util/aio-posix.c

   1 /*
   2  * QEMU aio implementation
   3  *
   4  * Copyright IBM, Corp. 2008
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  *
  12  * Contributions after 2012-01-13 are licensed under the terms of the
  13  * GNU GPL, version 2 or (at your option) any later version.
  14  */
  15
  16 #include "qemu/osdep.h"
  17 #include "block/block.h"
  18 #include "qemu/rcu_queue.h"
  19 #include "qemu/sockets.h"
  20 #include "qemu/cutils.h"
  21 #include "trace.h"
  22 #ifdef CONFIG_EPOLL_CREATE1
  23 #include <sys/epoll.h>
  24 #endif
  25
  26 struct AioHandler
  27 {
  28     GPollFD pfd;
  29     IOHandler *io_read;
  30     IOHandler *io_write;
  31     AioPollFn *io_poll;
  32     IOHandler *io_poll_begin;
  33     IOHandler *io_poll_end;
  34     int deleted;
  35     void *opaque;
  36     bool is_external;
  37     QLIST_ENTRY(AioHandler) node;
  38 };
  39
  40 #ifdef CONFIG_EPOLL_CREATE1
  41
  42 /* The fd number threshold to switch to epoll */
  43 #define EPOLL_ENABLE_THRESHOLD 64
  44
  45 static void aio_epoll_disable(AioContext *ctx)
  46 {
  47     ctx->epoll_enabled = false;
  48     if (!ctx->epoll_available) {
  49         return;
  50     }
  51     ctx->epoll_available = false;
  52     close(ctx->epollfd);
  53 }
  54
  55 static inline int epoll_events_from_pfd(int pfd_events)
  56 {
  57     return (pfd_events & G_IO_IN ? EPOLLIN : 0) |
  58            (pfd_events & G_IO_OUT ? EPOLLOUT : 0) |
  59            (pfd_events & G_IO_HUP ? EPOLLHUP : 0) |
  60            (pfd_events & G_IO_ERR ? EPOLLERR : 0);
  61 }
  62
  63 static bool aio_epoll_try_enable(AioContext *ctx)
  64 {
  65     AioHandler *node;
  66     struct epoll_event event;
  67
  68     QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
  69         int r;
  70         if (node->deleted || !node->pfd.events) {
  71             continue;
  72         }
  73         event.events = epoll_events_from_pfd(node->pfd.events);
  74         event.data.ptr = node;
  75         r = epoll_ctl(ctx->epollfd, EPOLL_CTL_ADD, node->pfd.fd, &event);
  76         if (r) {
  77             return false;
  78         }
  79     }
  80     ctx->epoll_enabled = true;
  81     return true;
  82 }
  83
  84 static void aio_epoll_update(AioContext *ctx, AioHandler *node, bool is_new)
  85 {
  86     struct epoll_event event;
  87     int r;
  88     int ctl;
  89
  90     if (!ctx->epoll_enabled) {
  91         return;
  92     }
  93     if (!node->pfd.events) {
  94         ctl = EPOLL_CTL_DEL;
  95     } else {
  96         event.data.ptr = node;
  97         event.events = epoll_events_from_pfd(node->pfd.events);
  98         ctl = is_new ? EPOLL_CTL_ADD : EPOLL_CTL_MOD;
  99     }
 100
 101     r = epoll_ctl(ctx->epollfd, ctl, node->pfd.fd, &event);
 102     if (r) {
 103         aio_epoll_disable(ctx);
 104     }
 105 }
 106
 107 static int aio_epoll(AioContext *ctx, GPollFD *pfds,
 108                      unsigned npfd, int64_t timeout)
 109 {
 110     AioHandler *node;
 111     int i, ret = 0;
 112     struct epoll_event events[128];
 113
 114     assert(npfd == 1);
 115     assert(pfds[0].fd == ctx->epollfd);
 116     if (timeout > 0) {
 117         ret = qemu_poll_ns(pfds, npfd, timeout);
