util/async.c

   1 /*
   2  * Data plane event loop
   3  *
   4  * Copyright (c) 2003-2008 Fabrice Bellard
   5  * Copyright (c) 2009-2017 QEMU contributors
   6  *
   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:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  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.
  24  */
  25
  26 #include "qemu/osdep.h"
  27 #include "qapi/error.h"
  28 #include "block/aio.h"
  29 #include "block/thread-pool.h"
  30 #include "block/graph-lock.h"
  31 #include "qemu/main-loop.h"
  32 #include "qemu/atomic.h"
  33 #include "qemu/rcu_queue.h"
  34 #include "block/raw-aio.h"
  35 #include "qemu/coroutine_int.h"
  36 #include "qemu/coroutine-tls.h"
  37 #include "sysemu/cpu-timers.h"
  38 #include "trace.h"
  39
  40 /***********************************************************/
  41 /* bottom halves (can be seen as timers which expire ASAP) */
  42
  43 /* QEMUBH::flags values */
  44 enum {
  45     /* Already enqueued and waiting for aio_bh_poll() */
  46     BH_PENDING   = (1 << 0),
  47
  48     /* Invoke the callback */
  49     BH_SCHEDULED = (1 << 1),
  50
  51     /* Delete without invoking callback */
  52     BH_DELETED   = (1 << 2),
  53
  54     /* Delete after invoking callback */
  55     BH_ONESHOT   = (1 << 3),
  56
  57     /* Schedule periodically when the event loop is idle */
  58     BH_IDLE      = (1 << 4),
  59 };
  60
  61 struct QEMUBH {
  62     AioContext *ctx;
  63     const char *name;
  64     QEMUBHFunc *cb;
  65     void *opaque;
  66     QSLIST_ENTRY(QEMUBH) next;
  67     unsigned flags;
  68 };
  69
  70 /* Called concurrently from any thread */
  71 static void aio_bh_enqueue(QEMUBH *bh, unsigned new_flags)
  72 {
  73     AioContext *ctx = bh->ctx;
  74     unsigned old_flags;
  75
  76     /*
  77      * The memory barrier implicit in qatomic_fetch_or makes sure that:
  78      * 1. idle & any writes needed by the callback are done before the
  79      *    locations are read in the aio_bh_poll.
  80      * 2. ctx is loaded before the callback has a chance to execute and bh
  81      *    could be freed.
  82      */
  83     old_flags = qatomic_fetch_or(&bh->flags, BH_PENDING | new_flags);
  84     if (!(old_flags & BH_PENDING)) {
  85         QSLIST_INSERT_HEAD_ATOMIC(&ctx->bh_list, bh, next);
  86     }
  87
  88     aio_notify(ctx);
  89     /*
  90      * Workaround for record/replay.
  91      * vCPU execution should be suspended when new BH is set.
  92      * This is needed to avoid guest timeouts caused
  93      * by the long cycles of the execution.
  94      */
  95     icount_notify_exit();
  96 }
  97
  98 /* Only called from aio_bh_poll() and aio_ctx_finalize() */
  99 static QEMUBH *aio_bh_dequeue(BHList *head, unsigned *flags)
 100 {
 101     QEMUBH *bh = QSLIST_FIRST_RCU(head);
 102
 103     if (!bh) {
 104         return NULL;
 105     }
 106
 107     QSLIST_REMOVE_HEAD(head, next);
 108
 109     /*
 110      * The qatomic_and is paired with aio_bh_enqueue().  The implicit memory
 111      * barrier ensures that the callback sees all writes done by the scheduling
 112      * thread.  It also ensures that the scheduling thread sees the cleared
 113      * flag before bh->cb has run, and thus will call aio_notify again if
 114      * necessary.
