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     MemReentrancyGuard *reentrancy_guard;
  69 };
  70
  71 /* Called concurrently from any thread */
  72 static void aio_bh_enqueue(QEMUBH *bh, unsigned new_flags)
  73 {
  74     AioContext *ctx = bh->ctx;
  75     unsigned old_flags;
  76
  77     /*
  78      * Synchronizes with atomic_fetch_and() in aio_bh_dequeue(), ensuring that
  79      * insertion starts after BH_PENDING is set.
  80      */
  81     old_flags = qatomic_fetch_or(&bh->flags, BH_PENDING | new_flags);
  82
  83     if (!(old_flags & BH_PENDING)) {
  84         /*
  85          * At this point the bottom half becomes visible to aio_bh_poll().
  86          * This insertion thus synchronizes with QSLIST_MOVE_ATOMIC in
  87          * aio_bh_poll(), ensuring that:
  88          * 1. any writes needed by the callback are visible from the callback
  89          *    after aio_bh_dequeue() returns bh.
  90          * 2. ctx is loaded before the callback has a chance to execute and bh
  91          *    could be freed.
  92          */
  93         QSLIST_INSERT_HEAD_ATOMIC(&ctx->bh_list, bh, next);
  94     }
  95
  96     aio_notify(ctx);
  97     if (unlikely(icount_enabled())) {
  98         /*
  99          * Workaround for record/replay.
 100          * vCPU execution should be suspended when new BH is set.
 101          * This is needed to avoid guest timeouts caused
 102          * by the long cycles of the execution.
 103          */
 104         icount_notify_exit();
 105     }
 106 }
 107
 108 /* Only called from aio_bh_poll() and aio_ctx_finalize() */
 109 static QEMUBH *aio_bh_dequeue(BHList *head, unsigned *flags)
 110 {
 111     QEMUBH *bh = QSLIST_FIRST_RCU(head);
 112
 113     if (!bh) {
 114         return NULL;
 115     }
 116
 117     QSLIST_REMOVE_HEAD(head, next);
 118
 119     /*
 120      * Synchronizes with qatomic_fetch_or() in aio_bh_enqueue(), ensuring that
 121      * the removal finishes before BH_PENDING is reset.
 122      */
 123     *flags = qatomic_fetch_and(&bh->flags,
 124                               ~(BH_PENDING | BH_SCHEDULED | BH_IDLE));
 125     return bh;
 126 }
 127
 128 void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb,
 129                                   void *opaque, const char *name)
 130 {
 131     QEMUBH *bh;
 132     bh = g_new(QEMUBH, 1);
 133     *bh = (QEMUBH){
 134         .ctx = ctx,
 135         .cb = cb,
 136         .opaque = opaque,
 137         .name = name,
 138     };
 139     aio_bh_enqueue(bh, BH_SCHEDULED | BH_ONESHOT);
 140 }
 141
 142 QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
 143                         const char *name, MemReentrancyGuard *reentrancy_guard)
 144 {
 145     QEMUBH *bh;
 146     bh = g_new(QEMUBH, 1);
 147     *bh = (QEMUBH){
 148         .ctx = ctx,
 149         .cb = cb,
 150         .opaque = opaque,
 151         .name = name,
 152         .reentrancy_guard = reentrancy_guard,
 153     };
 154     return bh;
 155 }
 156
 157 void aio_bh_call(QEMUBH *bh)
 158 {
 159     bool last_engaged_in_io = false;
 160
 161     /* Make a copy of the guard-pointer as cb may free the bh */
 162     MemReentrancyGuard *reentrancy_guard = bh->reentrancy_guard;
 163     if (reentrancy_guard) {
 164         last_engaged_in_io = reentrancy_guard->engaged_in_io;
 165         if (reentrancy_guard->engaged_in_io) {
 166             trace_reentrant_aio(bh->ctx, bh->name);
 167         }
 168         reentrancy_guard->engaged_in_io = true;
 169     }
 170
 171     bh->cb(bh->opaque);
 172
 173     if (reentrancy_guard) {
 174         reentrancy_guard->engaged_in_io = last_engaged_in_io;
 175     }
 176 }
 177
 178 /* Multiple occurrences of aio_bh_poll cannot be called concurrently. */
 179 int aio_bh_poll(AioContext *ctx)
 180 {
 181     BHListSlice slice;
 182     BHListSlice *s;
 183     int ret = 0;
 184
 185     /* Synchronizes with QSLIST_INSERT_HEAD_ATOMIC in aio_bh_enqueue().  */
 186     QSLIST_MOVE_ATOMIC(&slice.bh_list, &ctx->bh_list);
 187
 188     /*
 189      * GCC13 [-Werror=dangling-pointer=] complains that the local variable
 190      * 'slice' is being stored in the global 'ctx->bh_slice_list' but the
 191      * list is emptied before this function returns.
