Merge remote-tracking branch 'remotes/pmaydell/tags/pull-target-arm-20210330' into...
[qemu/ar7.git] / util / async.c
blob674dbefb7c2494887b3a7a1648908cb7209f0b4c
1 /*
2 * Data plane event loop
4 * Copyright (c) 2003-2008 Fabrice Bellard
5 * Copyright (c) 2009-2017 QEMU contributors
7 * Permission is hereby granted, free of charge, to any person obtaining a copy
8 * of this software and associated documentation files (the "Software"), to deal
9 * in the Software without restriction, including without limitation the rights
10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11 * copies of the Software, and to permit persons to whom the Software is
12 * furnished to do so, subject to the following conditions:
14 * The above copyright notice and this permission notice shall be included in
15 * all copies or substantial portions of the Software.
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
23 * THE SOFTWARE.
26 #include "qemu/osdep.h"
27 #include "qapi/error.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 "qemu/rcu_queue.h"
33 #include "block/raw-aio.h"
34 #include "qemu/coroutine_int.h"
35 #include "trace.h"
37 /***********************************************************/
38 /* bottom halves (can be seen as timers which expire ASAP) */
40 /* QEMUBH::flags values */
41 enum {
42 /* Already enqueued and waiting for aio_bh_poll() */
43 BH_PENDING = (1 << 0),
45 /* Invoke the callback */
46 BH_SCHEDULED = (1 << 1),
48 /* Delete without invoking callback */
49 BH_DELETED = (1 << 2),
51 /* Delete after invoking callback */
52 BH_ONESHOT = (1 << 3),
54 /* Schedule periodically when the event loop is idle */
55 BH_IDLE = (1 << 4),
58 struct QEMUBH {
59 AioContext *ctx;
60 QEMUBHFunc *cb;
61 void *opaque;
62 QSLIST_ENTRY(QEMUBH) next;
63 unsigned flags;
66 /* Called concurrently from any thread */
67 static void aio_bh_enqueue(QEMUBH *bh, unsigned new_flags)
69 AioContext *ctx = bh->ctx;
70 unsigned old_flags;
73 * The memory barrier implicit in qatomic_fetch_or makes sure that:
74 * 1. idle & any writes needed by the callback are done before the
75 * locations are read in the aio_bh_poll.
76 * 2. ctx is loaded before the callback has a chance to execute and bh
77 * could be freed.
79 old_flags = qatomic_fetch_or(&bh->flags, BH_PENDING | new_flags);
80 if (!(old_flags & BH_PENDING)) {
81 QSLIST_INSERT_HEAD_ATOMIC(&ctx->bh_list, bh, next);
84 aio_notify(ctx);
87 /* Only called from aio_bh_poll() and aio_ctx_finalize() */
88 static QEMUBH *aio_bh_dequeue(BHList *head, unsigned *flags)
90 QEMUBH *bh = QSLIST_FIRST_RCU(head);
92 if (!bh) {
93 return NULL;
96 QSLIST_REMOVE_HEAD(head, next);
99 * The qatomic_and is paired with aio_bh_enqueue(). The implicit memory
100 * barrier ensures that the callback sees all writes done by the scheduling
101 * thread. It also ensures that the scheduling thread sees the cleared
102 * flag before bh->cb has run, and thus will call aio_notify again if
103 * necessary.
105 *flags = qatomic_fetch_and(&bh->flags,
106 ~(BH_PENDING | BH_SCHEDULED | BH_IDLE));
107 return bh;
110 void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
112 QEMUBH *bh;
113 bh = g_new(QEMUBH, 1);
114 *bh = (QEMUBH){
115 .ctx = ctx,
116 .cb = cb,
117 .opaque = opaque,
119 aio_bh_enqueue(bh, BH_SCHEDULED | BH_ONESHOT);
122 QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
124 QEMUBH *bh;
125 bh = g_new(QEMUBH, 1);
126 *bh = (QEMUBH){
127 .ctx = ctx,
128 .cb = cb,
129 .opaque = opaque,
131 return bh;
134 void aio_bh_call(QEMUBH *bh)
136 bh->cb(bh->opaque);
139 /* Multiple occurrences of aio_bh_poll cannot be called concurrently. */
140 int aio_bh_poll(AioContext *ctx)
142 BHListSlice slice;
143 BHListSlice *s;
144 int ret = 0;
146 QSLIST_MOVE_ATOMIC(&slice.bh_list, &ctx->bh_list);
147 QSIMPLEQ_INSERT_TAIL(&ctx->bh_slice_list, &slice, next);
149 while ((s = QSIMPLEQ_FIRST(&ctx->bh_slice_list))) {
150 QEMUBH *bh;
151 unsigned flags;
153 bh = aio_bh_dequeue(&s->bh_list, &flags);
154 if (!bh) {
155 QSIMPLEQ_REMOVE_HEAD(&ctx->bh_slice_list, next);
156 continue;
159 if ((flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
160 /* Idle BHs don't count as progress */
161 if (!(flags & BH_IDLE)) {
162 ret = 1;
164 aio_bh_call(bh);
166 if (flags & (BH_DELETED | BH_ONESHOT)) {
167 g_free(bh);
171 return ret;
174 void qemu_bh_schedule_idle(QEMUBH *bh)
176 aio_bh_enqueue(bh, BH_SCHEDULED | BH_IDLE);
179 void qemu_bh_schedule(QEMUBH *bh)
181 aio_bh_enqueue(bh, BH_SCHEDULED);
184 /* This func is async.
