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Fix chunk_recycle() to stop leaking trailing chunks.

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Fix chunk_recycle() to correctly compute trailsize and re-insert
trailing chunks.  This fixes a major virtual memory leak.

Simplify chunk_record() to avoid dropping/re-acquiring chunks_mtx.
This commit is contained in:
Jason Evans 2012-05-09 14:48:35 -07:00
parent de6fbdb72c
commit 374d26a43b
1 changed files with 38 additions and 40 deletions
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52
src/chunk.c
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@ -68,8 +68,8 @@ chunk_recycle(size_t size, size_t alignment, bool base, bool *zero)
}
leadsize = ALIGNMENT_CEILING((uintptr_t)node->addr, alignment) -
(uintptr_t)node->addr;
assert(alloc_size >= leadsize + size);
trailsize = alloc_size - leadsize - size;
assert(node->size >= leadsize + size);
trailsize = node->size - leadsize - size;
ret = (void *)((uintptr_t)node->addr + leadsize);
/* Remove node from the tree. */
extent_tree_szad_remove(&chunks_szad, node);
@ -195,50 +195,48 @@ chunk_record(void *chunk, size_t size)
pages_purge(chunk, size);
xnode = NULL;
/*
* Allocate a node before acquiring chunks_mtx even though it might not
* be needed, because base_node_alloc() may cause a new base chunk to
* be allocated, which could cause deadlock if chunks_mtx were already
* held.
*/
xnode = base_node_alloc();
malloc_mutex_lock(&chunks_mtx);
while (true) {
key.addr = (void *)((uintptr_t)chunk + size);
node = extent_tree_ad_nsearch(&chunks_ad, &key);
/* Try to coalesce forward. */
if (node != NULL && node->addr == key.addr) {
/*
* Coalesce chunk with the following address range.
* This does not change the position within chunks_ad,
* so only remove/insert from/into chunks_szad.
* Coalesce chunk with the following address range. This does
* not change the position within chunks_ad, so only
* remove/insert from/into chunks_szad.
*/
extent_tree_szad_remove(&chunks_szad, node);
node->addr = chunk;
node->size += size;
extent_tree_szad_insert(&chunks_szad, node);
break;
} else if (xnode == NULL) {
/*
* It is possible that base_node_alloc() will cause a
* new base chunk to be allocated, so take care not to
* deadlock on chunks_mtx, and recover if another thread
* deallocates an adjacent chunk while this one is busy
* allocating xnode.
*/
malloc_mutex_unlock(&chunks_mtx);
xnode = base_node_alloc();
if (xnode == NULL)
return;
malloc_mutex_lock(&chunks_mtx);
if (xnode != NULL)
base_node_dealloc(xnode);
} else {
/* Coalescing forward failed, so insert a new node. */
if (xnode == NULL) {
/*
* base_node_alloc() failed, which is an exceedingly
* unlikely failure. Leak chunk; its pages have
* already been purged, so this is only a virtual
* memory leak.
*/
malloc_mutex_unlock(&chunks_mtx);
return;
}
node = xnode;
xnode = NULL;
node->addr = chunk;
node->size = size;
extent_tree_ad_insert(&chunks_ad, node);
extent_tree_szad_insert(&chunks_szad, node);
break;
}
}
/* Discard xnode if it ended up unused due to a race. */
if (xnode != NULL)
base_node_dealloc(xnode);
/* Try to coalesce backward. */
prev = extent_tree_ad_prev(&chunks_ad, node);