 192      */
 193 #if !defined(__clang__)
 194 #pragma GCC diagnostic push
 195 #pragma GCC diagnostic ignored "-Wpragmas"
 196 #pragma GCC diagnostic ignored "-Wdangling-pointer="
 197 #endif
 198     QSIMPLEQ_INSERT_TAIL(&ctx->bh_slice_list, &slice, next);
 199 #if !defined(__clang__)
 200 #pragma GCC diagnostic pop
 201 #endif
 202
 203     while ((s = QSIMPLEQ_FIRST(&ctx->bh_slice_list))) {
 204         QEMUBH *bh;
 205         unsigned flags;
 206
 207         bh = aio_bh_dequeue(&s->bh_list, &flags);
 208         if (!bh) {
 209             QSIMPLEQ_REMOVE_HEAD(&ctx->bh_slice_list, next);
 210             continue;
 211         }
 212
 213         if ((flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
 214             /* Idle BHs don't count as progress */
 215             if (!(flags & BH_IDLE)) {
 216                 ret = 1;
 217             }
 218             aio_bh_call(bh);
 219         }
 220         if (flags & (BH_DELETED | BH_ONESHOT)) {
 221             g_free(bh);
 222         }
 223     }
 224
 225     return ret;
 226 }
 227
 228 void qemu_bh_schedule_idle(QEMUBH *bh)
 229 {
 230     aio_bh_enqueue(bh, BH_SCHEDULED | BH_IDLE);
 231 }
 232
 233 void qemu_bh_schedule(QEMUBH *bh)
 234 {
 235     aio_bh_enqueue(bh, BH_SCHEDULED);
 236 }
 237
 238 /* This func is async.
 239  */
 240 void qemu_bh_cancel(QEMUBH *bh)
 241 {
 242     qatomic_and(&bh->flags, ~BH_SCHEDULED);
 243 }
 244
 245 /* This func is async.The bottom half will do the delete action at the finial
 246  * end.
 247  */
 248 void qemu_bh_delete(QEMUBH *bh)
 249 {
 250     aio_bh_enqueue(bh, BH_DELETED);
 251 }
 252
 253 static int64_t aio_compute_bh_timeout(BHList *head, int timeout)
 254 {
 255     QEMUBH *bh;
 256
 257     QSLIST_FOREACH_RCU(bh, head, next) {
 258         if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
 259             if (bh->flags & BH_IDLE) {
 260                 /* idle bottom halves will be polled at least
 261                  * every 10ms */
 262                 timeout = 10000000;
 263             } else {
 264                 /* non-idle bottom halves will be executed
 265                  * immediately */
 266                 return 0;
 267             }
 268         }
 269     }
 270
 271     return timeout;
 272 }
 273
 274 int64_t
 275 aio_compute_timeout(AioContext *ctx)
 276 {
 277     BHListSlice *s;
 278     int64_t deadline;
 279     int timeout = -1;
 280
 281     timeout = aio_compute_bh_timeout(&ctx->bh_list, timeout);
 282     if (timeout == 0) {
 283         return 0;
 284     }
 285
 286     QSIMPLEQ_FOREACH(s, &ctx->bh_slice_list, next) {
 287         timeout = aio_compute_bh_timeout(&s->bh_list, timeout);
 288         if (timeout == 0) {
 289             return 0;
 290         }
 291     }
 292
 293     deadline = timerlistgroup_deadline_ns(&ctx->tlg);
 294     if (deadline == 0) {
 295         return 0;
 296     } else {
 297         return qemu_soonest_timeout(timeout, deadline);
 298     }
 299 }
 300
 301 static gboolean
 302 aio_ctx_prepare(GSource *source, gint    *timeout)
 303 {
 304     AioContext *ctx = (AioContext *) source;
 305
 306     qatomic_set(&ctx->notify_me, qatomic_read(&ctx->notify_me) | 1);
 307
 308     /*
 309      * Write ctx->notify_me before computing the timeout
 310      * (reading bottom half flags, etc.).  Pairs with
 311      * smp_mb in aio_notify().