186 void qemu_bh_cancel(QEMUBH *bh)
188 qatomic_and(&bh->flags, ~BH_SCHEDULED);
191 /* This func is async.The bottom half will do the delete action at the finial
192 * end.
194 void qemu_bh_delete(QEMUBH *bh)
196 aio_bh_enqueue(bh, BH_DELETED);
199 static int64_t aio_compute_bh_timeout(BHList *head, int timeout)
201 QEMUBH *bh;
203 QSLIST_FOREACH_RCU(bh, head, next) {
204 if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
205 if (bh->flags & BH_IDLE) {
206 /* idle bottom halves will be polled at least
207 * every 10ms */
208 timeout = 10000000;
209 } else {
210 /* non-idle bottom halves will be executed
211 * immediately */
212 return 0;
217 return timeout;
220 int64_t
221 aio_compute_timeout(AioContext *ctx)
223 BHListSlice *s;
224 int64_t deadline;
225 int timeout = -1;
227 timeout = aio_compute_bh_timeout(&ctx->bh_list, timeout);
228 if (timeout == 0) {
229 return 0;
232 QSIMPLEQ_FOREACH(s, &ctx->bh_slice_list, next) {
233 timeout = aio_compute_bh_timeout(&s->bh_list, timeout);
234 if (timeout == 0) {
235 return 0;
239 deadline = timerlistgroup_deadline_ns(&ctx->tlg);
240 if (deadline == 0) {
241 return 0;
242 } else {
243 return qemu_soonest_timeout(timeout, deadline);
247 static gboolean
248 aio_ctx_prepare(GSource *source, gint *timeout)
250 AioContext *ctx = (AioContext *) source;
252 qatomic_set(&ctx->notify_me, qatomic_read(&ctx->notify_me) | 1);
255 * Write ctx->notify_me before computing the timeout
256 * (reading bottom half flags, etc.). Pairs with
257 * smp_mb in aio_notify().
259 smp_mb();
261 /* We assume there is no timeout already supplied */
262 *timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx));
264 if (aio_prepare(ctx)) {
265 *timeout = 0;
268 return *timeout == 0;
271 static gboolean
272 aio_ctx_check(GSource *source)
274 AioContext *ctx = (AioContext *) source;
275 QEMUBH *bh;
276 BHListSlice *s;
278 /* Finish computing the timeout before clearing the flag. */
279 qatomic_store_release(&ctx->notify_me, qatomic_read(&ctx->notify_me) & ~1);
280 aio_notify_accept(ctx);
282 QSLIST_FOREACH_RCU(bh, &ctx->bh_list, next) {
283 if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
284 return true;
288 QSIMPLEQ_FOREACH(s, &ctx->bh_slice_list, next) {
289 QSLIST_FOREACH_RCU(bh, &s->bh_list, next) {
290 if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
291 return true;
295 return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
298 static gboolean
299 aio_ctx_dispatch(GSource *source,
300 GSourceFunc callback,
301 gpointer user_data)
303 AioContext *ctx = (AioContext *) source;
305 assert(callback == NULL);
306 aio_dispatch(ctx);
307 return true;
310 static void
311 aio_ctx_finalize(GSource *source)
313 AioContext *ctx = (AioContext *) source;
314 QEMUBH *bh;
315 unsigned flags;
317 thread_pool_free(ctx->thread_pool);
319 #ifdef CONFIG_LINUX_AIO
320 if (ctx->linux_aio) {
321 laio_detach_aio_context(ctx->linux_aio, ctx);
322 laio_cleanup(ctx->linux_aio);
323 ctx->linux_aio = NULL;
325 #endif
327 #ifdef CONFIG_LINUX_IO_URING
328 if (ctx->linux_io_uring) {
329 luring_detach_aio_context(ctx->linux_io_uring, ctx);
330 luring_cleanup(ctx->linux_io_uring);
331 ctx->linux_io_uring = NULL;
333 #endif
335 assert(QSLIST_EMPTY(&ctx->scheduled_coroutines));
336 qemu_bh_delete(ctx->co_schedule_bh);
338 /* There must be no aio_bh_poll() calls going on */
339 assert(QSIMPLEQ_EMPTY(&ctx->bh_slice_list));
341 while ((bh = aio_bh_dequeue(&ctx->bh_list, &flags))) {
342 /* qemu_bh_delete() must have been called on BHs in this AioContext */
343 assert(flags & BH_DELETED);
