qemu

FORK: QEMU emulator
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qemu-co-shared-resource.c (2690B)

      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 
     30 struct 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 
     40 SharedResource *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 
     51 void 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. */
     59 static 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 
     69 bool 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 
     75 void 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 
     84 void 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 }