 115      */
 116     *flags = qatomic_fetch_and(&bh->flags,
 117                               ~(BH_PENDING | BH_SCHEDULED | BH_IDLE));
 118     return bh;
 119 }
 120
 121 void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb,
 122                                   void *opaque, const char *name)
 123 {
 124     QEMUBH *bh;
 125     bh = g_new(QEMUBH, 1);
 126     *bh = (QEMUBH){
 127         .ctx = ctx,
 128         .cb = cb,
 129         .opaque = opaque,
 130         .name = name,
 131     };
 132     aio_bh_enqueue(bh, BH_SCHEDULED | BH_ONESHOT);
 133 }
 134
 135 QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
 136                         const char *name)
 137 {
 138     QEMUBH *bh;
 139     bh = g_new(QEMUBH, 1);
 140     *bh = (QEMUBH){
 141         .ctx = ctx,
 142         .cb = cb,
 143         .opaque = opaque,
 144         .name = name,
 145     };
 146     return bh;
 147 }
 148
 149 void aio_bh_call(QEMUBH *bh)
 150 {
 151     bh->cb(bh->opaque);
 152 }
 153
 154 /* Multiple occurrences of aio_bh_poll cannot be called concurrently. */
 155 int aio_bh_poll(AioContext *ctx)
 156 {
 157     BHListSlice slice;
 158     BHListSlice *s;
 159     int ret = 0;
 160
 161     QSLIST_MOVE_ATOMIC(&slice.bh_list, &ctx->bh_list);
 162     QSIMPLEQ_INSERT_TAIL(&ctx->bh_slice_list, &slice, next);
 163
 164     while ((s = QSIMPLEQ_FIRST(&ctx->bh_slice_list))) {
 165         QEMUBH *bh;
 166         unsigned flags;
 167
 168         bh = aio_bh_dequeue(&s->bh_list, &flags);
 169         if (!bh) {
 170             QSIMPLEQ_REMOVE_HEAD(&ctx->bh_slice_list, next);
 171             continue;
 172         }
 173
 174         if ((flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
 175             /* Idle BHs don't count as progress */
 176             if (!(flags & BH_IDLE)) {
 177                 ret = 1;
 178             }
 179             aio_bh_call(bh);
 180         }
 181         if (flags & (BH_DELETED | BH_ONESHOT)) {
 182             g_free(bh);
 183         }
 184     }
 185
 186     return ret;
 187 }
 188
 189 void qemu_bh_schedule_idle(QEMUBH *bh)
 190 {
 191     aio_bh_enqueue(bh, BH_SCHEDULED | BH_IDLE);
 192 }
 193
 194 void qemu_bh_schedule(QEMUBH *bh)
 195 {
 196     aio_bh_enqueue(bh, BH_SCHEDULED);
 197 }
 198
 199 /* This func is async.
 200  */
 201 void qemu_bh_cancel(QEMUBH *bh)
 202 {
 203     qatomic_and(&bh->flags, ~BH_SCHEDULED);
 204 }
 205
 206 /* This func is async.The bottom half will do the delete action at the finial
 207  * end.
 208  */
 209 void qemu_bh_delete(QEMUBH *bh)
 210 {
 211     aio_bh_enqueue(bh, BH_DELETED);
 212 }
 213
 214 static int64_t aio_compute_bh_timeout(BHList *head, int timeout)
 215 {
 216     QEMUBH *bh;
 217
 218     QSLIST_FOREACH_RCU(bh, head, next) {
 219         if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
 220             if (bh->flags & BH_IDLE) {
 221                 /* idle bottom halves will be polled at least
 222                  * every 10ms */
 223                 timeout = 10000000;
 224             } else {
 225                 /* non-idle bottom halves will be executed
 226                  * immediately */
 227                 return 0;
 228             }
 229         }
 230     }
 231
 232     return timeout;
 233 }
 234
 235 int64_t
 236 aio_compute_timeout(AioContext *ctx)
 237 {
 238     BHListSlice *s;
 239     int64_t deadline;
 240     int timeout = -1;
 241
 242     timeout = aio_compute_bh_timeout(&ctx->bh_list, timeout);
 243     if (timeout == 0) {
 244         return 0;
 245     }
 246
 247     QSIMPLEQ_FOREACH(s, &ctx->bh_slice_list, next) {
 248         timeout = aio_compute_bh_timeout(&s->bh_list, timeout);
 249         if (timeout == 0) {
 250             return 0;
 251         }
 252     }
 253
 254     deadline = timerlistgroup_deadline_ns(&ctx->tlg);
 255     if (deadline == 0) {
 256         return 0;
 257     } else {
 258         return qemu_soonest_timeout(timeout, deadline);
 259     }
 260 }
 261
 262 static gboolean
 263 aio_ctx_prepare(GSource *source, gint    *timeout)
 264 {
 265     AioContext *ctx = (AioContext *) source;
 266
 267     qatomic_set(&ctx->notify_me, qatomic_read(&ctx->notify_me) | 1);
 268
 269     /*
 270      * Write ctx->notify_me before computing the timeout
 271      * (reading bottom half flags, etc.).  Pairs with
 272      * smp_mb in aio_notify().
