1 /* Free a block of memory allocated by `mmalloc'. */
3 /* Copyright (c) 2010-2022. The SimGrid Team. All rights reserved. */
5 /* This program is free software; you can redistribute it and/or modify it
6 * under the terms of the license (GNU LGPL) which comes with this package. */
8 /* Copyright 1990, 1991, 1992 Free Software Foundation
10 Written May 1989 by Mike Haertel.
11 Heavily modified Mar 1992 by Fred Fish. (fnf@cygnus.com) */
13 #include "mmprivate.h"
16 /* Return memory to the heap.
17 Like `mfree' but don't call a mfree_hook if there is one. */
19 /* Return memory to the heap. */
20 void mfree(struct mdesc *mdp, void *ptr)
29 size_t block = BLOCK(ptr);
31 if ((char *) ptr < (char *) mdp->heapbase || block > mdp->heapsize) {
32 fprintf(stderr,"Ouch, this pointer is not mine, I refuse to free it. Give me valid pointers, or give me death!!\n");
36 int type = mdp->heapinfo[block].type;
39 case MMALLOC_TYPE_HEAPINFO:
41 fprintf(stderr, "Asked to free a fragment in a heapinfo block. I'm confused.\n");
45 case MMALLOC_TYPE_FREE: /* Already free */
47 fprintf(stderr, "Asked to free a fragment in a block that is already free. I'm puzzled.\n");
51 case MMALLOC_TYPE_UNFRAGMENTED:
52 /* Get as many statistics as early as we can. */
53 mdp -> heapstats.chunks_used--;
54 mdp -> heapstats.bytes_used -=
55 mdp -> heapinfo[block].busy_block.size * BLOCKSIZE;
56 mdp -> heapstats.bytes_free +=
57 mdp -> heapinfo[block].busy_block.size * BLOCKSIZE;
59 if (MC_is_active() && mdp->heapinfo[block].busy_block.ignore > 0)
60 MC_unignore_heap(ptr, mdp->heapinfo[block].busy_block.busy_size);
62 /* Find the free cluster previous to this one in the free list.
63 Start searching at the last block referenced; this may benefit
64 programs with locality of allocation. */
68 i = mdp->heapinfo[i].free_block.prev;
72 i = mdp->heapinfo[i].free_block.next;
74 while ((i != 0) && (i < block));
75 i = mdp->heapinfo[i].free_block.prev;
78 /* Determine how to link this block into the free list. */
79 if (block == i + mdp->heapinfo[i].free_block.size) {
81 /* Coalesce this block with its predecessor. */
82 mdp->heapinfo[i].free_block.size += mdp->heapinfo[block].busy_block.size;
83 /* Mark all my ex-blocks as free */
84 for (it=0; it<mdp->heapinfo[block].busy_block.size; it++) {
85 if (mdp->heapinfo[block+it].type < 0) {
87 "Internal Error: Asked to free a block already marked as free (block=%zu it=%d type=%d). "
88 "Please report this bug.\n",
89 block, it, mdp->heapinfo[block].type);
92 mdp->heapinfo[block+it].type = MMALLOC_TYPE_FREE;
97 /* Really link this block back into the free list. */
98 mdp->heapinfo[block].free_block.size = mdp->heapinfo[block].busy_block.size;
99 mdp->heapinfo[block].free_block.next = mdp->heapinfo[i].free_block.next;
100 mdp->heapinfo[block].free_block.prev = i;
101 mdp->heapinfo[i].free_block.next = block;
102 mdp->heapinfo[mdp->heapinfo[block].free_block.next].free_block.prev = block;
103 mdp -> heapstats.chunks_free++;
104 /* Mark all my ex-blocks as free */
105 for (it=0; it<mdp->heapinfo[block].free_block.size; it++) {
106 if (mdp->heapinfo[block+it].type <0) {
108 "Internal error: Asked to free a block already marked as free (block=%zu it=%d/%zu type=%d). "
109 "Please report this bug.\n",
110 block, it, mdp->heapinfo[block].free_block.size, mdp->heapinfo[block].type);
113 mdp->heapinfo[block+it].type = MMALLOC_TYPE_FREE;
117 /* Now that the block is linked in, see if we can coalesce it
118 with its successor (by deleting its successor from the list
