LXR qemu/util/qemu-co-shared-resource.c

   1/*
   2 * Helper functionality for distributing a fixed total amount of
   3 * an abstract resource among multiple coroutines.
   4 *
   5 * Copyright (c) 2019 Virtuozzo International GmbH
   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 "qemu/coroutine.h"
  28#include "qemu/co-shared-resource.h"
  29
  30struct SharedResource {
  31    uint64_t total;
  32    uint64_t available;
  33
  34    CoQueue queue;
  35};
  36
  37SharedResource *shres_create(uint64_t total)
  38{
  39    SharedResource *s = g_new0(SharedResource, 1);
  40
  41    s->total = s->available = total;
  42    qemu_co_queue_init(&s->queue);
  43
  44    return s;
  45}
  46
  47void shres_destroy(SharedResource *s)
  48{
  49    assert(s->available == s->total);
  50    g_free(s);
  51}
  52
  53bool co_try_get_from_shres(SharedResource *s, uint64_t n)
  54{
  55    if (s->available >= n) {
  56        s->available -= n;
  57        return true;
  58    }
  59
  60    return false;
  61}
  62
  63void coroutine_fn co_get_from_shres(SharedResource *s, uint64_t n)
  64{
  65    assert(n <= s->total);
  66    while (!co_try_get_from_shres(s, n)) {
  67        qemu_co_queue_wait(&s->queue, NULL);
  68    }
  69}
  70
  71void coroutine_fn co_put_to_shres(SharedResource *s, uint64_t n)
  72{
  73    assert(s->total - s->available >= n);
  74    s->available += n;
  75    qemu_co_queue_restart_all(&s->queue);
  76}
  77