 312      */
 313     smp_mb();
 314
 315     /* We assume there is no timeout already supplied */
 316     *timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx));
 317
 318     if (aio_prepare(ctx)) {
 319         *timeout = 0;
 320     }
 321
 322     return *timeout == 0;
 323 }
 324
 325 static gboolean
 326 aio_ctx_check(GSource *source)
 327 {
 328     AioContext *ctx = (AioContext *) source;
 329     QEMUBH *bh;
 330     BHListSlice *s;
 331
 332     /* Finish computing the timeout before clearing the flag.  */
 333     qatomic_store_release(&ctx->notify_me, qatomic_read(&ctx->notify_me) & ~1);
 334     aio_notify_accept(ctx);
 335
 336     QSLIST_FOREACH_RCU(bh, &ctx->bh_list, next) {
 337         if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
 338             return true;
 339         }
 340     }
 341
 342     QSIMPLEQ_FOREACH(s, &ctx->bh_slice_list, next) {
 343         QSLIST_FOREACH_RCU(bh, &s->bh_list, next) {
 344             if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
 345                 return true;
 346             }
 347         }
 348     }
 349     return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
 350 }
 351
 352 static gboolean
 353 aio_ctx_dispatch(GSource     *source,
 354                  GSourceFunc  callback,
 355                  gpointer     user_data)
 356 {
 357     AioContext *ctx = (AioContext *) source;
 358
 359     assert(callback == NULL);
 360     aio_dispatch(ctx);
 361     return true;
 362 }
 363
 364 static void
 365 aio_ctx_finalize(GSource     *source)
 366 {
 367     AioContext *ctx = (AioContext *) source;
 368     QEMUBH *bh;
 369     unsigned flags;
 370
 371     thread_pool_free(ctx->thread_pool);
 372
 373 #ifdef CONFIG_LINUX_AIO
 374     if (ctx->linux_aio) {
 375         laio_detach_aio_context(ctx->linux_aio, ctx);
 376         laio_cleanup(ctx->linux_aio);
 377         ctx->linux_aio = NULL;
 378     }
 379 #endif
 380
 381 #ifdef CONFIG_LINUX_IO_URING
 382     if (ctx->linux_io_uring) {
 383         luring_detach_aio_context(ctx->linux_io_uring, ctx);
 384         luring_cleanup(ctx->linux_io_uring);
 385         ctx->linux_io_uring = NULL;
 386     }
 387 #endif
 388
 389     assert(QSLIST_EMPTY(&ctx->scheduled_coroutines));
 390     qemu_bh_delete(ctx->co_schedule_bh);
 391
 392     /* There must be no aio_bh_poll() calls going on */
 393     assert(QSIMPLEQ_EMPTY(&ctx->bh_slice_list));
 394
 395     while ((bh = aio_bh_dequeue(&ctx->bh_list, &flags))) {
 396         /*
 397          * qemu_bh_delete() must have been called on BHs in this AioContext. In
 398          * many cases memory leaks, hangs, or inconsistent state occur when a
 399          * BH is leaked because something still expects it to run.
 400          *
 401          * If you hit this, fix the lifecycle of the BH so that
 402          * qemu_bh_delete() and any associated cleanup is called before the
 403          * AioContext is finalized.
