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b4e8d170 | 1 | /* Copyright (c) 2011, 2012 Nicira, Inc. |
e317253b BP |
2 | * |
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: | |
6 | * | |
7 | * http://www.apache.org/licenses/LICENSE-2.0 | |
8 | * | |
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. | |
14 | */ | |
15 | ||
16 | #include <config.h> | |
17 | ||
18 | #include "server.h" | |
19 | ||
da897f41 | 20 | #include "hash.h" |
b4e8d170 | 21 | #include "ovsdb.h" |
da897f41 | 22 | |
b4e8d170 | 23 | /* Initializes 'session' as a session within 'server'. */ |
e317253b | 24 | void |
b4e8d170 | 25 | ovsdb_session_init(struct ovsdb_session *session, struct ovsdb_server *server) |
e317253b | 26 | { |
b4e8d170 | 27 | session->server = server; |
e317253b | 28 | list_init(&session->completions); |
da897f41 | 29 | hmap_init(&session->waiters); |
e317253b BP |
30 | } |
31 | ||
32 | /* Destroys 'session'. */ | |
33 | void | |
da897f41 BP |
34 | ovsdb_session_destroy(struct ovsdb_session *session) |
35 | { | |
cb22974d | 36 | ovs_assert(hmap_is_empty(&session->waiters)); |
da897f41 BP |
37 | hmap_destroy(&session->waiters); |
38 | } | |
39 | ||
40 | /* Searches 'session' for an ovsdb_lock_waiter named 'lock_name' and returns | |
41 | * it if it finds one, otherwise NULL. */ | |
42 | struct ovsdb_lock_waiter * | |
43 | ovsdb_session_get_lock_waiter(const struct ovsdb_session *session, | |
44 | const char *lock_name) | |
45 | { | |
46 | struct ovsdb_lock_waiter *waiter; | |
47 | ||
48 | HMAP_FOR_EACH_WITH_HASH (waiter, session_node, hash_string(lock_name, 0), | |
49 | &session->waiters) { | |
50 | if (!strcmp(lock_name, waiter->lock_name)) { | |
51 | return waiter; | |
52 | } | |
53 | } | |
54 | return NULL; | |
55 | } | |
56 | ||
57 | /* Returns the waiter that owns 'lock'. | |
58 | * | |
59 | * A lock always has an owner, so this function will never return NULL. */ | |
60 | struct ovsdb_lock_waiter * | |
61 | ovsdb_lock_get_owner(const struct ovsdb_lock *lock) | |
62 | { | |
63 | return CONTAINER_OF(list_front(&lock->waiters), | |
64 | struct ovsdb_lock_waiter, lock_node); | |
65 | } | |
66 | ||
67 | /* Removes 'waiter' from its lock's list. This means that, if 'waiter' was | |
68 | * formerly the owner of its lock, then it no longer owns it. | |
69 | * | |
70 | * Returns the session that now owns 'waiter'. This is NULL if 'waiter' was | |
71 | * the lock's owner and no other sessions were waiting for the lock. In this | |
72 | * case, the lock has been destroyed, so the caller must be sure not to refer | |
73 | * to it again. A nonnull return value reflects a change in the lock's | |
74 | * ownership if and only if 'waiter' formerly owned the lock. */ | |
75 | struct ovsdb_session * | |
76 | ovsdb_lock_waiter_remove(struct ovsdb_lock_waiter *waiter) | |
77 | { | |
78 | struct ovsdb_lock *lock = waiter->lock; | |
79 | ||
80 | list_remove(&waiter->lock_node); | |
81 | waiter->lock = NULL; | |
82 | ||
83 | if (list_is_empty(&lock->waiters)) { | |
84 | hmap_remove(&lock->server->locks, &lock->hmap_node); | |
85 | free(lock->name); | |
86 | free(lock); | |
87 | return NULL; | |
88 | } | |
89 | ||
90 | return ovsdb_lock_get_owner(lock)->session; | |
91 | } | |
92 | ||
93 | /* Destroys 'waiter', which must have already been removed from its lock's | |
94 | * waiting list with ovsdb_lock_waiter_remove(). | |
95 | * | |
96 | * Removing and destroying locks are decoupled because a lock initially created | |
97 | * by the "steal" request, that is later stolen by another client, remains in | |
98 | * the database session until the database client sends an "unlock" request. */ | |
99 | void | |
100 | ovsdb_lock_waiter_destroy(struct ovsdb_lock_waiter *waiter) | |
101 | { | |
cb22974d | 102 | ovs_assert(!waiter->lock); |
da897f41 BP |
103 | hmap_remove(&waiter->session->waiters, &waiter->session_node); |
104 | free(waiter->lock_name); | |
105 | free(waiter); | |
106 | } | |
107 | ||
108 | /* Returns true if 'waiter' owns its associated lock. */ | |
109 | bool | |