 118     }
 119     if (timeout <= 0 || ret > 0) {
 120         ret = epoll_wait(ctx->epollfd, events,
 121                          ARRAY_SIZE(events),
 122                          timeout);
 123         if (ret <= 0) {
 124             goto out;
 125         }
 126         for (i = 0; i < ret; i++) {
 127             int ev = events[i].events;
 128             node = events[i].data.ptr;
 129             node->pfd.revents = (ev & EPOLLIN ? G_IO_IN : 0) |
 130                 (ev & EPOLLOUT ? G_IO_OUT : 0) |
 131                 (ev & EPOLLHUP ? G_IO_HUP : 0) |
 132                 (ev & EPOLLERR ? G_IO_ERR : 0);
 133         }
 134     }
 135 out:
 136     return ret;
 137 }
 138
 139 static bool aio_epoll_enabled(AioContext *ctx)
 140 {
 141     /* Fall back to ppoll when external clients are disabled. */
 142     return !aio_external_disabled(ctx) && ctx->epoll_enabled;
 143 }
 144
 145 static bool aio_epoll_check_poll(AioContext *ctx, GPollFD *pfds,
 146                                  unsigned npfd, int64_t timeout)
 147 {
 148     if (!ctx->epoll_available) {
 149         return false;
 150     }
 151     if (aio_epoll_enabled(ctx)) {
 152         return true;
 153     }
 154     if (npfd >= EPOLL_ENABLE_THRESHOLD) {
 155         if (aio_epoll_try_enable(ctx)) {
 156             return true;
 157         } else {
 158             aio_epoll_disable(ctx);
 159         }
 160     }
 161     return false;
 162 }
 163
 164 #else
 165
 166 static void aio_epoll_update(AioContext *ctx, AioHandler *node, bool is_new)
 167 {
 168 }
 169
 170 static int aio_epoll(AioContext *ctx, GPollFD *pfds,
 171                      unsigned npfd, int64_t timeout)
 172 {
 173     assert(false);
 174 }
 175
 176 static bool aio_epoll_enabled(AioContext *ctx)
 177 {
 178     return false;
 179 }
 180
 181 static bool aio_epoll_check_poll(AioContext *ctx, GPollFD *pfds,
 182                           unsigned npfd, int64_t timeout)
 183 {
 184     return false;
 185 }
 186
 187 #endif
 188
 189 static AioHandler *find_aio_handler(AioContext *ctx, int fd)
 190 {
 191     AioHandler *node;
 192
 193     QLIST_FOREACH(node, &ctx->aio_handlers, node) {
 194         if (node->pfd.fd == fd)
 195             if (!node->deleted)
 196                 return node;
 197     }
 198
 199     return NULL;
 200 }
 201
 202 static bool aio_remove_fd_handler(AioContext *ctx, AioHandler *node)
 203 {
 204     /* If the GSource is in the process of being destroyed then
 205      * g_source_remove_poll() causes an assertion failure.  Skip
 206      * removal in that case, because glib cleans up its state during
 207      * destruction anyway.
 208      */
 209     if (!g_source_is_destroyed(&ctx->source)) {
 210         g_source_remove_poll(&ctx->source, &node->pfd);
 211     }
 212
 213     /* If a read is in progress, just mark the node as deleted */
 214     if (qemu_lockcnt_count(&ctx->list_lock)) {
 215         node->deleted = 1;
 216         node->pfd.revents = 0;
 217         return false;
 218     }
 219     /* Otherwise, delete it for real.  We can't just mark it as
 220      * deleted because deleted nodes are only cleaned up while
 221      * no one is walking the handlers list.
