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
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) */
44 QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
47 bh = g_new(QEMUBH, 1);
53 qemu_mutex_lock(&ctx->bh_lock);
54 bh->next = ctx->first_bh;
55 /* Make sure that the members are ready before putting bh into list */
58 qemu_mutex_unlock(&ctx->bh_lock);
62 /* Multiple occurrences of aio_bh_poll cannot be called concurrently */
63 int aio_bh_poll(AioContext *ctx)
65 QEMUBH *bh, **bhp, *next;
71 for (bh = ctx->first_bh; bh; bh = next) {
72 /* Make sure that fetching bh happens before accessing its members */
73 smp_read_barrier_depends();
75 /* The atomic_xchg is paired with the one in qemu_bh_schedule. The
76 * implicit memory barrier ensures that the callback sees all writes
77 * done by the scheduling thread. It also ensures that the scheduling
78 * thread sees the zero before bh->cb has run, and thus will call
79 * aio_notify again if necessary.
81 if (!bh->deleted && atomic_xchg(&bh->scheduled, 0)) {
91 /* remove deleted bhs */
92 if (!ctx->walking_bh) {
93 qemu_mutex_lock(&ctx->bh_lock);
104 qemu_mutex_unlock(&ctx->bh_lock);
110 void qemu_bh_schedule_idle(QEMUBH *bh)
113 /* Make sure that idle & any writes needed by the callback are done
114 * before the locations are read in the aio_bh_poll.
116 atomic_mb_set(&bh->scheduled, 1);
119 void qemu_bh_schedule(QEMUBH *bh)
125 /* The memory barrier implicit in atomic_xchg makes sure that:
126 * 1. idle & any writes needed by the callback are done before the
127 * locations are read in the aio_bh_poll.
128 * 2. ctx is loaded before scheduled is set and the callback has a chance
131 if (atomic_xchg(&bh->scheduled, 1) == 0) {
137 /* This func is async.
139 void qemu_bh_cancel(QEMUBH *bh)
144 /* This func is async.The bottom half will do the delete action at the finial
147 void qemu_bh_delete(QEMUBH *bh)
154 aio_compute_timeout(AioContext *ctx)
160 for (bh = ctx->first_bh; bh; bh = bh->next) {
161 if (!bh->deleted && bh->scheduled) {
163 /* idle bottom halves will be polled at least
167 /* non-idle bottom halves will be executed
174 deadline = timerlistgroup_deadline_ns(&ctx->tlg);
178 return qemu_soonest_timeout(timeout, deadline);
183 aio_ctx_prepare(GSource *source, gint *timeout)
185 AioContext *ctx = (AioContext *) source;
187 atomic_or(&ctx->notify_me, 1);
189 /* We assume there is no timeout already supplied */
190 *timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx));
192 if (aio_prepare(ctx)) {
196 return *timeout == 0;
200 aio_ctx_check(GSource *source)
202 AioContext *ctx = (AioContext *) source;
205 atomic_and(&ctx->notify_me, ~1);
206 aio_notify_accept(ctx);
208 for (bh = ctx->first_bh; bh; bh = bh->next) {
209 if (!bh->deleted && bh->scheduled) {
213 return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
217 aio_ctx_dispatch(GSource *source,
218 GSourceFunc callback,
221 AioContext *ctx = (AioContext *) source;
223 assert(callback == NULL);
229 aio_ctx_finalize(GSource *source)
231 AioContext *ctx = (AioContext *) source;
233 thread_pool_free(ctx->thread_pool);
235 qemu_mutex_lock(&ctx->bh_lock);
236 while (ctx->first_bh) {
237 QEMUBH *next = ctx->first_bh->next;
239 /* qemu_bh_delete() must have been called on BHs in this AioContext */
240 assert(ctx->first_bh->deleted);
242 g_free(ctx->first_bh);
243 ctx->first_bh = next;
245 qemu_mutex_unlock(&ctx->bh_lock);
247 aio_set_event_notifier(ctx, &ctx->notifier, NULL);
248 event_notifier_cleanup(&ctx->notifier);
249 rfifolock_destroy(&ctx->lock);
250 qemu_mutex_destroy(&ctx->bh_lock);
251 timerlistgroup_deinit(&ctx->tlg);
254 static GSourceFuncs aio_source_funcs = {
261 GSource *aio_get_g_source(AioContext *ctx)
263 g_source_ref(&ctx->source);
267 ThreadPool *aio_get_thread_pool(AioContext *ctx)
269 if (!ctx->thread_pool) {
270 ctx->thread_pool = thread_pool_new(ctx);
272 return ctx->thread_pool;
275 void aio_notify(AioContext *ctx)
277 /* Write e.g. bh->scheduled before reading ctx->notify_me. Pairs
278 * with atomic_or in aio_ctx_prepare or atomic_add in aio_poll.
281 if (ctx->notify_me) {
282 event_notifier_set(&ctx->notifier);
283 atomic_mb_set(&ctx->notified, true);
287 void aio_notify_accept(AioContext *ctx)
289 if (atomic_xchg(&ctx->notified, false)) {
290 event_notifier_test_and_clear(&ctx->notifier);
294 static void aio_timerlist_notify(void *opaque)
299 static void aio_rfifolock_cb(void *opaque)
301 /* Kick owner thread in case they are blocked in aio_poll() */
305 static void event_notifier_dummy_cb(EventNotifier *e)
309 AioContext *aio_context_new(Error **errp)
313 ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
314 ret = event_notifier_init(&ctx->notifier, false);
316 g_source_destroy(&ctx->source);
317 error_setg_errno(errp, -ret, "Failed to initialize event notifier");
320 g_source_set_can_recurse(&ctx->source, true);
321 aio_set_event_notifier(ctx, &ctx->notifier,
322 (EventNotifierHandler *)
323 event_notifier_dummy_cb);
324 ctx->thread_pool = NULL;
325 qemu_mutex_init(&ctx->bh_lock);
326 rfifolock_init(&ctx->lock, aio_rfifolock_cb, ctx);
327 timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
332 void aio_context_ref(AioContext *ctx)
334 g_source_ref(&ctx->source);
337 void aio_context_unref(AioContext *ctx)
339 g_source_unref(&ctx->source);
342 void aio_context_acquire(AioContext *ctx)
344 rfifolock_lock(&ctx->lock);
347 void aio_context_release(AioContext *ctx)
349 rfifolock_unlock(&ctx->lock);