110 | ovsdb_lock_waiter_is_owner(const struct ovsdb_lock_waiter *waiter) | |
e317253b | 111 | { |
da897f41 | 112 | return waiter->lock && waiter == ovsdb_lock_get_owner(waiter->lock); |
e317253b BP |
113 | } |
114 | ||
b4e8d170 BP |
115 | /* Initializes 'server'. |
116 | * | |
117 | * The caller must call ovsdb_server_add_db() for each database to which | |
118 | * 'server' should provide access. */ | |
e317253b | 119 | void |
b4e8d170 | 120 | ovsdb_server_init(struct ovsdb_server *server) |
e317253b | 121 | { |
b4e8d170 | 122 | shash_init(&server->dbs); |
da897f41 | 123 | hmap_init(&server->locks); |
e317253b BP |
124 | } |
125 | ||
b4e8d170 BP |
126 | /* Adds 'db' to the set of databases served out by 'server'. Returns true if |
127 | * successful, false if 'db''s name is the same as some database already in | |
128 | * 'server'. */ | |
129 | bool | |
130 | ovsdb_server_add_db(struct ovsdb_server *server, struct ovsdb *db) | |
131 | { | |
132 | return shash_add_once(&server->dbs, db->schema->name, db); | |
133 | } | |
134 | ||
e317253b BP |
135 | /* Destroys 'server'. */ |
136 | void | |
da897f41 BP |
137 | ovsdb_server_destroy(struct ovsdb_server *server) |
138 | { | |
b4e8d170 | 139 | shash_destroy(&server->dbs); |
da897f41 BP |
140 | hmap_destroy(&server->locks); |
141 | } | |
142 | ||
143 | static struct ovsdb_lock * | |
144 | ovsdb_server_create_lock__(struct ovsdb_server *server, const char *lock_name, | |
145 | uint32_t hash) | |
146 | { | |
147 | struct ovsdb_lock *lock; | |
148 | ||
149 | HMAP_FOR_EACH_WITH_HASH (lock, hmap_node, hash, &server->locks) { | |
150 | if (!strcmp(lock->name, lock_name)) { | |
151 | return lock; | |
152 | } | |
153 | } | |
154 | ||
155 | lock = xzalloc(sizeof *lock); | |
156 | lock->server = server; | |
157 | lock->name = xstrdup(lock_name); | |
158 | hmap_insert(&server->locks, &lock->hmap_node, hash); | |
159 | list_init(&lock->waiters); | |
160 | ||
161 | return lock; | |
162 | } | |
163 | ||
164 | /* Attempts to acquire the lock named 'lock_name' for 'session' within | |
165 | * 'server'. Returns the new lock waiter. | |
166 | * | |
167 | * If 'mode' is OVSDB_LOCK_STEAL, then the new lock waiter is always the owner | |
168 | * of the lock. '*victimp' receives the session of the previous owner or NULL | |
169 | * if the lock was previously unowned. (If the victim itself originally | |
170 | * obtained the lock through a "steal" operation, then this function also | |
171 | * removes the victim from the lock's waiting list.) | |
172 | * | |
173 | * If 'mode' is OVSDB_LOCK_WAIT, then the new lock waiter is the owner of the | |
174 | * lock only if this lock had no existing owner. '*victimp' is set to NULL. */ | |
175 | struct ovsdb_lock_waiter * | |
176 | ovsdb_server_lock(struct ovsdb_server *server, | |
177 | struct ovsdb_session *session, | |
178 | const char *lock_name, | |
179 | enum ovsdb_lock_mode mode, | |
180 | struct ovsdb_session **victimp) | |
e317253b | 181 | { |
da897f41 BP |
182 | uint32_t hash = hash_string(lock_name, 0); |
183 | struct ovsdb_lock_waiter *waiter, *victim; | |
184 | struct ovsdb_lock *lock; | |
185 | ||
186 | lock = ovsdb_server_create_lock__(server, lock_name, hash); | |
187 | victim = (mode == OVSDB_LOCK_STEAL && !list_is_empty(&lock->waiters) | |
188 | ? ovsdb_lock_get_owner(lock) | |
189 | : NULL); | |
190 | ||
191 | waiter = xmalloc(sizeof *waiter); | |
192 | waiter->mode = mode; | |
193 | waiter->lock_name = xstrdup(lock_name); | |
194 | waiter->lock = lock; | |
195 | if (mode == OVSDB_LOCK_STEAL) { | |
196 | list_push_front(&lock->waiters, &waiter->lock_node); | |
197 | } else { | |
198 | list_push_back(&lock->waiters, &waiter->lock_node); | |
199 | } | |
200 | waiter->session = session; | |
201 | hmap_insert(&waiter->session->waiters, &waiter->session_node, hash); | |
202 | ||
203 | if (victim && victim->mode == OVSDB_LOCK_STEAL) { | |
204 | ovsdb_lock_waiter_remove(victim); | |
205 | } | |
206 | *victimp = victim ? victim->session : NULL; | |
207 | ||
208 | return waiter; | |
e317253b | 209 | } |