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