Merge remote-tracking branch 'qemu/master'
[qemu/ar7.git] / async.c
blob0223d224ce6f23d187dc54ce92fc9573ef4d0d9c
1 /*
2 * QEMU System Emulator
4 * Copyright (c) 2003-2008 Fabrice Bellard
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:
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
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.
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"
31 /***********************************************************/
32 /* bottom halves (can be seen as timers which expire ASAP) */
34 struct QEMUBH {
35 AioContext *ctx;
36 QEMUBHFunc *cb;
37 void *opaque;
38 QEMUBH *next;
39 bool scheduled;
40 bool idle;
41 bool deleted;
44 QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
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;
60 /* Multiple occurrences of aio_bh_poll cannot be called concurrently */
61 int aio_bh_poll(AioContext *ctx)
63 QEMUBH *bh, **bhp, *next;
64 int ret;
66 ctx->walking_bh++;
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.
78 smp_rmb();
79 if (!bh->idle)
80 ret = 1;
81 bh->idle = 0;
82 bh->cb(bh->opaque);
86 ctx->walking_bh--;
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;
101 qemu_mutex_unlock(&ctx->bh_lock);
104 return ret;
107 void qemu_bh_schedule_idle(QEMUBH *bh)
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.
115 smp_wmb();
116 bh->scheduled = 1;
119 void qemu_bh_schedule(QEMUBH *bh)
121 AioContext *ctx;
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.
133 smp_mb();
134 bh->scheduled = 1;
135 aio_notify(ctx);
139 /* This func is async.
141 void qemu_bh_cancel(QEMUBH *bh)
143 bh->scheduled = 0;
146 /* This func is async.The bottom half will do the delete action at the finial
147 * end.
149 void qemu_bh_delete(QEMUBH *bh)
151 bh->scheduled = 0;
152 bh->deleted = 1;
155 static gboolean
156 aio_ctx_prepare(GSource *source, gint *timeout)
158 AioContext *ctx = (AioContext *) source;
159 QEMUBH *bh;
160 int deadline;
162 /* We assume there is no timeout already supplied */
163 *timeout = -1;
164 for (bh = ctx->first_bh; bh; bh = bh->next) {
165 if (!bh->deleted && bh->scheduled) {
166 if (bh->idle) {
167 /* idle bottom halves will be polled at least
168 * every 10ms */
169 *timeout = 10;
170 } else {
171 /* non-idle bottom halves will be executed
172 * immediately */
173 *timeout = 0;
174 return true;
179 deadline = qemu_timeout_ns_to_ms(timerlistgroup_deadline_ns(&ctx->tlg));
180 if (deadline == 0) {
181 *timeout = 0;
182 return true;
183 } else {
184 *timeout = qemu_soonest_timeout(*timeout, deadline);
187 return false;
190 static gboolean
191 aio_ctx_check(GSource *source)
193 AioContext *ctx = (AioContext *) source;
194 QEMUBH *bh;
196 for (bh = ctx->first_bh; bh; bh = bh->next) {
197 if (!bh->deleted && bh->scheduled) {
198 return true;
201 return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
204 static gboolean
205 aio_ctx_dispatch(GSource *source,
206 GSourceFunc callback,
207 gpointer user_data)
209 AioContext *ctx = (AioContext *) source;
211 assert(callback == NULL);
212 aio_poll(ctx, false);
213 return true;
216 static void
217 aio_ctx_finalize(GSource *source)
219 AioContext *ctx = (AioContext *) source;
221 thread_pool_free(ctx->thread_pool);
222 aio_set_event_notifier(ctx, &ctx->notifier, NULL);
223 event_notifier_cleanup(&ctx->notifier);
224 rfifolock_destroy(&ctx->lock);
225 qemu_mutex_destroy(&ctx->bh_lock);
226 g_array_free(ctx->pollfds, TRUE);
227 timerlistgroup_deinit(&ctx->tlg);
230 static GSourceFuncs aio_source_funcs = {
231 aio_ctx_prepare,
232 aio_ctx_check,
233 aio_ctx_dispatch,
234 aio_ctx_finalize
237 GSource *aio_get_g_source(AioContext *ctx)
239 g_source_ref(&ctx->source);
240 return &ctx->source;
243 ThreadPool *aio_get_thread_pool(AioContext *ctx)
245 if (!ctx->thread_pool) {
246 ctx->thread_pool = thread_pool_new(ctx);
248 return ctx->thread_pool;
251 void aio_set_dispatching(AioContext *ctx, bool dispatching)
253 ctx->dispatching = dispatching;
254 if (!dispatching) {
255 /* Write ctx->dispatching before reading e.g. bh->scheduled.
256 * Optimization: this is only needed when we're entering the "unsafe"
257 * phase where other threads must call event_notifier_set.
259 smp_mb();
263 void aio_notify(AioContext *ctx)
265 /* Write e.g. bh->scheduled before reading ctx->dispatching. */
266 smp_mb();
267 if (!ctx->dispatching) {
268 event_notifier_set(&ctx->notifier);
272 static void aio_timerlist_notify(void *opaque)
274 aio_notify(opaque);
277 static void aio_rfifolock_cb(void *opaque)
279 /* Kick owner thread in case they are blocked in aio_poll() */
280 aio_notify(opaque);
283 AioContext *aio_context_new(void)
285 AioContext *ctx;
286 ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
287 ctx->pollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
288 ctx->thread_pool = NULL;
289 qemu_mutex_init(&ctx->bh_lock);
290 rfifolock_init(&ctx->lock, aio_rfifolock_cb, ctx);
291 event_notifier_init(&ctx->notifier, false);
292 aio_set_event_notifier(ctx, &ctx->notifier,
293 (EventNotifierHandler *)
294 event_notifier_test_and_clear);
295 timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
297 return ctx;
300 void aio_context_ref(AioContext *ctx)
302 g_source_ref(&ctx->source);
305 void aio_context_unref(AioContext *ctx)
307 g_source_unref(&ctx->source);
310 void aio_context_acquire(AioContext *ctx)
312 rfifolock_lock(&ctx->lock);
315 void aio_context_release(AioContext *ctx)
317 rfifolock_unlock(&ctx->lock);