 273      */
 274     smp_mb();
 275
 276     /* We assume there is no timeout already supplied */
 277     *timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx));
 278
 279     if (aio_prepare(ctx)) {
 280         *timeout = 0;
 281     }
 282
 283     return *timeout == 0;
 284 }
 285
 286 static gboolean
 287 aio_ctx_check(GSource *source)
 288 {
 289     AioContext *ctx = (AioContext *) source;
 290     QEMUBH *bh;
 291     BHListSlice *s;
 292
 293     /* Finish computing the timeout before clearing the flag.  */
 294     qatomic_store_release(&ctx->notify_me, qatomic_read(&ctx->notify_me) & ~1);
 295     aio_notify_accept(ctx);
 296
 297     QSLIST_FOREACH_RCU(bh, &ctx->bh_list, next) {
 298         if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
 299             return true;
 300         }
 301     }
 302
 303     QSIMPLEQ_FOREACH(s, &ctx->bh_slice_list, next) {
 304         QSLIST_FOREACH_RCU(bh, &s->bh_list, next) {
 305             if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
 306                 return true;
 307             }
 308         }
 309     }
 310     return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
 311 }
 312
 313 static gboolean
 314 aio_ctx_dispatch(GSource     *source,
 315                  GSourceFunc  callback,
 316                  gpointer     user_data)
 317 {
 318     AioContext *ctx = (AioContext *) source;
 319
 320     assert(callback == NULL);
 321     aio_dispatch(ctx);
 322     return true;
 323 }
 324
 325 static void
 326 aio_ctx_finalize(GSource     *source)
 327 {
 328     AioContext *ctx = (AioContext *) source;
 329     QEMUBH *bh;
 330     unsigned flags;
 331
 332     thread_pool_free(ctx->thread_pool);
 333
 334 #ifdef CONFIG_LINUX_AIO
 335     if (ctx->linux_aio) {
 336         laio_detach_aio_context(ctx->linux_aio, ctx);
 337         laio_cleanup(ctx->linux_aio);
 338         ctx->linux_aio = NULL;
 339     }
 340 #endif
 341
 342 #ifdef CONFIG_LINUX_IO_URING
 343     if (ctx->linux_io_uring) {
 344         luring_detach_aio_context(ctx->linux_io_uring, ctx);
 345         luring_cleanup(ctx->linux_io_uring);
 346         ctx->linux_io_uring = NULL;
 347     }
 348 #endif
 349
 350     assert(QSLIST_EMPTY(&ctx->scheduled_coroutines));
 351     qemu_bh_delete(ctx->co_schedule_bh);
 352
 353     /* There must be no aio_bh_poll() calls going on */
 354     assert(QSIMPLEQ_EMPTY(&ctx->bh_slice_list));
 355
 356     while ((bh = aio_bh_dequeue(&ctx->bh_list, &flags))) {
 357         /*
 358          * qemu_bh_delete() must have been called on BHs in this AioContext. In
 359          * many cases memory leaks, hangs, or inconsistent state occur when a
 360          * BH is leaked because something still expects it to run.
 361          *
 362          * If you hit this, fix the lifecycle of the BH so that
 363          * qemu_bh_delete() and any associated cleanup is called before the
 364          * AioContext is finalized.