 222      */
 223     QLIST_REMOVE(node, node);
 224     return true;
 225 }
 226
 227 void aio_set_fd_handler(AioContext *ctx,
 228                         int fd,
 229                         bool is_external,
 230                         IOHandler *io_read,
 231                         IOHandler *io_write,
 232                         AioPollFn *io_poll,
 233                         void *opaque)
 234 {
 235     AioHandler *node;
 236     AioHandler *new_node = NULL;
 237     bool is_new = false;
 238     bool deleted = false;
 239     int poll_disable_change;
 240
 241     qemu_lockcnt_lock(&ctx->list_lock);
 242
 243     node = find_aio_handler(ctx, fd);
 244
 245     /* Are we deleting the fd handler? */
 246     if (!io_read && !io_write && !io_poll) {
 247         if (node == NULL) {
 248             qemu_lockcnt_unlock(&ctx->list_lock);
 249             return;
 250         }
 251         /* Clean events in order to unregister fd from the ctx epoll. */
 252         node->pfd.events = 0;
 253
 254         poll_disable_change = -!node->io_poll;
 255     } else {
 256         poll_disable_change = !io_poll - (node && !node->io_poll);
 257         if (node == NULL) {
 258             is_new = true;
 259         }
 260         /* Alloc and insert if it's not already there */
 261         new_node = g_new0(AioHandler, 1);
 262
 263         /* Update handler with latest information */
 264         new_node->io_read = io_read;
 265         new_node->io_write = io_write;
 266         new_node->io_poll = io_poll;
 267         new_node->opaque = opaque;
 268         new_node->is_external = is_external;
 269
 270         if (is_new) {
 271             new_node->pfd.fd = fd;
 272         } else {
 273             new_node->pfd = node->pfd;
 274         }
 275         g_source_add_poll(&ctx->source, &new_node->pfd);
 276
 277         new_node->pfd.events = (io_read ? G_IO_IN | G_IO_HUP | G_IO_ERR : 0);
 278         new_node->pfd.events |= (io_write ? G_IO_OUT | G_IO_ERR : 0);
 279
 280         QLIST_INSERT_HEAD_RCU(&ctx->aio_handlers, new_node, node);
 281     }
 282     if (node) {
 283         deleted = aio_remove_fd_handler(ctx, node);
 284     }
 285
 286     /* No need to order poll_disable_cnt writes against other updates;
 287      * the counter is only used to avoid wasting time and latency on
 288      * iterated polling when the system call will be ultimately necessary.
 289      * Changing handlers is a rare event, and a little wasted polling until
 290      * the aio_notify below is not an issue.
 291      */
 292     atomic_set(&ctx->poll_disable_cnt,
 293                atomic_read(&ctx->poll_disable_cnt) + poll_disable_change);
 294
 295     if (new_node) {
 296         aio_epoll_update(ctx, new_node, is_new);
 297     } else if (node) {
 298         /* Unregister deleted fd_handler */
 299         aio_epoll_update(ctx, node, false);
 300     }
 301     qemu_lockcnt_unlock(&ctx->list_lock);
 302     aio_notify(ctx);
 303
 304     if (deleted) {
 305         g_free(node);
 306     }
 307 }
 308
 309 void aio_set_fd_poll(AioContext *ctx, int fd,
 310                      IOHandler *io_poll_begin,
 311                      IOHandler *io_poll_end)
 312 {
 313     AioHandler *node = find_aio_handler(ctx, fd);
 314
 315     if (!node) {
 316         return;
 317     }
 318
 319     node->io_poll_begin = io_poll_begin;
 320     node->io_poll_end = io_poll_end;
 321 }
 322
 323 void aio_set_event_notifier(AioContext *ctx,
 324                             EventNotifier *notifier,
 325                             bool is_external,
 326                             EventNotifierHandler *io_read,
 327                             AioPollFn *io_poll)
 328 {
 329     aio_set_fd_handler(ctx, event_notifier_get_fd(notifier), is_external,
 330                        (IOHandler *)io_read, NULL, io_poll, notifier);
 331 }
 332
 333 void aio_set_event_notifier_poll(AioContext *ctx,
 334                                  EventNotifier *notifier,
 335                                  EventNotifierHandler *io_poll_begin,
