tests: virtio-9p: code refactoring
[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/osdep.h"
26 #include "qapi/error.h"
27 #include "qemu-common.h"
28 #include "block/aio.h"
29 #include "block/thread-pool.h"
30 #include "qemu/main-loop.h"
31 #include "qemu/atomic.h"
32 #include "block/raw-aio.h"
33
34 /***********************************************************/
35 /* bottom halves (can be seen as timers which expire ASAP) */
36
37 struct QEMUBH {
38 AioContext *ctx;
39 QEMUBHFunc *cb;
40 void *opaque;
41 QEMUBH *next;
42 bool scheduled;
43 bool idle;
44 bool deleted;
45 };
46
47 void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
48 {
49 QEMUBH *bh;
50 bh = g_new(QEMUBH, 1);
51 *bh = (QEMUBH){
52 .ctx = ctx,
53 .cb = cb,
54 .opaque = opaque,
55 };
56 qemu_mutex_lock(&ctx->bh_lock);
57 bh->next = ctx->first_bh;
58 bh->scheduled = 1;
59 bh->deleted = 1;
60 /* Make sure that the members are ready before putting bh into list */
61 smp_wmb();
62 ctx->first_bh = bh;
63 qemu_mutex_unlock(&ctx->bh_lock);
64 aio_notify(ctx);
65 }
66
67 QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
68 {
69 QEMUBH *bh;
70 bh = g_new(QEMUBH, 1);
71 *bh = (QEMUBH){
72 .ctx = ctx,
73 .cb = cb,
74 .opaque = opaque,
75 };
76 qemu_mutex_lock(&ctx->bh_lock);
77 bh->next = ctx->first_bh;
78 /* Make sure that the members are ready before putting bh into list */
79 smp_wmb();
80 ctx->first_bh = bh;
81 qemu_mutex_unlock(&ctx->bh_lock);
82 return bh;
83 }
84
85 void aio_bh_call(QEMUBH *bh)
86 {
87 bh->cb(bh->opaque);
88 }
89
90 /* Multiple occurrences of aio_bh_poll cannot be called concurrently */
91 int aio_bh_poll(AioContext *ctx)
92 {
93 QEMUBH *bh, **bhp, *next;
94 int ret;
95
96 ctx->walking_bh++;
97
98 ret = 0;
99 for (bh = ctx->first_bh; bh; bh = next) {
100 /* Make sure that fetching bh happens before accessing its members */
101 smp_read_barrier_depends();
102 next = bh->next;
103 /* The atomic_xchg is paired with the one in qemu_bh_schedule. The
104 * implicit memory barrier ensures that the callback sees all writes
105 * done by the scheduling thread. It also ensures that the scheduling
106 * thread sees the zero before bh->cb has run, and thus will call
107 * aio_notify again if necessary.
108 */
109 if (atomic_xchg(&bh->scheduled, 0)) {
110 /* Idle BHs don't count as progress */
111 if (!bh->idle) {
112 ret = 1;
113 }
114 bh->idle = 0;
115 aio_bh_call(bh);
116 }
117 }
118
119 ctx->walking_bh--;
120
121 /* remove deleted bhs */
122 if (!ctx->walking_bh) {
123 qemu_mutex_lock(&ctx->bh_lock);
124 bhp = &ctx->first_bh;
125 while (*bhp) {
126 bh = *bhp;
127 if (bh->deleted && !bh->scheduled) {
128 *bhp = bh->next;
129 g_free(bh);
130 } else {
131 bhp = &bh->next;
132 }
133 }
134 qemu_mutex_unlock(&ctx->bh_lock);
135 }
136
137 return ret;
138 }
139
140 void qemu_bh_schedule_idle(QEMUBH *bh)
141 {
142 bh->idle = 1;
143 /* Make sure that idle & any writes needed by the callback are done
144 * before the locations are read in the aio_bh_poll.
145 */
146 atomic_mb_set(&bh->scheduled, 1);
147 }
148
149 void qemu_bh_schedule(QEMUBH *bh)
150 {
151 AioContext *ctx;
152
153 ctx = bh->ctx;
154 bh->idle = 0;
155 /* The memory barrier implicit in atomic_xchg makes sure that:
156 * 1. idle & any writes needed by the callback are done before the
157 * locations are read in the aio_bh_poll.
158 * 2. ctx is loaded before scheduled is set and the callback has a chance
159 * to execute.
160 */
161 if (atomic_xchg(&bh->scheduled, 1) == 0) {
162 aio_notify(ctx);
163 }
164 }
165
166
167 /* This func is async.
168 */
169 void qemu_bh_cancel(QEMUBH *bh)
170 {
171 bh->scheduled = 0;
172 }
173
174 /* This func is async.The bottom half will do the delete action at the finial
175 * end.
