include/qemu/co-shared-resource.h

   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 #ifndef QEMU_CO_SHARED_RESOURCE_H
  27 #define QEMU_CO_SHARED_RESOURCE_H
  28
  29
  30 typedef struct SharedResource SharedResource;
  31
  32 /*
  33  * Create SharedResource structure
  34  *
  35  * @total: total amount of some resource to be shared between clients
  36  *
  37  * Note: this API is not thread-safe.
  38  */
  39 SharedResource *shres_create(uint64_t total);
  40
  41 /*
  42  * Release SharedResource structure
  43  *
  44  * This function may only be called once everything allocated by all
  45  * clients has been deallocated.
  46  */
  47 void shres_destroy(SharedResource *s);
  48
  49 /*
  50  * Try to allocate an amount of @n.  Return true on success, and false
  51  * if there is too little left of the collective resource to fulfill
  52  * the request.
  53  */
  54 bool co_try_get_from_shres(SharedResource *s, uint64_t n);
  55
  56 /*
  57  * Allocate an amount of @n, and, if necessary, yield until
  58  * that becomes possible.
  59  */
  60 void coroutine_fn co_get_from_shres(SharedResource *s, uint64_t n);
  61
  62 /*
  63  * Deallocate an amount of @n.  The total amount allocated by a caller
  64  * does not need to be deallocated/released with a single call, but may
  65  * be split over several calls.  For example, get(4), get(3), and then
  66  * put(5), put(2).
  67  */
  68 void coroutine_fn co_put_to_shres(SharedResource *s, uint64_t n);
  69
  70
  71 #endif /* QEMU_CO_SHARED_RESOURCE_H */