 404          */
 405         if (unlikely(!(flags & BH_DELETED))) {
 406             fprintf(stderr, "%s: BH '%s' leaked, aborting...\n",
 407                     __func__, bh->name);
 408             abort();
 409         }
 410
 411         g_free(bh);
 412     }
 413
 414     aio_set_event_notifier(ctx, &ctx->notifier, NULL, NULL, NULL);
 415     event_notifier_cleanup(&ctx->notifier);
 416     qemu_rec_mutex_destroy(&ctx->lock);
 417     qemu_lockcnt_destroy(&ctx->list_lock);
 418     timerlistgroup_deinit(&ctx->tlg);
 419     unregister_aiocontext(ctx);
 420     aio_context_destroy(ctx);
 421 }
 422
 423 static GSourceFuncs aio_source_funcs = {
 424     aio_ctx_prepare,
 425     aio_ctx_check,
 426     aio_ctx_dispatch,
 427     aio_ctx_finalize
 428 };
 429
 430 GSource *aio_get_g_source(AioContext *ctx)
 431 {
 432     aio_context_use_g_source(ctx);
 433     g_source_ref(&ctx->source);
 434     return &ctx->source;
 435 }
 436
 437 ThreadPool *aio_get_thread_pool(AioContext *ctx)
 438 {
 439     if (!ctx->thread_pool) {
 440         ctx->thread_pool = thread_pool_new(ctx);
 441     }
 442     return ctx->thread_pool;
 443 }
 444
 445 #ifdef CONFIG_LINUX_AIO
 446 LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp)
 447 {
 448     if (!ctx->linux_aio) {
 449         ctx->linux_aio = laio_init(errp);
 450         if (ctx->linux_aio) {
 451             laio_attach_aio_context(ctx->linux_aio, ctx);
 452         }
 453     }
 454     return ctx->linux_aio;
 455 }
 456
 457 LinuxAioState *aio_get_linux_aio(AioContext *ctx)
 458 {
 459     assert(ctx->linux_aio);
 460     return ctx->linux_aio;
 461 }
 462 #endif
 463
 464 #ifdef CONFIG_LINUX_IO_URING
 465 LuringState *aio_setup_linux_io_uring(AioContext *ctx, Error **errp)
 466 {
 467     if (ctx->linux_io_uring) {
 468         return ctx->linux_io_uring;
 469     }
 470
 471     ctx->linux_io_uring = luring_init(errp);
 472     if (!ctx->linux_io_uring) {
 473         return NULL;
 474     }
 475
 476     luring_attach_aio_context(ctx->linux_io_uring, ctx);
 477     return ctx->linux_io_uring;
 478 }
 479
 480 LuringState *aio_get_linux_io_uring(AioContext *ctx)
 481 {
 482     assert(ctx->linux_io_uring);
 483     return ctx->linux_io_uring;
 484 }
 485 #endif
 486
 487 void aio_notify(AioContext *ctx)
 488 {
 489     /*
 490      * Write e.g. ctx->bh_list before writing ctx->notified.  Pairs with
 491      * smp_mb() in aio_notify_accept().
 492      */
 493     smp_wmb();
 494     qatomic_set(&ctx->notified, true);
 495
 496     /*
 497      * Write ctx->notified (and also ctx->bh_list) before reading ctx->notify_me.
 498      * Pairs with smp_mb() in aio_ctx_prepare or aio_poll.
 499      */
 500     smp_mb();
 501     if (qatomic_read(&ctx->notify_me)) {
 502         event_notifier_set(&ctx->notifier);
 503     }
 504 }
 505
 506 void aio_notify_accept(AioContext *ctx)
 507 {
 508     qatomic_set(&ctx->notified, false);
 509
 510     /*
 511      * Order reads of ctx->notified (in aio_context_notifier_poll()) and the
 512      * above clearing of ctx->notified before reads of e.g. bh->flags.  Pairs
 513      * with smp_wmb() in aio_notify.
 514      */
 515     smp_mb();
 516 }
 517
 518 static void aio_timerlist_notify(void *opaque, QEMUClockType type)
 519 {
 520     aio_notify(opaque);
 521 }
 522
 523 static void aio_context_notifier_cb(EventNotifier *e)
 524 {
 525     AioContext *ctx = container_of(e, AioContext, notifier);
 526
 527     event_notifier_test_and_clear(&ctx->notifier);
 528 }
 529
 530 /* Returns true if aio_notify() was called (e.g. a BH was scheduled) */
 531 static bool aio_context_notifier_poll(void *opaque)
 532 {
 533     EventNotifier *e = opaque;
 534     AioContext *ctx = container_of(e, AioContext, notifier);
 535
 536     /*
 537      * No need for load-acquire because we just want to kick the
 538      * event loop.  aio_notify_accept() takes care of synchronizing
 539      * the event loop with the producers.