 336                                  EventNotifierHandler *io_poll_end)
 337 {
 338     aio_set_fd_poll(ctx, event_notifier_get_fd(notifier),
 339                     (IOHandler *)io_poll_begin,
 340                     (IOHandler *)io_poll_end);
 341 }
 342
 343 static void poll_set_started(AioContext *ctx, bool started)
 344 {
 345     AioHandler *node;
 346
 347     if (started == ctx->poll_started) {
 348         return;
 349     }
 350
 351     ctx->poll_started = started;
 352
 353     qemu_lockcnt_inc(&ctx->list_lock);
 354     QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
 355         IOHandler *fn;
 356
 357         if (node->deleted) {
 358             continue;
 359         }
 360
 361         if (started) {
 362             fn = node->io_poll_begin;
 363         } else {
 364             fn = node->io_poll_end;
 365         }
 366
 367         if (fn) {
 368             fn(node->opaque);
 369         }
 370     }
 371     qemu_lockcnt_dec(&ctx->list_lock);
 372 }
 373
 374
 375 bool aio_prepare(AioContext *ctx)
 376 {
 377     /* Poll mode cannot be used with glib's event loop, disable it. */
 378     poll_set_started(ctx, false);
 379
 380     return false;
 381 }
 382
 383 bool aio_pending(AioContext *ctx)
 384 {
 385     AioHandler *node;
 386     bool result = false;
 387
 388     /*
 389      * We have to walk very carefully in case aio_set_fd_handler is
 390      * called while we're walking.
 391      */
 392     qemu_lockcnt_inc(&ctx->list_lock);
 393
 394     QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
 395         int revents;
 396
 397         revents = node->pfd.revents & node->pfd.events;
 398         if (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR) && node->io_read &&
 399             aio_node_check(ctx, node->is_external)) {
 400             result = true;
 401             break;
 402         }
 403         if (revents & (G_IO_OUT | G_IO_ERR) && node->io_write &&
 404             aio_node_check(ctx, node->is_external)) {
 405             result = true;
 406             break;
 407         }
 408     }
 409     qemu_lockcnt_dec(&ctx->list_lock);
 410
 411     return result;
 412 }
 413
 414 static bool aio_dispatch_handlers(AioContext *ctx)
 415 {
 416     AioHandler *node, *tmp;
 417     bool progress = false;
 418
 419     QLIST_FOREACH_SAFE_RCU(node, &ctx->aio_handlers, node, tmp) {
 420         int revents;
 421
 422         revents = node->pfd.revents & node->pfd.events;
 423         node->pfd.revents = 0;
 424
 425         if (!node->deleted &&
 426             (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR)) &&
 427             aio_node_check(ctx, node->is_external) &&
 428             node->io_read) {
 429             node->io_read(node->opaque);
 430
 431             /* aio_notify() does not count as progress */
 432             if (node->opaque != &ctx->notifier) {
 433                 progress = true;
 434             }
 435         }
 436         if (!node->deleted &&
 437             (revents & (G_IO_OUT | G_IO_ERR)) &&
 438             aio_node_check(ctx, node->is_external) &&
 439             node->io_write) {
 440             node->io_write(node->opaque);
 441             progress = true;
 442         }
 443
 444         if (node->deleted) {
 445             if (qemu_lockcnt_dec_if_lock(&ctx->list_lock)) {
 446                 QLIST_REMOVE(node, node);
 447                 g_free(node);
 448                 qemu_lockcnt_inc_and_unlock(&ctx->list_lock);
 449             }
 450         }
 451     }
 452
 453     return progress;
 454 }
 455
 456 void aio_dispatch(AioContext *ctx)
 457 {
 458     qemu_lockcnt_inc(&ctx->list_lock);
 459     aio_bh_poll(ctx);
 460     aio_dispatch_handlers(ctx);
 461     qemu_lockcnt_dec(&ctx->list_lock);
 462
 463     timerlistgroup_run_timers(&ctx->tlg);
 464 }
 465
 466 /* These thread-local variables are used only in a small part of aio_poll
 467  * around the call to the poll() system call.  In particular they are not
 468  * used while aio_poll is performing callbacks, which makes it much easier
 469  * to think about reentrancy!
