ahci: unify sglist preparation
[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 #include "qemu/atomic.h"
30
31 /***********************************************************/
32 /* bottom halves (can be seen as timers which expire ASAP) */
33
34 struct QEMUBH {
35 AioContext *ctx;
36 QEMUBHFunc *cb;
37 void *opaque;
38 QEMUBH *next;
39 bool scheduled;
40 bool idle;
41 bool deleted;
42 };
43
44 QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
45 {
46 QEMUBH *bh;
47 bh = g_malloc0(sizeof(QEMUBH));
48 bh->ctx = ctx;
49 bh->cb = cb;
50 bh->opaque = opaque;
51 qemu_mutex_lock(&ctx->bh_lock);
52 bh->next = ctx->first_bh;
53 /* Make sure that the members are ready before putting bh into list */
54 smp_wmb();
55 ctx->first_bh = bh;
56 qemu_mutex_unlock(&ctx->bh_lock);
57 return bh;
58 }
59
60 /* Multiple occurrences of aio_bh_poll cannot be called concurrently */
61 int aio_bh_poll(AioContext *ctx)
62 {
63 QEMUBH *bh, **bhp, *next;
64 int ret;
65
66 ctx->walking_bh++;
67
68 ret = 0;
69 for (bh = ctx->first_bh; bh; bh = next) {
70 /* Make sure that fetching bh happens before accessing its members */
71 smp_read_barrier_depends();
72 next = bh->next;
73 if (!bh->deleted && bh->scheduled) {
74 bh->scheduled = 0;
75 /* Paired with write barrier in bh schedule to ensure reading for
76 * idle & callbacks coming after bh's scheduling.
77 */
78 smp_rmb();
79 if (!bh->idle)
80 ret = 1;
81 bh->idle = 0;
82 bh->cb(bh->opaque);
83 }
84 }
85
86 ctx->walking_bh--;
87
88 /* remove deleted bhs */
89 if (!ctx->walking_bh) {
90 qemu_mutex_lock(&ctx->bh_lock);
91 bhp = &ctx->first_bh;
92 while (*bhp) {
93 bh = *bhp;
94 if (bh->deleted) {
95 *bhp = bh->next;
96 g_free(bh);
97 } else {
98 bhp = &bh->next;
99 }
100 }
101 qemu_mutex_unlock(&ctx->bh_lock);
102 }
103
104 return ret;
105 }
106
107 void qemu_bh_schedule_idle(QEMUBH *bh)
108 {
109 if (bh->scheduled)
110 return;
111 bh->idle = 1;
112 /* Make sure that idle & any writes needed by the callback are done
113 * before the locations are read in the aio_bh_poll.
114 */
115 smp_wmb();
116 bh->scheduled = 1;
117 }
118
119 void qemu_bh_schedule(QEMUBH *bh)
120 {
121 AioContext *ctx;
122
123 if (bh->scheduled)
124 return;
125 ctx = bh->ctx;
126 bh->idle = 0;
127 /* Make sure that:
128 * 1. idle & any writes needed by the callback are done before the
129 * locations are read in the aio_bh_poll.
130 * 2. ctx is loaded before scheduled is set and the callback has a chance
131 * to execute.
132 */
133 smp_mb();
134 bh->scheduled = 1;
135 aio_notify(ctx);
136 }
137
138
139 /* This func is async.
140 */
141 void qemu_bh_cancel(QEMUBH *bh)
142 {
143 bh->scheduled = 0;
144 }
145
146 /* This func is async.The bottom half will do the delete action at the finial
147 * end.
