src/common/index-allocator.cpp

   1 /*
   2  * Copyright (C) 2020 Francis Deslauriers <francis.deslauriers@efficios.com>
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-only
   5  *
   6  */
   7
   8 #include <inttypes.h>
   9
  10 #include <urcu.h>
  11 #include <urcu/list.h>
  12
  13 #include "macros.hpp"
  14 #include "error.hpp"
  15
  16 #include "index-allocator.hpp"
  17
  18 struct lttng_index_allocator {
  19         struct cds_list_head unused_list;
  20         uint64_t size;
  21         uint64_t position;
  22         uint64_t nb_allocated_indexes;
  23 };
  24
  25 namespace {
  26 struct lttng_index {
  27         uint64_t index;
  28         struct cds_list_head head;
  29 };
  30 } /* namespace */
  31
  32 struct lttng_index_allocator *lttng_index_allocator_create(
  33                 uint64_t index_count)
  34 {
  35         struct lttng_index_allocator *allocator = NULL;
  36
  37         allocator = zmalloc<lttng_index_allocator>();
  38         if (!allocator) {
  39                 PERROR("Failed to allocate index allocator");
  40                 goto end;
  41         }
  42
  43         allocator->size = index_count;
  44         allocator->position = 0;
  45         allocator->nb_allocated_indexes = 0;
  46
  47         CDS_INIT_LIST_HEAD(&allocator->unused_list);
  48
  49 end:
  50         return allocator;
  51 }
  52
  53 uint64_t lttng_index_allocator_get_index_count(struct lttng_index_allocator *allocator)
  54 {
  55         return allocator->nb_allocated_indexes;
  56 }
  57
  58 enum lttng_index_allocator_status lttng_index_allocator_alloc(
  59                 struct lttng_index_allocator *allocator,
  60                 uint64_t *allocated_index)
  61 {
  62         enum lttng_index_allocator_status status =
  63                         LTTNG_INDEX_ALLOCATOR_STATUS_OK;
  64
  65         if (cds_list_empty(&allocator->unused_list)) {
  66                 if (allocator->position >= allocator->size) {
  67                         /* No indices left. */
  68                         status = LTTNG_INDEX_ALLOCATOR_STATUS_EMPTY;
  69                         goto end;
  70                 }
  71
  72                 *allocated_index = allocator->position++;
  73         } else {
  74                 struct lttng_index *index;
  75
  76                 index = cds_list_first_entry(&allocator->unused_list,
  77                                 typeof(*index), head);
  78                 cds_list_del(&index->head);
  79                 *allocated_index = index->index;
  80                 free(index);
  81         }
  82
  83         allocator->nb_allocated_indexes++;
  84 end:
  85         return status;
  86 }
  87
  88 enum lttng_index_allocator_status lttng_index_allocator_release(
  89                 struct lttng_index_allocator *allocator, uint64_t idx)
  90 {
  91         struct lttng_index *index = NULL;
  92         enum lttng_index_allocator_status status =
  93                         LTTNG_INDEX_ALLOCATOR_STATUS_OK;
  94
  95         LTTNG_ASSERT(idx < allocator->size);
  96
  97         index = zmalloc<lttng_index>();
  98         if (!index) {
  99                 PERROR("Failed to allocate free index queue");
 100                 status = LTTNG_INDEX_ALLOCATOR_STATUS_ERROR;
 101                 goto end;
 102         }
 103
 104         index->index = idx;
 105         cds_list_add_tail(&index->head, &allocator->unused_list);
 106         allocator->nb_allocated_indexes--;
 107
 108 end:
 109         return status;
 110 }
 111
 112 void lttng_index_allocator_destroy(struct lttng_index_allocator *allocator)
 113 {
 114         struct lttng_index *index = NULL, *tmp_index = NULL;
 115
 116         if (!allocator) {
 117                 return;
 118         }
 119
 120         if (lttng_index_allocator_get_index_count(allocator) > 0) {
 121                 WARN("Destroying index allocator with %" PRIu64
 122                                 " slot indexes still in use",
 123                                 lttng_index_allocator_get_index_count(allocator));
 124         }
 125
 126         cds_list_for_each_entry_safe(index, tmp_index,
 127                         &allocator->unused_list, head) {
 128                 cds_list_del(&index->head);
 129                 free(index);
 130         }
 131
 132         free(allocator);
 133 }