case they are blocked in aio_poll() */
257 aio_notify(opaque);
258 }
259
260 AioContext *aio_context_new(void)
261 {
262 AioContext *ctx;
263 ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
264 ctx->pollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
265 ctx->thread_pool = NULL;
266 qemu_mutex_init(&ctx->bh_lock);
267 rfifolock_init(&ctx->lock, aio_rfifolock_cb, ctx);
268 event_notifier_init(&ctx->notifier, false);
269 aio_set_event_notifier(ctx, &ctx->notifier,
270 (EventNotifierHandler *)
271 event_notifier_test_and_clear);
272 timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
273
274 return ctx;
275 }
276
277 void aio_context_ref(AioContext *ctx)
278 {
279 g_source_ref(&ctx->source);
280 }
281
282 void aio_context_unref(AioContext *ctx)
283 {
284 g_source_unref(&ctx->source);
285 }
286
287 void aio_context_acquire(AioContext *ctx)
288 {
289 rfifolock_lock(&ctx->lock);
290 }
291
292 void aio_context_release(AioContext *ctx)
293 {
294 rfifolock_unlock(&ctx->lock);
295 }