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; /* Set in shres_create() and not changed anymore */
  32
  33    /* State fields protected by lock */
  34    uint64_t available;
  35    CoQueue queue;
  36
  37    QemuMutex lock;
  38};
  39
  40SharedResource *shres_create(uint64_t total)
  41{
  42    SharedResource *s = g_new0(SharedResource, 1);
  43
  44    s->total = s->available = total;
  45    qemu_co_queue_init(&s->queue);
  46    qemu_mutex_init(&s->lock);
  47
  48    return s;
  49}
  50
  51void shres_destroy(SharedResource *s)
  52{
  53    assert(s->available == s->total);
  54    qemu_mutex_destroy(&s->lock);
  55    g_free(s);
  56}
  57
  58/* Called with lock held. */
  59static bool co_try_get_from_shres_locked(SharedResource *s, uint64_t n)
  60{
  61    if (s->available >= n) {
  62        s->available -= n;
  63        return true;
  64    }
  65
  66    return false;
  67}
  68
  69bool co_try_get_from_shres(SharedResource *s, uint64_t n)
  70{
  71    QEMU_LOCK_GUARD(&s->lock);
  72    return co_try_get_from_shres_locked(s, n);
  73}
  74
  75void coroutine_fn co_get_from_shres(SharedResource *s, uint64_t n)
  76{
  77    assert(n <= s->total);
  78    QEMU_LOCK_GUARD(&s->lock);
  79    while (!co_try_get_from_shres_locked(s, n)) {
  80        qemu_co_queue_wait(&s->queue, &s->lock);
  81    }
  82}
  83
  84void coroutine_fn co_put_to_shres(SharedResource *s, uint64_t n)
  85{
  86    QEMU_LOCK_GUARD(&s->lock);
  87    assert(s->total - s->available >= n);
  88    s->available += n;
  89    qemu_co_queue_restart_all(&s->queue);
  90}
  91