148 */
149 void qemu_bh_delete(QEMUBH *bh)
150 {
151 bh->scheduled = 0;
152 bh->deleted = 1;
153 }
154
155 int64_t
156 aio_compute_timeout(AioContext *ctx)
157 {
158 int64_t deadline;
159 int timeout = -1;
160 QEMUBH *bh;
161
162 for (bh = ctx->first_bh; bh; bh = bh->next) {
163 if (!bh->deleted && bh->scheduled) {
164 if (bh->idle) {
165 /* idle bottom halves will be polled at least
166 * every 10ms */
167 timeout = 10000000;
168 } else {
169 /* non-idle bottom halves will be executed
170 * immediately */
171 return 0;
172 }
173 }
174 }
175
176 deadline = timerlistgroup_deadline_ns(&ctx->tlg);
177 if (deadline == 0) {
178 return 0;
179 } else {
180 return qemu_soonest_timeout(timeout, deadline);
181 }
182 }
183
184 static gboolean
185 aio_ctx_prepare(GSource *source, gint *timeout)
186 {
187 AioContext *ctx = (AioContext *) source;
188
189 /* We assume there is no timeout already supplied */
190 *timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx));
191
192 if (aio_prepare(ctx)) {
193 *timeout = 0;
194 }
195
196 return *timeout == 0;
197 }
198
199 static gboolean
200 aio_ctx_check(GSource *source)
201 {
202 AioContext *ctx = (AioContext *) source;
203 QEMUBH *bh;
204
205 for (bh = ctx->first_bh; bh; bh = bh->next) {
206 if (!bh->deleted && bh->scheduled) {
207 return true;
208 }
209 }
210 return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
211 }
212
213 static gboolean
214 aio_ctx_dispatch(GSource *source,
215 GSourceFunc callback,
216 gpointer user_data)
217 {
218 AioContext *ctx = (AioContext *) source;
219
220 assert(callback == NULL);
221 aio_dispatch(ctx);
222 return true;
223 }
224
225 static void
226 aio_ctx_finalize(GSource *source)
227 {
228 AioContext *ctx = (AioContext *) source;
229
230 thread_pool_free(ctx->thread_pool);
231 aio_set_event_notifier(ctx, &ctx->notifier, NULL);
232 event_notifier_cleanup(&ctx->notifier);
233 rfifolock_destroy(&ctx->lock);
234 qemu_mutex_destroy(&ctx->bh_lock);
235 g_array_free(ctx->pollfds, TRUE);
236 timerlistgroup_deinit(&ctx->tlg);
237 }
238
239 static GSourceFuncs aio_source_funcs = {
240 aio_ctx_prepare,
241 aio_ctx_check,
242 aio_ctx_dispatch,
243 aio_ctx_finalize
244 };
245
246 GSource *aio_get_g_source(AioContext *ctx)
247 {
248 g_source_ref(&ctx->source);
249 return &ctx->source;
250 }
251
252 ThreadPool *aio_get_thread_pool(AioContext *ctx)
253 {
254 if (!ctx->thread_pool) {
255 ctx->thread_pool = thread_pool_new(ctx);
256 }
257 return ctx->thread_pool;
258 }
259
260 void aio_set_dispatching(AioContext *ctx, bool dispatching)
261 {
262 ctx->dispatching = dispatching;
263 if (!dispatching) {
264 /* Write ctx->dispatching before reading e.g. bh->scheduled.
265 * Optimization: this is only needed when we're entering the "unsafe"
266 * phase where other threads must call event_notifier_set.
267 */
268 smp_mb();
269 }
270 }
271
272 void aio_notify(AioContext *ctx)
273 {
274 /* Write e.g. bh->scheduled before reading ctx->dispatching. */
275 smp_mb();
276 if (!ctx->dispatching) {
277 event_notifier_set(&ctx->notifier);
278 }
279 }
280
281 static void aio_timerlist_notify(void *opaque)
282 {
283 aio_notify(opaque);
284 }
285
286 static void aio_rfifolock_cb(void *opaque)
287 {
288 /* Kick owner thread in case they are blocked in aio_poll() */
289 aio_notify(opaque);
290 }
291
292 AioContext *aio_context_new(Error **errp)
293 {
294 int ret;
295 AioContext *ctx;
296 ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
297 ret = event_notifier_init(&ctx->notifier, false);
298 if (ret < 0) {
299 g_source_destroy(&ctx->source);
300 error_setg_errno(errp, -ret, "Failed to initialize event notifier");
301 return NULL;
302 }
303 aio_set_event_notifier(ctx, &ctx->notifier,
304 (EventNotifierHandler *)
305 event_notifier_test_and_clear);
306 ctx->pollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
307 ctx->thread_pool = NULL;
308 qemu_mutex_init(&ctx->bh_lock);
309 rfifolock_init(&ctx->lock, aio_rfifolock_cb, ctx);
310 timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
311
312 return ctx;
313 }
314
315 void aio_context_ref(AioContext *ctx)
316 {
317 g_source_ref(&ctx->source);
318 }
319
320 void aio_context_unref(AioContext *ctx)
321 {
322 g_source_unref(&ctx->source);
323 }
324
325 void aio_context_acquire(AioContext *ctx)
326 {
327 rfifolock_lock(&ctx->lock);
328 }
329
330 void aio_context_release(AioContext *ctx)
331 {
332 rfifolock_unlock(&ctx->lock);
333 }