345 g_free(bh);
348 aio_set_event_notifier(ctx, &ctx->notifier, false, NULL, NULL);
349 event_notifier_cleanup(&ctx->notifier);
350 qemu_rec_mutex_destroy(&ctx->lock);
351 qemu_lockcnt_destroy(&ctx->list_lock);
352 timerlistgroup_deinit(&ctx->tlg);
353 aio_context_destroy(ctx);
356 static GSourceFuncs aio_source_funcs = {
357 aio_ctx_prepare,
358 aio_ctx_check,
359 aio_ctx_dispatch,
360 aio_ctx_finalize
363 GSource *aio_get_g_source(AioContext *ctx)
365 aio_context_use_g_source(ctx);
366 g_source_ref(&ctx->source);
367 return &ctx->source;
370 ThreadPool *aio_get_thread_pool(AioContext *ctx)
372 if (!ctx->thread_pool) {
373 ctx->thread_pool = thread_pool_new(ctx);
375 return ctx->thread_pool;
378 #ifdef CONFIG_LINUX_AIO
379 LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp)
381 if (!ctx->linux_aio) {
382 ctx->linux_aio = laio_init(errp);
383 if (ctx->linux_aio) {
384 laio_attach_aio_context(ctx->linux_aio, ctx);
387 return ctx->linux_aio;
390 LinuxAioState *aio_get_linux_aio(AioContext *ctx)
392 assert(ctx->linux_aio);
393 return ctx->linux_aio;
395 #endif
397 #ifdef CONFIG_LINUX_IO_URING
398 LuringState *aio_setup_linux_io_uring(AioContext *ctx, Error **errp)
400 if (ctx->linux_io_uring) {
401 return ctx->linux_io_uring;
404 ctx->linux_io_uring = luring_init(errp);
405 if (!ctx->linux_io_uring) {
406 return NULL;
409 luring_attach_aio_context(ctx->linux_io_uring, ctx);
410 return ctx->linux_io_uring;
413 LuringState *aio_get_linux_io_uring(AioContext *ctx)
415 assert(ctx->linux_io_uring);
416 return ctx->linux_io_uring;
418 #endif
420 void aio_notify(AioContext *ctx)
423 * Write e.g. bh->flags before writing ctx->notified. Pairs with smp_mb in
424 * aio_notify_accept.
426 smp_wmb();
427 qatomic_set(&ctx->notified, true);
430 * Write ctx->notified before reading ctx->notify_me. Pairs
431 * with smp_mb in aio_ctx_prepare or aio_poll.
433 smp_mb();
434 if (qatomic_read(&ctx->notify_me)) {
435 event_notifier_set(&ctx->notifier);
439 void aio_notify_accept(AioContext *ctx)
441 qatomic_set(&ctx->notified, false);
444 * Write ctx->notified before reading e.g. bh->flags. Pairs with smp_wmb
445 * in aio_notify.
447 smp_mb();
450 static void aio_timerlist_notify(void *opaque, QEMUClockType type)
452 aio_notify(opaque);
455 static void aio_context_notifier_cb(EventNotifier *e)
457 AioContext *ctx = container_of(e, AioContext, notifier);
459 event_notifier_test_and_clear(&ctx->notifier);
462 /* Returns true if aio_notify() was called (e.g. a BH was scheduled) */
463 static bool aio_context_notifier_poll(void *opaque)
465 EventNotifier *e = opaque;
466 AioContext *ctx = container_of(e, AioContext, notifier);
468 return qatomic_read(&ctx->notified);
471 static void co_schedule_bh_cb(void *opaque)
473 AioContext *ctx = opaque;
474 QSLIST_HEAD(, Coroutine) straight, reversed;
476 QSLIST_MOVE_ATOMIC(&reversed, &ctx->scheduled_coroutines);
477 QSLIST_INIT(&straight);
479 while (!QSLIST_EMPTY(&reversed)) {
480 Coroutine *co = QSLIST_FIRST(&reversed);
481 QSLIST_REMOVE_HEAD(&reversed, co_scheduled_next);
482 QSLIST_INSERT_HEAD(&straight, co, co_scheduled_next);
485 while (!QSLIST_EMPTY(&straight)) {
486 Coroutine *co = QSLIST_FIRST(&straight);
487 QSLIST_REMOVE_HEAD(&straight, co_scheduled_next);
488 trace_aio_co_schedule_bh_cb(ctx, co);
489 aio_context_acquire(ctx);
491 /* Protected by write barrier in qemu_aio_coroutine_enter */
492 qatomic_set(&co->scheduled, NULL);
493 qemu_aio_coroutine_enter(ctx, co);
494 aio_context_release(ctx);
498 AioContext *aio_context_new(Error **errp)
500 int ret;