 470  *
 471  * Stack-allocated arrays would be perfect but they have size limitations;
 472  * heap allocation is expensive enough that we want to reuse arrays across
 473  * calls to aio_poll().  And because poll() has to be called without holding
 474  * any lock, the arrays cannot be stored in AioContext.  Thread-local data
 475  * has none of the disadvantages of these three options.
 476  */
 477 static __thread GPollFD *pollfds;
 478 static __thread AioHandler **nodes;
 479 static __thread unsigned npfd, nalloc;
 480 static __thread Notifier pollfds_cleanup_notifier;
 481
 482 static void pollfds_cleanup(Notifier *n, void *unused)
 483 {
 484     g_assert(npfd == 0);
 485     g_free(pollfds);
 486     g_free(nodes);
 487     nalloc = 0;
 488 }
 489
 490 static void add_pollfd(AioHandler *node)
 491 {
 492     if (npfd == nalloc) {
 493         if (nalloc == 0) {
 494             pollfds_cleanup_notifier.notify = pollfds_cleanup;
 495             qemu_thread_atexit_add(&pollfds_cleanup_notifier);
 496             nalloc = 8;
 497         } else {
 498             g_assert(nalloc <= INT_MAX);
 499             nalloc *= 2;
 500         }
 501         pollfds = g_renew(GPollFD, pollfds, nalloc);
 502         nodes = g_renew(AioHandler *, nodes, nalloc);
 503     }
 504     nodes[npfd] = node;
 505     pollfds[npfd] = (GPollFD) {
 506         .fd = node->pfd.fd,
 507         .events = node->pfd.events,
 508     };
 509     npfd++;
 510 }
 511
 512 static bool run_poll_handlers_once(AioContext *ctx, int64_t *timeout)
 513 {
 514     bool progress = false;
 515     AioHandler *node;
 516
 517     QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
 518         if (!node->deleted && node->io_poll &&
 519             aio_node_check(ctx, node->is_external) &&
 520             node->io_poll(node->opaque)) {
 521             /*
 522              * Polling was successful, exit try_poll_mode immediately
 523              * to adjust the next polling time.
 524              */
 525             *timeout = 0;
 526             if (node->opaque != &ctx->notifier) {
 527                 progress = true;
 528             }
 529         }
 530
 531         /* Caller handles freeing deleted nodes.  Don't do it here. */
 532     }
 533
 534     return progress;
 535 }
 536
 537 /* run_poll_handlers:
 538  * @ctx: the AioContext
 539  * @max_ns: maximum time to poll for, in nanoseconds
 540  *
 541  * Polls for a given time.
 542  *
 543  * Note that ctx->notify_me must be non-zero so this function can detect
 544  * aio_notify().
 545  *
 546  * Note that the caller must have incremented ctx->list_lock.
 547  *
 548  * Returns: true if progress was made, false otherwise
 549  */
 550 static bool run_poll_handlers(AioContext *ctx, int64_t max_ns, int64_t *timeout)
 551 {
 552     bool progress;
 553     int64_t start_time, elapsed_time;
 554
 555     assert(ctx->notify_me);
 556     assert(qemu_lockcnt_count(&ctx->list_lock) > 0);
 557
 558     trace_run_poll_handlers_begin(ctx, max_ns, *timeout);
 559
 560     start_time = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
 561     do {
 562         progress = run_poll_handlers_once(ctx, timeout);
 563         elapsed_time = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - start_time;
 564         max_ns = qemu_soonest_timeout(*timeout, max_ns);
 565         assert(!(max_ns && progress));
 566     } while (elapsed_time < max_ns && !atomic_read(&ctx->poll_disable_cnt));
 567
 568     /* If time has passed with no successful polling, adjust *timeout to
 569      * keep the same ending time.
