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Merge "res_sorcery_memory_cache.c: Fix deadlock with scheduler."

This commit is contained in:
Joshua Colp 2015-10-02 16:28:09 -05:00 committed by Gerrit Code Review
parent 45bba81f67 1b80dbeb60
commit ace043f4ea
1 changed files with 22 additions and 13 deletions
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35
res/res_sorcery_memory_cache.c
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@ -124,6 +124,8 @@ struct sorcery_memory_cache {
struct ast_heap *object_heap;
/*! \brief Scheduler item for expiring oldest object. */
int expire_id;
/*! TRUE if trying to stop the oldest object expiration scheduler item. */
unsigned int del_expire:1;
#ifdef TEST_FRAMEWORK
/*! \brief Variable used to indicate we should notify a test when we reach empty */
unsigned int cache_notify;
@ -443,7 +445,21 @@ static int expire_objects_from_cache(const void *data)
struct sorcery_memory_cache *cache = (struct sorcery_memory_cache *)data;
struct sorcery_memory_cached_object *cached;
ao2_wrlock(cache->objects);
/*
* We need to do deadlock avoidance between a non-scheduler thread
* blocking when trying to delete the scheduled entry for this
* callback because the scheduler thread is running this callback
* and this callback waiting for the cache->objects container lock
* that the blocked non-scheduler thread already holds.
*/
while (ao2_trywrlock(cache->objects)) {
if (cache->del_expire) {
cache->expire_id = -1;
ao2_ref(cache, -1);
return 0;
}
sched_yield();
}
cache->expire_id = -1;
@ -488,7 +504,9 @@ static void remove_all_from_cache(struct sorcery_memory_cache *cache)
ao2_callback(cache->objects, OBJ_UNLINK | OBJ_NOLOCK | OBJ_NODATA | OBJ_MULTIPLE,
NULL, NULL);
cache->del_expire = 1;
AST_SCHED_DEL_UNREF(sched, cache->expire_id, ao2_ref(cache, -1));
cache->del_expire = 0;
}
/*!
@ -581,18 +599,9 @@ static int schedule_cache_expiration(struct sorcery_memory_cache *cache)
return 0;
}
if (cache->expire_id != -1) {
/* If we can't unschedule this expiration then it is currently attempting to run,
* so let it run - it just means that it'll be the one scheduling instead of us.
*/
if (ast_sched_del(sched, cache->expire_id)) {
return 0;
}
/* Since it successfully cancelled we need to drop the ref to the cache it had */
ao2_ref(cache, -1);
cache->expire_id = -1;
}
cache->del_expire = 1;
AST_SCHED_DEL_UNREF(sched, cache->expire_id, ao2_ref(cache, -1));
cache->del_expire = 0;
cached = ast_heap_peek(cache->object_heap, 1);
if (!cached) {