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cache: Fix deadlock

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Do not try to adquire the same node lock twice when the cuckoo hashing
resolves to the same node.
This commit is contained in:
Vicent Marti 2011-05-17 00:51:52 +03:00
parent 1e70b96e66
commit 3de79280e3
1 changed files with 14 additions and 6 deletions
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20
src/cache.c
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@ -110,7 +110,7 @@ void *git_cache_try_store(git_cache *cache, void *entry)
cache_node *nodes[GIT_CACHE_OPENADR], *lru_node; cache_node *nodes[GIT_CACHE_OPENADR], *lru_node;
const uint32_t *hash; const uint32_t *hash;
const git_oid *oid; const git_oid *oid;
size_t i; size_t i, j, node_count;
oid = &((git_cached_obj*)entry)->oid; oid = &((git_cached_obj*)entry)->oid;
hash = (const uint32_t *)oid->id; hash = (const uint32_t *)oid->id;
@ -119,16 +119,24 @@ void *git_cache_try_store(git_cache *cache, void *entry)
* the cache now owns it */ * the cache now owns it */
git_cached_obj_incref(entry); git_cached_obj_incref(entry);
node_count = 0;
for (i = 0; i < GIT_CACHE_OPENADR; ++i) { for (i = 0; i < GIT_CACHE_OPENADR; ++i) {
size_t pos = hash[i] & cache->size_mask; size_t pos = hash[i] & cache->size_mask;
cache_node *node = &cache->nodes[pos];
nodes[i] = &cache->nodes[pos]; for (j = 0; j < node_count; ++j)
git_mutex_lock(&nodes[i]->lock); if (nodes[j] == node)
break;
if (j == node_count) {
nodes[node_count++] = node;
git_mutex_lock(node);
}
} }
lru_node = nodes[0]; lru_node = nodes[0];
for (i = 0; i < GIT_CACHE_OPENADR; ++i) { for (i = 0; i < node_count; ++i) {
if (nodes[i]->ptr == NULL) { if (nodes[i]->ptr == NULL) {
nodes[i]->ptr = entry; nodes[i]->ptr = entry;
@ -145,7 +153,7 @@ void *git_cache_try_store(git_cache *cache, void *entry)
lru_node = nodes[i]; lru_node = nodes[i];
} }
if (i == GIT_CACHE_OPENADR) { if (i == node_count) {
void *old_entry = lru_node->ptr; void *old_entry = lru_node->ptr;
assert(old_entry); assert(old_entry);
@ -158,7 +166,7 @@ void *git_cache_try_store(git_cache *cache, void *entry)
* returning it to the user */ * returning it to the user */
git_cached_obj_incref(entry); git_cached_obj_incref(entry);
for (i = 0; i < GIT_CACHE_OPENADR; ++i) for (i = 0; i < node_count; ++i)
git_mutex_unlock(&nodes[i]->lock); git_mutex_unlock(&nodes[i]->lock);
return entry; return entry;