 540      */
 541     return qatomic_read(&ctx->notified);
 542 }
 543
 544 static void aio_context_notifier_poll_ready(EventNotifier *e)
 545 {
 546     /* Do nothing, we just wanted to kick the event loop */
 547 }
 548
 549 static void co_schedule_bh_cb(void *opaque)
 550 {
 551     AioContext *ctx = opaque;
 552     QSLIST_HEAD(, Coroutine) straight, reversed;
 553
 554     QSLIST_MOVE_ATOMIC(&reversed, &ctx->scheduled_coroutines);
 555     QSLIST_INIT(&straight);
 556
 557     while (!QSLIST_EMPTY(&reversed)) {
 558         Coroutine *co = QSLIST_FIRST(&reversed);
 559         QSLIST_REMOVE_HEAD(&reversed, co_scheduled_next);
 560         QSLIST_INSERT_HEAD(&straight, co, co_scheduled_next);
 561     }
 562
 563     while (!QSLIST_EMPTY(&straight)) {
 564         Coroutine *co = QSLIST_FIRST(&straight);
 565         QSLIST_REMOVE_HEAD(&straight, co_scheduled_next);
 566         trace_aio_co_schedule_bh_cb(ctx, co);
 567
 568         /* Protected by write barrier in qemu_aio_coroutine_enter */
 569         qatomic_set(&co->scheduled, NULL);
 570         qemu_aio_coroutine_enter(ctx, co);
 571     }
 572 }
 573
 574 AioContext *aio_context_new(Error **errp)
 575 {
 576     int ret;
 577     AioContext *ctx;
 578
 579     ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
 580     QSLIST_INIT(&ctx->bh_list);
 581     QSIMPLEQ_INIT(&ctx->bh_slice_list);
 582     aio_context_setup(ctx);
 583
 584     ret = event_notifier_init(&ctx->notifier, false);
 585     if (ret < 0) {
 586         error_setg_errno(errp, -ret, "Failed to initialize event notifier");
 587         goto fail;
 588     }
 589     g_source_set_can_recurse(&ctx->source, true);
 590     qemu_lockcnt_init(&ctx->list_lock);
 591
 592     ctx->co_schedule_bh = aio_bh_new(ctx, co_schedule_bh_cb, ctx);
 593     QSLIST_INIT(&ctx->scheduled_coroutines);
 594
 595     aio_set_event_notifier(ctx, &ctx->notifier,
 596                            aio_context_notifier_cb,
 597                            aio_context_notifier_poll,
 598                            aio_context_notifier_poll_ready);
 599 #ifdef CONFIG_LINUX_AIO
 600     ctx->linux_aio = NULL;
 601 #endif
 602
 603 #ifdef CONFIG_LINUX_IO_URING
 604     ctx->linux_io_uring = NULL;
 605 #endif
 606
 607     ctx->thread_pool = NULL;
 608     qemu_rec_mutex_init(&ctx->lock);
 609     timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
 610
 611     ctx->poll_ns = 0;
 612     ctx->poll_max_ns = 0;
 613     ctx->poll_grow = 0;
 614     ctx->poll_shrink = 0;
 615
 616     ctx->aio_max_batch = 0;
 617
 618     ctx->thread_pool_min = 0;
 619     ctx->thread_pool_max = THREAD_POOL_MAX_THREADS_DEFAULT;
 620
 621     register_aiocontext(ctx);
 622
 623     return ctx;
 624 fail:
 625     g_source_destroy(&ctx->source);
 626     return NULL;
 627 }
 628
 629 void aio_co_schedule(AioContext *ctx, Coroutine *co)
 630 {
 631     trace_aio_co_schedule(ctx, co);
 632     const char *scheduled = qatomic_cmpxchg(&co->scheduled, NULL,
 633                                            __func__);
 634
 635     if (scheduled) {
 636         fprintf(stderr,
 637                 "%s: Co-routine was already scheduled in '%s'\n",
 638                 __func__, scheduled);
 639         abort();
 640     }
 641
 642     /* The coroutine might run and release the last ctx reference before we
 643      * invoke qemu_bh_schedule().  Take a reference to keep ctx alive until
 644      * we're done.