501 AioContext *ctx;
503 ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
504 QSLIST_INIT(&ctx->bh_list);
505 QSIMPLEQ_INIT(&ctx->bh_slice_list);
506 aio_context_setup(ctx);
508 ret = event_notifier_init(&ctx->notifier, false);
509 if (ret < 0) {
510 error_setg_errno(errp, -ret, "Failed to initialize event notifier");
511 goto fail;
513 g_source_set_can_recurse(&ctx->source, true);
514 qemu_lockcnt_init(&ctx->list_lock);
516 ctx->co_schedule_bh = aio_bh_new(ctx, co_schedule_bh_cb, ctx);
517 QSLIST_INIT(&ctx->scheduled_coroutines);
519 aio_set_event_notifier(ctx, &ctx->notifier,
520 false,
521 aio_context_notifier_cb,
522 aio_context_notifier_poll);
523 #ifdef CONFIG_LINUX_AIO
524 ctx->linux_aio = NULL;
525 #endif
527 #ifdef CONFIG_LINUX_IO_URING
528 ctx->linux_io_uring = NULL;
529 #endif
531 ctx->thread_pool = NULL;
532 qemu_rec_mutex_init(&ctx->lock);
533 timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
535 ctx->poll_ns = 0;
536 ctx->poll_max_ns = 0;
537 ctx->poll_grow = 0;
538 ctx->poll_shrink = 0;
540 return ctx;
541 fail:
542 g_source_destroy(&ctx->source);
543 return NULL;
546 void aio_co_schedule(AioContext *ctx, Coroutine *co)
548 trace_aio_co_schedule(ctx, co);
549 const char *scheduled = qatomic_cmpxchg(&co->scheduled, NULL,
550 __func__);
552 if (scheduled) {
553 fprintf(stderr,
554 "%s: Co-routine was already scheduled in '%s'\n",
555 __func__, scheduled);
556 abort();
559 /* The coroutine might run and release the last ctx reference before we
560 * invoke qemu_bh_schedule(). Take a reference to keep ctx alive until
561 * we're done.
563 aio_context_ref(ctx);
565 QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines,
566 co, co_scheduled_next);
567 qemu_bh_schedule(ctx->co_schedule_bh);
569 aio_context_unref(ctx);
572 typedef struct AioCoRescheduleSelf {
573 Coroutine *co;
574 AioContext *new_ctx;
575 } AioCoRescheduleSelf;
577 static void aio_co_reschedule_self_bh(void *opaque)
579 AioCoRescheduleSelf *data = opaque;
580 aio_co_schedule(data->new_ctx, data->co);
583 void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx)
585 AioContext *old_ctx = qemu_get_current_aio_context();
587 if (old_ctx != new_ctx) {
588 AioCoRescheduleSelf data = {
589 .co = qemu_coroutine_self(),
590 .new_ctx = new_ctx,
593 * We can't directly schedule the coroutine in the target context
594 * because this would be racy: The other thread could try to enter the
595 * coroutine before it has yielded in this one.
597 aio_bh_schedule_oneshot(old_ctx, aio_co_reschedule_self_bh, &data);
598 qemu_coroutine_yield();
602 void aio_co_wake(struct Coroutine *co)
604 AioContext *ctx;
606 /* Read coroutine before co->ctx. Matches smp_wmb in
607 * qemu_coroutine_enter.
609 smp_read_barrier_depends();
610 ctx = qatomic_read(&co->ctx);
612 aio_co_enter(ctx, co);
615 void aio_co_enter(AioContext *ctx, struct Coroutine *co)
617 if (ctx != qemu_get_current_aio_context()) {
618 aio_co_schedule(ctx, co);
619 return;
622 if (qemu_in_coroutine()) {
623 Coroutine *self = qemu_coroutine_self();
624 assert(self != co);
625 QSIMPLEQ_INSERT_TAIL(&self->co_queue_wakeup, co, co_queue_next);
626 } else {
627 aio_context_acquire(ctx);
628 qemu_aio_coroutine_enter(ctx, co);
629 aio_context_release(ctx);
633 void aio_context_ref(AioContext *ctx)
635 g_source_ref(&ctx->source);
638 void aio_context_unref(AioContext *ctx)
640 g_source_unref(&ctx->source);
643 void aio_context_acquire(AioContext *ctx)
645 qemu_rec_mutex_lock(&ctx->lock);
648 void aio_context_release(AioContext *ctx)
650 qemu_rec_mutex_unlock(&ctx->lock);