 365          */
 366         if (unlikely(!(flags & BH_DELETED))) {
 367             fprintf(stderr, "%s: BH '%s' leaked, aborting...\n",
 368                     __func__, bh->name);
 369             abort();
 370         }
 371
 372         g_free(bh);
 373     }
 374
 375     aio_set_event_notifier(ctx, &ctx->notifier, false, NULL, NULL, NULL);
 376     event_notifier_cleanup(&ctx->notifier);
 377     qemu_rec_mutex_destroy(&ctx->lock);
 378     qemu_lockcnt_destroy(&ctx->list_lock);
 379     timerlistgroup_deinit(&ctx->tlg);
 380     unregister_aiocontext(ctx);
 381     aio_context_destroy(ctx);
 382 }
 383
 384 static GSourceFuncs aio_source_funcs = {
 385     aio_ctx_prepare,
 386     aio_ctx_check,
 387     aio_ctx_dispatch,
 388     aio_ctx_finalize
 389 };
 390
 391 GSource *aio_get_g_source(AioContext *ctx)
 392 {
 393     aio_context_use_g_source(ctx);
 394     g_source_ref(&ctx->source);
 395     return &ctx->source;
 396 }
 397
 398 ThreadPool *aio_get_thread_pool(AioContext *ctx)
 399 {
 400     if (!ctx->thread_pool) {
 401         ctx->thread_pool = thread_pool_new(ctx);
 402     }
 403     return ctx->thread_pool;
 404 }
 405
 406 #ifdef CONFIG_LINUX_AIO
 407 LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp)
 408 {
 409     if (!ctx->linux_aio) {
 410         ctx->linux_aio = laio_init(errp);
 411         if (ctx->linux_aio) {
 412             laio_attach_aio_context(ctx->linux_aio, ctx);
 413         }
 414     }
 415     return ctx->linux_aio;
 416 }
 417
 418 LinuxAioState *aio_get_linux_aio(AioContext *ctx)
 419 {
 420     assert(ctx->linux_aio);
 421     return ctx->linux_aio;
 422 }
 423 #endif
 424
 425 #ifdef CONFIG_LINUX_IO_URING
 426 LuringState *aio_setup_linux_io_uring(AioContext *ctx, Error **errp)
 427 {
 428     if (ctx->linux_io_uring) {
 429         return ctx->linux_io_uring;
 430     }
 431
 432     ctx->linux_io_uring = luring_init(errp);
 433     if (!ctx->linux_io_uring) {
 434         return NULL;
 435     }
 436
 437     luring_attach_aio_context(ctx->linux_io_uring, ctx);
 438     return ctx->linux_io_uring;
 439 }
 440
 441 LuringState *aio_get_linux_io_uring(AioContext *ctx)
 442 {
 443     assert(ctx->linux_io_uring);
 444     return ctx->linux_io_uring;
 445 }
 446 #endif
 447
 448 void aio_notify(AioContext *ctx)
 449 {
 450     /*
 451      * Write e.g. bh->flags before writing ctx->notified.  Pairs with smp_mb in
 452      * aio_notify_accept.
 453      */
 454     smp_wmb();
 455     qatomic_set(&ctx->notified, true);
 456
 457     /*
 458      * Write ctx->notified before reading ctx->notify_me.  Pairs
 459      * with smp_mb in aio_ctx_prepare or aio_poll.
 460      */
 461     smp_mb();
 462     if (qatomic_read(&ctx->notify_me)) {
 463         event_notifier_set(&ctx->notifier);
 464     }
 465 }
 466
 467 void aio_notify_accept(AioContext *ctx)
 468 {
 469     qatomic_set(&ctx->notified, false);
 470
 471     /*
 472      * Write ctx->notified before reading e.g. bh->flags.  Pairs with smp_wmb
 473      * in aio_notify.