176 */
177 void qemu_bh_delete(QEMUBH *bh)
178 {
179 bh->scheduled = 0;
180 bh->deleted = 1;
181 }
182
183 int64_t
184 aio_compute_timeout(AioContext *ctx)
185 {
186 int64_t deadline;
187 int timeout = -1;
188 QEMUBH *bh;
189
190 for (bh = ctx->first_bh; bh; bh = bh->next) {
191 if (bh->scheduled) {
192 if (bh->idle) {
193 /* idle bottom halves will be polled at least
194 * every 10ms */
195 timeout = 10000000;
196 } else {
197 /* non-idle bottom halves will be executed
198 * immediately */
199 return 0;
200 }
201 }
202 }
203
204 deadline = timerlistgroup_deadline_ns(&ctx->tlg);
205 if (deadline == 0) {
206 return 0;
207 } else {
208 return qemu_soonest_timeout(timeout, deadline);
209 }
210 }
211
212 static gboolean
213 aio_ctx_prepare(GSource *source, gint *timeout)
214 {
215 AioContext *ctx = (AioContext *) source;
216
217 atomic_or(&ctx->notify_me, 1);
218
219 /* We assume there is no timeout already supplied */
220 *timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx));
221
222 if (aio_prepare(ctx)) {
223 *timeout = 0;
224 }
225
226 return *timeout == 0;
227 }
228
229 static gboolean
230 aio_ctx_check(GSource *source)
231 {
232 AioContext *ctx = (AioContext *) source;
233 QEMUBH *bh;
234
235 atomic_and(&ctx->notify_me, ~1);
236 aio_notify_accept(ctx);
237
238 for (bh = ctx->first_bh; bh; bh = bh->next) {
239 if (bh->scheduled) {
240 return true;
241 }
242 }
243 return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
244 }
245
246 static gboolean
247 aio_ctx_dispatch(GSource *source,
248 GSourceFunc callback,
249 gpointer user_data)
250 {
251 AioContext *ctx = (AioContext *) source;
252
253 assert(callback == NULL);
254 aio_dispatch(ctx);
255 return true;
256 }
257
258 static void
259 aio_ctx_finalize(GSource *source)
260 {
261 AioContext *ctx = (AioContext *) source;
262
263 thread_pool_free(ctx->thread_pool);
264
265 #ifdef CONFIG_LINUX_AIO
266 if (ctx->linux_aio) {
267 laio_detach_aio_context(ctx->linux_aio, ctx);
268 laio_cleanup(ctx->linux_aio);
269 ctx->linux_aio = NULL;
270 }
271 #endif
272
273 qemu_mutex_lock(&ctx->bh_lock);
274 while (ctx->first_bh) {
275 QEMUBH *next = ctx->first_bh->next;
276
277 /* qemu_bh_delete() must have been called on BHs in this AioContext */
278 assert(ctx->first_bh->deleted);
279
280 g_free(ctx->first_bh);
281 ctx->first_bh = next;
282 }
283 qemu_mutex_unlock(&ctx->bh_lock);
284
285 aio_set_event_notifier(ctx, &ctx->notifier, false, NULL);
286 event_notifier_cleanup(&ctx->notifier);
287 qemu_rec_mutex_destroy(&ctx->lock);
288 qemu_mutex_destroy(&ctx->bh_lock);
289 timerlistgroup_deinit(&ctx->tlg);
290 }
291
292 static GSourceFuncs aio_source_funcs = {
293 aio_ctx_prepare,
294 aio_ctx_check,
295 aio_ctx_dispatch,
296 aio_ctx_finalize
297 };
298
299 GSource *aio_get_g_source(AioContext *ctx)
300 {
301 g_source_ref(&ctx->source);
302 return &ctx->source;
303 }
304
305 ThreadPool *aio_get_thread_pool(AioContext *ctx)
306 {
307 if (!ctx->thread_pool) {
308 ctx->thread_pool = thread_pool_new(ctx);
309 }
310 return ctx->thread_pool;
311 }
312
313 #ifdef CONFIG_LINUX_AIO
314 LinuxAioState *aio_get_linux_aio(AioContext *ctx)
315 {
316 if (!ctx->linux_aio) {
317 ctx->linux_aio = laio_init();
318 laio_attach_aio_context(ctx->linux_aio, ctx);
319 }
320 return ctx->linux_aio;
321 }
322 #endif
323
324 void aio_notify(AioContext *ctx)
325 {
326 /* Write e.g. bh->scheduled before reading ctx->notify_me. Pairs
327 * with atomic_or in aio_ctx_prepare or atomic_add in aio_poll.
328 */
329 smp_mb();
330 if (ctx->notify_me) {
331 event_notifier_set(&ctx->notifier);
332 atomic_mb_set(&ctx->notified, true);
333 }
334 }
335
336 void aio_notify_accept(AioContext *ctx)
337 {
338 if (atomic_xchg(&ctx->notified, false)) {
339 event_notifier_test_and_clear(&ctx->notifier);
340 }
341 }
342
343 static void aio_timerlist_notify(void *opaque)
344 {
345 aio_notify(opaque);
346 }
347
348 static void event_notifier_dummy_cb(EventNotifier *e)
349 {
350 }
351
352 AioContext *aio_context_new(Error **errp)
353 {
354 int ret;
355 AioContext *ctx;
356
357 ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
358 aio_context_setup(ctx);
359
360 ret = event_notifier_init(&ctx->notifier, false);
361 if (ret < 0) {
362 error_setg_errno(errp, -ret, "Failed to initialize event notifier");
363 goto fail;
364 }
365 g_source_set_can_recurse(&ctx->source, true);
366 aio_set_event_notifier(ctx, &ctx->notifier,
367 false,
368 (EventNotifierHandler *)
369 event_notifier_dummy_cb);
370 #ifdef CONFIG_LINUX_AIO
371 ctx->linux_aio = NULL;
372 #endif
373 ctx->thread_pool = NULL;
374 qemu_mutex_init(&ctx->bh_lock);
375 qemu_rec_mutex_init(&ctx->lock);
376 timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
377
378 return ctx;
379 fail:
380 g_source_destroy(&ctx->source);
381 return NULL;
382 }
383
384 void aio_context_ref(AioContext *ctx)
385 {
386 g_source_ref(&ctx->source);
387 }
388
389 void aio_context_unref(AioContext *ctx)
390 {
391 g_source_unref(&ctx->source);
392 }
393
394 void aio_context_acquire(AioContext *ctx)
395 {
396 qemu_rec_mutex_lock(&ctx->lock);
397 }
398
399 void aio_context_release(AioContext *ctx)
400 {
401 qemu_rec_mutex_unlock(&ctx->lock);
402 }