 570      */
 571     if (*timeout != -1) {
 572         *timeout -= MIN(*timeout, elapsed_time);
 573     }
 574
 575     trace_run_poll_handlers_end(ctx, progress, *timeout);
 576     return progress;
 577 }
 578
 579 /* try_poll_mode:
 580  * @ctx: the AioContext
 581  * @timeout: timeout for blocking wait, computed by the caller and updated if
 582  *    polling succeeds.
 583  *
 584  * ctx->notify_me must be non-zero so this function can detect aio_notify().
 585  *
 586  * Note that the caller must have incremented ctx->list_lock.
 587  *
 588  * Returns: true if progress was made, false otherwise
 589  */
 590 static bool try_poll_mode(AioContext *ctx, int64_t *timeout)
 591 {
 592     int64_t max_ns = qemu_soonest_timeout(*timeout, ctx->poll_ns);
 593
 594     if (max_ns && !atomic_read(&ctx->poll_disable_cnt)) {
 595         poll_set_started(ctx, true);
 596
 597         if (run_poll_handlers(ctx, max_ns, timeout)) {
 598             return true;
 599         }
 600     }
 601
 602     poll_set_started(ctx, false);
 603
 604     /* Even if we don't run busy polling, try polling once in case it can make
 605      * progress and the caller will be able to avoid ppoll(2)/epoll_wait(2).
 606      */
 607     return run_poll_handlers_once(ctx, timeout);
 608 }
 609
 610 bool aio_poll(AioContext *ctx, bool blocking)
 611 {
 612     AioHandler *node;
 613     int i;
 614     int ret = 0;
 615     bool progress;
 616     int64_t timeout;
 617     int64_t start = 0;
 618
 619     assert(in_aio_context_home_thread(ctx));
 620
 621     /* aio_notify can avoid the expensive event_notifier_set if
 622      * everything (file descriptors, bottom halves, timers) will
 623      * be re-evaluated before the next blocking poll().  This is
 624      * already true when aio_poll is called with blocking == false;
 625      * if blocking == true, it is only true after poll() returns,
 626      * so disable the optimization now.
 627      */
 628     if (blocking) {
 629         atomic_add(&ctx->notify_me, 2);
 630     }
 631
 632     qemu_lockcnt_inc(&ctx->list_lock);
 633
 634     if (ctx->poll_max_ns) {
 635         start = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
 636     }
 637
 638     timeout = blocking ? aio_compute_timeout(ctx) : 0;
 639     progress = try_poll_mode(ctx, &timeout);
 640     assert(!(timeout && progress));
 641
 642     /* If polling is allowed, non-blocking aio_poll does not need the
 643      * system call---a single round of run_poll_handlers_once suffices.