 474      */
 475     smp_mb();
 476 }
 477
 478 static void aio_timerlist_notify(void *opaque, QEMUClockType type)
 479 {
 480     aio_notify(opaque);
 481 }
 482
 483 static void aio_context_notifier_cb(EventNotifier *e)
 484 {
 485     AioContext *ctx = container_of(e, AioContext, notifier);
 486
 487     event_notifier_test_and_clear(&ctx->notifier);
 488 }
 489
 490 /* Returns true if aio_notify() was called (e.g. a BH was scheduled) */
 491 static bool aio_context_notifier_poll(void *opaque)
 492 {
 493     EventNotifier *e = opaque;
 494     AioContext *ctx = container_of(e, AioContext, notifier);
 495
 496     return qatomic_read(&ctx->notified);
 497 }
 498
 499 static void aio_context_notifier_poll_ready(EventNotifier *e)
 500 {
 501     /* Do nothing, we just wanted to kick the event loop */
 502 }
 503
 504 static void co_schedule_bh_cb(void *opaque)
 505 {
 506     AioContext *ctx = opaque;
 507     QSLIST_HEAD(, Coroutine) straight, reversed;
 508
 509     QSLIST_MOVE_ATOMIC(&reversed, &ctx->scheduled_coroutines);
 510     QSLIST_INIT(&straight);
 511
 512     while (!QSLIST_EMPTY(&reversed)) {
 513         Coroutine *co = QSLIST_FIRST(&reversed);
 514         QSLIST_REMOVE_HEAD(&reversed, co_scheduled_next);
 515         QSLIST_INSERT_HEAD(&straight, co, co_scheduled_next);
 516     }
 517
 518     while (!QSLIST_EMPTY(&straight)) {
 519         Coroutine *co = QSLIST_FIRST(&straight);
 520         QSLIST_REMOVE_HEAD(&straight, co_scheduled_next);
 521         trace_aio_co_schedule_bh_cb(ctx, co);
 522         aio_context_acquire(ctx);
 523
 524         /* Protected by write barrier in qemu_aio_coroutine_enter */
 525         qatomic_set(&co->scheduled, NULL);
 526         qemu_aio_coroutine_enter(ctx, co);
 527         aio_context_release(ctx);
 528     }
 529 }
 530
 531 AioContext *aio_context_new(Error **errp)
 532 {
 533     int ret;
 534     AioContext *ctx;
 535
 536     ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
 537     QSLIST_INIT(&ctx->bh_list);
 538     QSIMPLEQ_INIT(&ctx->bh_slice_list);
 539     aio_context_setup(ctx);
 540
 541     ret = event_notifier_init(&ctx->notifier, false);
 542     if (ret < 0) {
 543         error_setg_errno(errp, -ret, "Failed to initialize event notifier");
 544         goto fail;
 545     }
 546     g_source_set_can_recurse(&ctx->source, true);
 547     qemu_lockcnt_init(&ctx->list_lock);
 548
 549     ctx->co_schedule_bh = aio_bh_new(ctx, co_schedule_bh_cb, ctx);
 550     QSLIST_INIT(&ctx->scheduled_coroutines);
 551
 552     aio_set_event_notifier(ctx, &ctx->notifier,
 553                            false,
 554                            aio_context_notifier_cb,
 555                            aio_context_notifier_poll,
 556                            aio_context_notifier_poll_ready);
 557 #ifdef CONFIG_LINUX_AIO
 558     ctx->linux_aio = NULL;
 559 #endif
 560
 561 #ifdef CONFIG_LINUX_IO_URING
 562     ctx->linux_io_uring = NULL;
 563 #endif
 564
 565     ctx->thread_pool = NULL;
 566     qemu_rec_mutex_init(&ctx->lock);
 567     timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
 568
 569     ctx->poll_ns = 0;
 570     ctx->poll_max_ns = 0;
 571     ctx->poll_grow = 0;
 572     ctx->poll_shrink = 0;
 573
 574     ctx->aio_max_batch = 0;
 575
 576     ctx->thread_pool_min = 0;
 577     ctx->thread_pool_max = THREAD_POOL_MAX_THREADS_DEFAULT;
 578
 579     register_aiocontext(ctx);
 580
 581     return ctx;
 582 fail:
 583     g_source_destroy(&ctx->source);
 584     return NULL;
 585 }
 586
 587 void aio_co_schedule(AioContext *ctx, Coroutine *co)
 588 {
 589     trace_aio_co_schedule(ctx, co);
 590     const char *scheduled = qatomic_cmpxchg(&co->scheduled, NULL,
 591                                            __func__);
 592
 593     if (scheduled) {
 594         fprintf(stderr,
 595                 "%s: Co-routine was already scheduled in '%s'\n",
 596                 __func__, scheduled);
 597         abort();
 598     }
 599
 600     /* The coroutine might run and release the last ctx reference before we
 601      * invoke qemu_bh_schedule().  Take a reference to keep ctx alive until
 602      * we're done.
