lock: Add named lock capability

Locking some objects like sorcery objects can be tricky because the underlying
ao2 object may not be the same for all callers.  For instance, two threads that
call ast_sorcery_retrieve_by_id on the same aor name might actually get 2
different ao2 objects if the underlying wizard had to rehydrate the aor from a
database. Locking one ao2 object doesn't have any effect on the other even if
those objects had locks in the first place.

Named locks allow access control by keyspace and key strings.  Now an "aor"
named "1000" can be locked and any other thread attempting to lock "aor" "1000"
will wait regardless of whether the underlying ao2 object is the same or not.
Mutex and rwlocks are supported.

This capability will initially be used to lock an aor when multiple threads may
be attempting to prune expired contacts from it.

Change-Id: If258c0b7f92b02d07243ce70e535821a1ea7fb45

1 files changed, 142 insertions, 0 deletions

diff --git a/main/named_locks.c b/main/named_locks.c
new file mode 100644
index 000000000..b977b553c
--- /dev/null
+++ b/main/named_locks.c
@@ -0,0 +1,142 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2016, Fairview 5 Engineering, LLC
+ *
+ * George Joseph <george.joseph@fairview5.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+/*! \file
+ *
+ * \brief Named Locks
+ *
+ * \author George Joseph <george.joseph@fairview5.com>
+ */
+
+#include "asterisk.h"
+
+ASTERISK_REGISTER_FILE()
+
+#include "asterisk/_private.h"
+#include "asterisk/astobj2.h"
+#include "asterisk/named_locks.h"
+#include "asterisk/utils.h"
+
+struct ao2_container *named_locks;
+#define NAMED_LOCKS_BUCKETS 101
+
+struct ast_named_lock {
+	char key[0];
+};
+
+static int named_locks_hash(const void *obj, const int flags)
+{
+	const struct ast_named_lock *lock = obj;
+
+	switch (flags & OBJ_SEARCH_MASK) {
+	case OBJ_SEARCH_KEY:
+		return ast_str_hash(obj);
+	case OBJ_SEARCH_OBJECT:
+		return ast_str_hash(lock->key);
+	default:
+		/* Hash can only work on something with a full key. */
+		ast_assert(0);
+		return 0;
+	}
+}
+
+static int named_locks_cmp(void *obj_left, void *obj_right, int flags)
+{
+	const struct ast_named_lock *object_left = obj_left;
+	const struct ast_named_lock *object_right = obj_right;
+	const char *right_key = obj_right;
+	int cmp;
+
+	switch (flags & OBJ_SEARCH_MASK) {
+	case OBJ_SEARCH_OBJECT:
+		right_key = object_right->key;
+		/* Fall through */
+	case OBJ_SEARCH_KEY:
+		cmp = strcmp(object_left->key, right_key);
+		break;
+	case OBJ_SEARCH_PARTIAL_KEY:
+		cmp = strncmp(object_left->key, right_key, strlen(right_key));
+		break;
+	default:
+		cmp = 0;
+		break;
+	}
+
+	return cmp ? 0 : CMP_MATCH;
+}
+
+static void named_locks_shutdown(void)
+{
+	ao2_cleanup(named_locks);
+}
+
+int ast_named_locks_init(void)
+{
+	named_locks = ao2_container_alloc_hash(0, 0, NAMED_LOCKS_BUCKETS, named_locks_hash, NULL,
+		named_locks_cmp);
+	if (!named_locks) {
+		return -1;
+	}
+
+	ast_register_cleanup(named_locks_shutdown);
+
+	return 0;
+}
+
+struct ast_named_lock *__ast_named_lock_get(const char *filename, int lineno, const char *func,
+	enum ast_named_lock_type lock_type, const char *keyspace, const char *key)
+{
+	struct ast_named_lock *lock = NULL;
+	int concat_key_buff_len = strlen(keyspace) + strlen(key) + 2;
+	char *concat_key = ast_alloca(concat_key_buff_len);
+
+	sprintf(concat_key, "%s-%s", keyspace, key); /* Safe */
+
+	ao2_lock(named_locks);
+	lock = ao2_find(named_locks, concat_key, OBJ_SEARCH_KEY | OBJ_NOLOCK);
+	if (lock) {
+		ao2_unlock(named_locks);
+		ast_assert((ao2_options_get(lock) & AO2_ALLOC_OPT_LOCK_MASK) == lock_type);
+		return lock;
+	}
+
+	lock = ao2_alloc_options(sizeof(*lock) + concat_key_buff_len, NULL, lock_type);
+	if (lock) {
+		strcpy(lock->key, concat_key); /* Safe */
+		ao2_link_flags(named_locks, lock, OBJ_NOLOCK);
+	}
+	ao2_unlock(named_locks);
+
+	return lock;
+}
+
+int __ast_named_lock_put(const char *filename, int lineno, const char *func,
+	struct ast_named_lock *lock)
+{
+	if (!lock) {
+		return -1;
+	}
+
+	ao2_lock(named_locks);
+	if (ao2_ref(lock, -1) == 2) {
+		ao2_unlink_flags(named_locks, lock, OBJ_NOLOCK);
+	}
+	ao2_unlock(named_locks);
+
+	return 0;
+}