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 } 91