 644      */
 645     if (timeout || atomic_read(&ctx->poll_disable_cnt)) {
 646         assert(npfd == 0);
 647
 648         /* fill pollfds */
 649
 650         if (!aio_epoll_enabled(ctx)) {
 651             QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
 652                 if (!node->deleted && node->pfd.events
 653                     && aio_node_check(ctx, node->is_external)) {
 654                     add_pollfd(node);
 655                 }
 656             }
 657         }
 658
 659         /* wait until next event */
 660         if (aio_epoll_check_poll(ctx, pollfds, npfd, timeout)) {
 661             AioHandler epoll_handler;
 662
 663             epoll_handler.pfd.fd = ctx->epollfd;
 664             epoll_handler.pfd.events = G_IO_IN | G_IO_OUT | G_IO_HUP | G_IO_ERR;
 665             npfd = 0;
 666             add_pollfd(&epoll_handler);
 667             ret = aio_epoll(ctx, pollfds, npfd, timeout);
 668         } else  {
 669             ret = qemu_poll_ns(pollfds, npfd, timeout);
 670         }
 671     }
 672
 673     if (blocking) {
 674         atomic_sub(&ctx->notify_me, 2);
 675         aio_notify_accept(ctx);
 676     }
 677
 678     /* Adjust polling time */
 679     if (ctx->poll_max_ns) {
 680         int64_t block_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - start;
 681
 682         if (block_ns <= ctx->poll_ns) {
 683             /* This is the sweet spot, no adjustment needed */
 684         } else if (block_ns > ctx->poll_max_ns) {
 685             /* We'd have to poll for too long, poll less */
 686             int64_t old = ctx->poll_ns;
 687
 688             if (ctx->poll_shrink) {
 689                 ctx->poll_ns /= ctx->poll_shrink;
 690             } else {
 691                 ctx->poll_ns = 0;
 692             }
 693
 694             trace_poll_shrink(ctx, old, ctx->poll_ns);
 695         } else if (ctx->poll_ns < ctx->poll_max_ns &&
 696                    block_ns < ctx->poll_max_ns) {
 697             /* There is room to grow, poll longer */
 698             int64_t old = ctx->poll_ns;
 699             int64_t grow = ctx->poll_grow;
 700
 701             if (grow == 0) {
 702                 grow = 2;
 703             }
 704
 705             if (ctx->poll_ns) {
 706                 ctx->poll_ns *= grow;
 707             } else {
 708                 ctx->poll_ns = 4000; /* start polling at 4 microseconds */
 709             }
 710
 711             if (ctx->poll_ns > ctx->poll_max_ns) {
 712                 ctx->poll_ns = ctx->poll_max_ns;
 713             }
 714
 715             trace_poll_grow(ctx, old, ctx->poll_ns);
 716         }
 717     }
 718
 719     /* if we have any readable fds, dispatch event */
 720     if (ret > 0) {
 721         for (i = 0; i < npfd; i++) {
 722             nodes[i]->pfd.revents = pollfds[i].revents;
 723         }
 724     }
 725
 726     npfd = 0;
 727
 728     progress |= aio_bh_poll(ctx);
 729
 730     if (ret > 0) {
 731         progress |= aio_dispatch_handlers(ctx);
 732     }
 733
 734     qemu_lockcnt_dec(&ctx->list_lock);
 735
 736     progress |= timerlistgroup_run_timers(&ctx->tlg);
 737
 738     return progress;
 739 }
 740
 741 void aio_context_setup(AioContext *ctx)
 742 {
 743 #ifdef CONFIG_EPOLL_CREATE1
 744     assert(!ctx->epollfd);
 745     ctx->epollfd = epoll_create1(EPOLL_CLOEXEC);
 746     if (ctx->epollfd == -1) {
 747         fprintf(stderr, "Failed to create epoll instance: %s", strerror(errno));
 748         ctx->epoll_available = false;
 749     } else {
 750         ctx->epoll_available = true;
 751     }
 752 #endif
 753 }
 754
 755 void aio_context_destroy(AioContext *ctx)
 756 {
 757 #ifdef CONFIG_EPOLL_CREATE1
 758     aio_epoll_disable(ctx);
 759 #endif
 760 }
 761
 762 void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
 763                                  int64_t grow, int64_t shrink, Error **errp)
 764 {
 765     /* No thread synchronization here, it doesn't matter if an incorrect value
 766      * is used once.
 767      */
 768     ctx->poll_max_ns = max_ns;
 769     ctx->poll_ns = 0;
 770     ctx->poll_grow = grow;
 771     ctx->poll_shrink = shrink;
 772
 773     aio_notify(ctx);
 774 }