fraud_detection: Fix hash-level locking issues

This patch prevent some rare occassions when, due to too-loose locking,
fraud_detection could run into either:

    * SHM memory leaks
    * incorrectly processed counters (corrupt stats)

modules/fraud_detection/frd_hashmap.c

@@ -53,22 +53,13 @@ int init_hash_map(hash_map_t *hm)
 	return 0;
 }
 
-void** get_item (hash_map_t *hm, str key)
+void** get_item (hash_map_t *hm, str key, rw_lock_t **unlock)
 {
 	unsigned int hash = core_hash(&key, NULL, hm->size);
 
-	lock_start_read(hm->buckets[hash].lock);
-	void **find_res = map_find(hm->buckets[hash].items, key);
-	lock_stop_read(hm->buckets[hash].lock);
-	if (find_res) {
-		return find_res;
-	}
-	else {
-		lock_start_write(hm->buckets[hash].lock);
-		find_res = map_get(hm->buckets[hash].items, key);
-		lock_stop_write(hm->buckets[hash].lock);
-		return find_res;
-	}
+	*unlock = hm->buckets[hash].lock;
+	lock_start_write(hm->buckets[hash].lock);
+	return map_get(hm->buckets[hash].items, key);
 }
 
 void free_hash_map(hash_map_t* hm, void (*value_destroy_func)(void *))

modules/fraud_detection/frd_hashmap.h

@@ -43,7 +43,7 @@ typedef struct {
 
 
 int init_hash_map(hash_map_t* hm);
-void** get_item (hash_map_t *hm, str key);
+void** get_item (hash_map_t *hm, str key, rw_lock_t **unlock);
 void free_hash_map(hash_map_t* hm, void (*value_destroy_func)(void *));
 
 #endif

modules/fraud_detection/frd_stats.c

@@ -58,17 +58,21 @@ int init_stats_table(void)
 
 frd_stats_entry_t* get_stats(str user, str prefix, str *shm_user)
 {
+	rw_lock_t *item_lock;
+
 	/* First go one level below using the user key */
 	frd_users_map_item_t **hm =
-		(frd_users_map_item_t **)get_item(&stats_table, user);
+		(frd_users_map_item_t **)get_item(&stats_table, user, &item_lock);
 
 	if (*hm == NULL) {
 		/* First time the user is seen, we must create a hashmap */
 		*hm = shm_malloc(sizeof(frd_users_map_item_t));
 		if (*hm == NULL) {
+			lock_stop_write(item_lock);
 			LM_ERR("no more shm memory\n");
 			return NULL;
 		}
+		lock_stop_write(item_lock);
 
 		(*hm)->numbers_hm.size = FRD_PREFIX_HASH_SIZE;
 		if (init_hash_map(&(*hm)->numbers_hm) != 0) {
@@ -83,19 +87,23 @@ frd_stats_entry_t* get_stats(str user, str prefix, str *shm_user)
 			return NULL;
 		}
 	}
+	lock_stop_write(item_lock);
 
 	if (shm_user)
 		*shm_user = (*hm)->user;
 
 	frd_stats_entry_t **stats_entry =
-		(frd_stats_entry_t**)get_item(&(*hm)->numbers_hm, prefix);
+		(frd_stats_entry_t**)get_item(&(*hm)->numbers_hm, prefix, &item_lock);
+
 	if (*stats_entry == NULL) {
 		/* First time the prefix is seen for this user */
 		*stats_entry = shm_malloc(sizeof(frd_stats_entry_t));
 		if (*stats_entry == NULL) {
+			lock_stop_write(item_lock);
 			LM_ERR("no more shm memory\n");
 			return NULL;
 		}
+		lock_stop_write(item_lock);
 
 		/* Now init the auxiliary info for a stats structure */
 		if (!lock_init(&(*stats_entry)->lock)) {
@@ -105,24 +113,34 @@ frd_stats_entry_t* get_stats(str user, str prefix, str *shm_user)
 		}
 		memset(&((*stats_entry)->stats), 0, sizeof(frd_stats_t));
 	}
+	lock_stop_write(item_lock);
 
 	return *stats_entry;
 }
 
 
 int stats_exist(str user, str prefix)
 {
+	rw_lock_t *item_lock;
+
 	/* First go one level below using the user key */
 	frd_users_map_item_t **hm =
-		(frd_users_map_item_t **)get_item(&stats_table, user);
+		(frd_users_map_item_t **)get_item(&stats_table, user, &item_lock);
 
-	if (*hm == NULL)
+	if (*hm == NULL) {
+		lock_stop_write(item_lock);
 		return 0;
+	}
+	lock_stop_write(item_lock);
 
 	frd_stats_entry_t **stats_entry =
-		(frd_stats_entry_t**)get_item(&(*hm)->numbers_hm, prefix);
-	if (*stats_entry == NULL)
+		(frd_stats_entry_t**)get_item(&(*hm)->numbers_hm, prefix, &item_lock);
+
+	if (*stats_entry == NULL) {
+		lock_stop_write(item_lock);
 		return 0;
+	}
+	lock_stop_write(item_lock);
 
 	return 1;
 }