119 and adding in its size). */
120 if (block + mdp->heapinfo[block].free_block.size ==
121 mdp->heapinfo[block].free_block.next) {
122 mdp->heapinfo[block].free_block.size
123 += mdp->heapinfo[mdp->heapinfo[block].free_block.next].free_block.size;
124 mdp->heapinfo[block].free_block.next
125 = mdp->heapinfo[mdp->heapinfo[block].free_block.next].free_block.next;
126 mdp->heapinfo[mdp->heapinfo[block].free_block.next].free_block.prev = block;
127 mdp -> heapstats.chunks_free--;
130 /* Now see if we can return stuff to the system. */
132 blocks = mdp -> heapinfo[block].free.size;
133 if (blocks >= FINAL_FREE_BLOCKS && block + blocks == mdp -> heaplimit
134 && mdp -> morecore (mdp, 0) == ADDRESS (block + blocks))
136 register size_t bytes = blocks * BLOCKSIZE;
137 mdp -> heaplimit -= blocks;
138 mdp -> morecore (mdp, -bytes);
139 mdp -> heapinfo[mdp -> heapinfo[block].free.prev].free.next
140 = mdp -> heapinfo[block].free.next;
141 mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.prev
142 = mdp -> heapinfo[block].free.prev;
143 block = mdp -> heapinfo[block].free.prev;
144 mdp -> heapstats.chunks_free--;
145 mdp -> heapstats.bytes_free -= bytes;
149 /* Set the next search to begin at this block.
150 This is probably important to the trick where realloc returns the block to
151 the system before reasking for the same block with a bigger size. */
152 mdp->heapindex = block;
157 fprintf(stderr, "Unknown mmalloc block type.\n");
161 /* Do some of the statistics. */
162 mdp -> heapstats.chunks_used--;
163 mdp -> heapstats.bytes_used -= 1 << type;
164 mdp -> heapstats.chunks_free++;
165 mdp -> heapstats.bytes_free += 1 << type;
167 frag_nb = RESIDUAL(ptr, BLOCKSIZE) >> type;
169 if( mdp->heapinfo[block].busy_frag.frag_size[frag_nb] == -1){
171 fprintf(stderr, "Asked to free a fragment that is already free. I'm puzzled\n");
175 if (MC_is_active() && mdp->heapinfo[block].busy_frag.ignore[frag_nb] > 0)
176 MC_unignore_heap(ptr, mdp->heapinfo[block].busy_frag.frag_size[frag_nb]);
178 /* Set size used in the fragment to -1 */
179 mdp->heapinfo[block].busy_frag.frag_size[frag_nb] = -1;
180 mdp->heapinfo[block].busy_frag.ignore[frag_nb] = 0;
182 if (mdp->heapinfo[block].busy_frag.nfree ==
183 (BLOCKSIZE >> type) - 1) {
184 /* If all fragments of this block are free, remove this block from its swag and free the whole block. */
185 xbt_swag_remove(&mdp->heapinfo[block],&mdp->fraghead[type]);
187 /* pretend that this block is used and free it so that it gets properly coalesced with adjacent free blocks */
188 mdp->heapinfo[block].type = MMALLOC_TYPE_UNFRAGMENTED;
189 mdp->heapinfo[block].busy_block.size = 1;
190 mdp->heapinfo[block].busy_block.busy_size = 0;
192 /* Keep the statistics accurate. */
193 mdp -> heapstats.chunks_used++;
194 mdp -> heapstats.bytes_used += BLOCKSIZE;
195 mdp -> heapstats.chunks_free -= BLOCKSIZE >> type;
196 mdp -> heapstats.bytes_free -= BLOCKSIZE;
198 mfree(mdp, ADDRESS(block));
199 } else if (mdp->heapinfo[block].busy_frag.nfree != 0) {
200 /* If some fragments of this block are free, you know what? I'm already happy. */
201 ++mdp->heapinfo[block].busy_frag.nfree;
203 /* No fragments of this block were free before the one we just released,
204 * so add this block to the swag and announce that
205 it is the first free fragment of this block. */
206 mdp->heapinfo[block].busy_frag.nfree = 1;
207 mdp->heapinfo[block].freehook.prev = NULL;
208 mdp->heapinfo[block].freehook.next = NULL;
210 xbt_swag_insert(&mdp->heapinfo[block],&mdp->fraghead[type]);