 645      */
 646     aio_context_ref(ctx);
 647
 648     QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines,
 649                               co, co_scheduled_next);
 650     qemu_bh_schedule(ctx->co_schedule_bh);
 651
 652     aio_context_unref(ctx);
 653 }
 654
 655 typedef struct AioCoRescheduleSelf {
 656     Coroutine *co;
 657     AioContext *new_ctx;
 658 } AioCoRescheduleSelf;
 659
 660 static void aio_co_reschedule_self_bh(void *opaque)
 661 {
 662     AioCoRescheduleSelf *data = opaque;
 663     aio_co_schedule(data->new_ctx, data->co);
 664 }
 665
 666 void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx)
 667 {
 668     AioContext *old_ctx = qemu_get_current_aio_context();
 669
 670     if (old_ctx != new_ctx) {
 671         AioCoRescheduleSelf data = {
 672             .co = qemu_coroutine_self(),
 673             .new_ctx = new_ctx,
 674         };
 675         /*
 676          * We can't directly schedule the coroutine in the target context
 677          * because this would be racy: The other thread could try to enter the
 678          * coroutine before it has yielded in this one.
 679          */
 680         aio_bh_schedule_oneshot(old_ctx, aio_co_reschedule_self_bh, &data);
 681         qemu_coroutine_yield();
 682     }
 683 }
 684
 685 void aio_co_wake(Coroutine *co)
 686 {
 687     AioContext *ctx;
 688
 689     /* Read coroutine before co->ctx.  Matches smp_wmb in
 690      * qemu_coroutine_enter.
 691      */
 692     smp_read_barrier_depends();
 693     ctx = qatomic_read(&co->ctx);
 694
 695     aio_co_enter(ctx, co);
 696 }
 697
 698 void aio_co_enter(AioContext *ctx, Coroutine *co)
 699 {
 700     if (ctx != qemu_get_current_aio_context()) {
 701         aio_co_schedule(ctx, co);
 702         return;
 703     }
 704
 705     if (qemu_in_coroutine()) {
 706         Coroutine *self = qemu_coroutine_self();
 707         assert(self != co);
 708         QSIMPLEQ_INSERT_TAIL(&self->co_queue_wakeup, co, co_queue_next);
 709     } else {
 710         qemu_aio_coroutine_enter(ctx, co);
 711     }
 712 }
 713
 714 void aio_context_ref(AioContext *ctx)
 715 {
 716     g_source_ref(&ctx->source);
 717 }
 718
 719 void aio_context_unref(AioContext *ctx)
 720 {
 721     g_source_unref(&ctx->source);
 722 }
 723
 724 QEMU_DEFINE_STATIC_CO_TLS(AioContext *, my_aiocontext)
 725
 726 AioContext *qemu_get_current_aio_context(void)
 727 {
 728     AioContext *ctx = get_my_aiocontext();
 729     if (ctx) {
 730         return ctx;
 731     }
 732     if (bql_locked()) {
 733         /* Possibly in a vCPU thread.  */
 734         return qemu_get_aio_context();
 735     }
 736     return NULL;
 737 }
 738
 739 void qemu_set_current_aio_context(AioContext *ctx)
 740 {
 741     assert(!get_my_aiocontext());
 742     set_my_aiocontext(ctx);
 743 }
 744
 745 void aio_context_set_thread_pool_params(AioContext *ctx, int64_t min,
 746                                         int64_t max, Error **errp)
 747 {
 748
 749     if (min > max || !max || min > INT_MAX || max > INT_MAX) {
 750         error_setg(errp, "bad thread-pool-min/thread-pool-max values");
 751         return;
 752     }
 753
 754     ctx->thread_pool_min = min;
 755     ctx->thread_pool_max = max;
 756
 757     if (ctx->thread_pool) {
 758         thread_pool_update_params(ctx->thread_pool, ctx);
 759     }
 760 }