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/*
* Helper functionality for distributing a fixed total amount of
* an abstract resource among multiple coroutines.
*
* Copyright (c) 2019 Virtuozzo International GmbH
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu/osdep.h"
#include "qemu/coroutine.h"
#include "qemu/co-shared-resource.h"
struct SharedResource {
uint64_t total; /* Set in shres_create() and not changed anymore */
/* State fields protected by lock */
uint64_t available;
CoQueue queue;
QemuMutex lock;
};
SharedResource *shres_create(uint64_t total)
{
SharedResource *s = g_new0(SharedResource, 1);
s->total = s->available = total;
qemu_co_queue_init(&s->queue);
qemu_mutex_init(&s->lock);
return s;
}
void shres_destroy(SharedResource *s)
{
assert(s->available == s->total);
qemu_mutex_destroy(&s->lock);
g_free(s);
}
/* Called with lock held. */
static bool co_try_get_from_shres_locked(SharedResource *s, uint64_t n)
{
if (s->available >= n) {
s->available -= n;
return true;
}
return false;
}
void coroutine_fn co_get_from_shres(SharedResource *s, uint64_t n)
{
assert(n <= s->total);
QEMU_LOCK_GUARD(&s->lock);
while (!co_try_get_from_shres_locked(s, n)) {
qemu_co_queue_wait(&s->queue, &s->lock);
}
}
void coroutine_fn co_put_to_shres(SharedResource *s, uint64_t n)
{
QEMU_LOCK_GUARD(&s->lock);
assert(s->total - s->available >= n);
s->available += n;
qemu_co_queue_restart_all(&s->queue);
}
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