util/aio-wait.c

   1 /*
   2  * AioContext wait support
   3  *
   4  * Copyright (C) 2018 Red Hat, Inc.
   5  *
   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:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  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
  22  * THE SOFTWARE.
  23  */
  24
  25 #include "qemu/osdep.h"
  26 #include "qemu/main-loop.h"
  27 #include "block/aio-wait.h"
  28
  29 static void dummy_bh_cb(void *opaque)
  30 {
  31     /* The point is to make AIO_WAIT_WHILE()'s aio_poll() return */
  32 }
  33
  34 void aio_wait_kick(AioWait *wait)
  35 {
  36     /* The barrier (or an atomic op) is in the caller.  */
  37     if (atomic_read(&wait->num_waiters)) {
  38         aio_bh_schedule_oneshot(qemu_get_aio_context(), dummy_bh_cb, NULL);
  39     }
  40 }
  41
  42 typedef struct {
  43     AioWait wait;
  44     bool done;
  45     QEMUBHFunc *cb;
  46     void *opaque;
  47 } AioWaitBHData;
  48
  49 /* Context: BH in IOThread */
  50 static void aio_wait_bh(void *opaque)
  51 {
  52     AioWaitBHData *data = opaque;
  53
  54     data->cb(data->opaque);
  55
  56     data->done = true;
  57     aio_wait_kick(&data->wait);
  58 }
  59
  60 void aio_wait_bh_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
  61 {
  62     AioWaitBHData data = {
  63         .cb = cb,
  64         .opaque = opaque,
  65     };
  66
  67     assert(qemu_get_current_aio_context() == qemu_get_aio_context());
  68
  69     aio_bh_schedule_oneshot(ctx, aio_wait_bh, &data);
  70     AIO_WAIT_WHILE(&data.wait, ctx, !data.done);
  71 }