 603      */
 604     aio_context_ref(ctx);
 605
 606     QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines,
 607                               co, co_scheduled_next);
 608     qemu_bh_schedule(ctx->co_schedule_bh);
 609
 610     aio_context_unref(ctx);
 611 }
 612
 613 typedef struct AioCoRescheduleSelf {
 614     Coroutine *co;
 615     AioContext *new_ctx;
 616 } AioCoRescheduleSelf;
 617
 618 static void aio_co_reschedule_self_bh(void *opaque)
 619 {
 620     AioCoRescheduleSelf *data = opaque;
 621     aio_co_schedule(data->new_ctx, data->co);
 622 }
 623
 624 void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx)
 625 {
 626     AioContext *old_ctx = qemu_get_current_aio_context();
 627
 628     if (old_ctx != new_ctx) {
 629         AioCoRescheduleSelf data = {
 630             .co = qemu_coroutine_self(),
 631             .new_ctx = new_ctx,
 632         };
 633         /*
 634          * We can't directly schedule the coroutine in the target context
 635          * because this would be racy: The other thread could try to enter the
 636          * coroutine before it has yielded in this one.
 637          */
 638         aio_bh_schedule_oneshot(old_ctx, aio_co_reschedule_self_bh, &data);
 639         qemu_coroutine_yield();
 640     }
 641 }
 642
 643 void aio_co_wake(Coroutine *co)
 644 {
 645     AioContext *ctx;
 646
 647     /* Read coroutine before co->ctx.  Matches smp_wmb in
 648      * qemu_coroutine_enter.
 649      */
 650     smp_read_barrier_depends();
 651     ctx = qatomic_read(&co->ctx);
 652
 653     aio_co_enter(ctx, co);
 654 }
 655
 656 void aio_co_enter(AioContext *ctx, Coroutine *co)
 657 {
 658     if (ctx != qemu_get_current_aio_context()) {
 659         aio_co_schedule(ctx, co);
 660         return;
 661     }
 662
 663     if (qemu_in_coroutine()) {
 664         Coroutine *self = qemu_coroutine_self();
 665         assert(self != co);
 666         QSIMPLEQ_INSERT_TAIL(&self->co_queue_wakeup, co, co_queue_next);
 667     } else {
 668         aio_context_acquire(ctx);
 669         qemu_aio_coroutine_enter(ctx, co);
 670         aio_context_release(ctx);
 671     }
 672 }
 673
 674 void aio_context_ref(AioContext *ctx)
 675 {
 676     g_source_ref(&ctx->source);
 677 }
 678
 679 void aio_context_unref(AioContext *ctx)
 680 {
 681     g_source_unref(&ctx->source);
 682 }
 683
 684 void aio_context_acquire(AioContext *ctx)
 685 {
 686     qemu_rec_mutex_lock(&ctx->lock);
 687 }
 688
 689 void aio_context_release(AioContext *ctx)
 690 {
 691     qemu_rec_mutex_unlock(&ctx->lock);
 692 }
 693
 694 QEMU_DEFINE_STATIC_CO_TLS(AioContext *, my_aiocontext)
 695
 696 AioContext *qemu_get_current_aio_context(void)
 697 {
 698     AioContext *ctx = get_my_aiocontext();
 699     if (ctx) {
 700         return ctx;
 701     }
 702     if (qemu_mutex_iothread_locked()) {
 703         /* Possibly in a vCPU thread.  */
 704         return qemu_get_aio_context();
 705     }
 706     return NULL;
 707 }
 708
 709 void qemu_set_current_aio_context(AioContext *ctx)
 710 {
 711     assert(!get_my_aiocontext());
 712     set_my_aiocontext(ctx);
 713 }
 714
 715 void aio_context_set_thread_pool_params(AioContext *ctx, int64_t min,
 716                                         int64_t max, Error **errp)
 717 {
 718
 719     if (min > max || !max || min > INT_MAX || max > INT_MAX) {
 720         error_setg(errp, "bad thread-pool-min/thread-pool-max values");
 721         return;
 722     }
 723
 724     ctx->thread_pool_min = min;
 725     ctx->thread_pool_max = max;
 726
 727     if (ctx->thread_pool) {
 728         thread_pool_update_params(ctx->thread_pool, ctx);
 729     }
 730 }