1 /* Copyright (c) 2011, 2012 Nicira, Inc.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at:
7 * http://www.apache.org/licenses/LICENSE-2.0
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
25 /* Initializes 'session' as a session within 'server'. */
27 ovsdb_session_init(struct ovsdb_session *session, struct ovsdb_server *server)
29 session->server = server;
30 list_init(&session->completions);
31 hmap_init(&session->waiters);
34 /* Destroys 'session'. */
36 ovsdb_session_destroy(struct ovsdb_session *session)
38 assert(hmap_is_empty(&session->waiters));
39 hmap_destroy(&session->waiters);
42 /* Searches 'session' for an ovsdb_lock_waiter named 'lock_name' and returns
43 * it if it finds one, otherwise NULL. */
44 struct ovsdb_lock_waiter *
45 ovsdb_session_get_lock_waiter(const struct ovsdb_session *session,
46 const char *lock_name)
48 struct ovsdb_lock_waiter *waiter;
50 HMAP_FOR_EACH_WITH_HASH (waiter, session_node, hash_string(lock_name, 0),
52 if (!strcmp(lock_name, waiter->lock_name)) {
59 /* Returns the waiter that owns 'lock'.
61 * A lock always has an owner, so this function will never return NULL. */
62 struct ovsdb_lock_waiter *
63 ovsdb_lock_get_owner(const struct ovsdb_lock *lock)
65 return CONTAINER_OF(list_front(&lock->waiters),
66 struct ovsdb_lock_waiter, lock_node);
69 /* Removes 'waiter' from its lock's list. This means that, if 'waiter' was
70 * formerly the owner of its lock, then it no longer owns it.
72 * Returns the session that now owns 'waiter'. This is NULL if 'waiter' was
73 * the lock's owner and no other sessions were waiting for the lock. In this
74 * case, the lock has been destroyed, so the caller must be sure not to refer
75 * to it again. A nonnull return value reflects a change in the lock's
76 * ownership if and only if 'waiter' formerly owned the lock. */
77 struct ovsdb_session *
78 ovsdb_lock_waiter_remove(struct ovsdb_lock_waiter *waiter)
80 struct ovsdb_lock *lock = waiter->lock;
82 list_remove(&waiter->lock_node);
85 if (list_is_empty(&lock->waiters)) {
86 hmap_remove(&lock->server->locks, &lock->hmap_node);
92 return ovsdb_lock_get_owner(lock)->session;
95 /* Destroys 'waiter', which must have already been removed from its lock's
96 * waiting list with ovsdb_lock_waiter_remove().
98 * Removing and destroying locks are decoupled because a lock initially created
99 * by the "steal" request, that is later stolen by another client, remains in
100 * the database session until the database client sends an "unlock" request. */
102 ovsdb_lock_waiter_destroy(struct ovsdb_lock_waiter *waiter)
104 assert(!waiter->lock);
105 hmap_remove(&waiter->session->waiters, &waiter->session_node);
106 free(waiter->lock_name);
110 /* Returns true if 'waiter' owns its associated lock. */
112 ovsdb_lock_waiter_is_owner(const struct ovsdb_lock_waiter *waiter)
114 return waiter->lock && waiter == ovsdb_lock_get_owner(waiter->lock);
117 /* Initializes 'server'.
119 * The caller must call ovsdb_server_add_db() for each database to which
120 * 'server' should provide access. */
122 ovsdb_server_init(struct ovsdb_server *server)
124 shash_init(&server->dbs);
125 hmap_init(&server->locks);
128 /* Adds 'db' to the set of databases served out by 'server'. Returns true if
129 * successful, false if 'db''s name is the same as some database already in
132 ovsdb_server_add_db(struct ovsdb_server *server, struct ovsdb *db)
134 return shash_add_once(&server->dbs, db->schema->name, db);
137 /* Destroys 'server'. */
139 ovsdb_server_destroy(struct ovsdb_server *server)
141 shash_destroy(&server->dbs);
142 hmap_destroy(&server->locks);
145 static struct ovsdb_lock *
146 ovsdb_server_create_lock__(struct ovsdb_server *server, const char *lock_name,
149 struct ovsdb_lock *lock;
151 HMAP_FOR_EACH_WITH_HASH (lock, hmap_node, hash, &server->locks) {
152 if (!strcmp(lock->name, lock_name)) {
157 lock = xzalloc(sizeof *lock);
158 lock->server = server;
159 lock->name = xstrdup(lock_name);
160 hmap_insert(&server->locks, &lock->hmap_node, hash);
161 list_init(&lock->waiters);
166 /* Attempts to acquire the lock named 'lock_name' for 'session' within
167 * 'server'. Returns the new lock waiter.
169 * If 'mode' is OVSDB_LOCK_STEAL, then the new lock waiter is always the owner
170 * of the lock. '*victimp' receives the session of the previous owner or NULL
171 * if the lock was previously unowned. (If the victim itself originally
172 * obtained the lock through a "steal" operation, then this function also
173 * removes the victim from the lock's waiting list.)
175 * If 'mode' is OVSDB_LOCK_WAIT, then the new lock waiter is the owner of the
176 * lock only if this lock had no existing owner. '*victimp' is set to NULL. */
177 struct ovsdb_lock_waiter *
178 ovsdb_server_lock(struct ovsdb_server *server,
179 struct ovsdb_session *session,
180 const char *lock_name,
181 enum ovsdb_lock_mode mode,
182 struct ovsdb_session **victimp)
184 uint32_t hash = hash_string(lock_name, 0);
185 struct ovsdb_lock_waiter *waiter, *victim;
186 struct ovsdb_lock *lock;
188 lock = ovsdb_server_create_lock__(server, lock_name, hash);
189 victim = (mode == OVSDB_LOCK_STEAL && !list_is_empty(&lock->waiters)
190 ? ovsdb_lock_get_owner(lock)
193 waiter = xmalloc(sizeof *waiter);
195 waiter->lock_name = xstrdup(lock_name);
197 if (mode == OVSDB_LOCK_STEAL) {
198 list_push_front(&lock->waiters, &waiter->lock_node);
200 list_push_back(&lock->waiters, &waiter->lock_node);
202 waiter->session = session;
203 hmap_insert(&waiter->session->waiters, &waiter->session_node, hash);
205 if (victim && victim->mode == OVSDB_LOCK_STEAL) {
206 ovsdb_lock_waiter_remove(victim);
208 *victimp = victim ? victim->session : NULL;