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e0edde6f | 1 | /* Copyright (c) 2011 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 BP |
20 | #include <assert.h> |
21 | ||
22 | #include "hash.h" | |
23 | ||
e317253b BP |
24 | /* Initializes 'session' as a session that operates on 'db'. */ |
25 | void | |
26 | ovsdb_session_init(struct ovsdb_session *session, struct ovsdb *db) | |
27 | { | |
28 | session->db = db; | |
29 | list_init(&session->completions); | |
da897f41 | 30 | hmap_init(&session->waiters); |
e317253b BP |
31 | } |
32 | ||
33 | /* Destroys 'session'. */ | |
34 | void | |
da897f41 BP |
35 | ovsdb_session_destroy(struct ovsdb_session *session) |
36 | { | |
37 | assert(hmap_is_empty(&session->waiters)); | |
38 | hmap_destroy(&session->waiters); | |
39 | } | |
40 | ||
41 | /* Searches 'session' for an ovsdb_lock_waiter named 'lock_name' and returns | |
42 | * it if it finds one, otherwise NULL. */ | |
43 | struct ovsdb_lock_waiter * | |
44 | ovsdb_session_get_lock_waiter(const struct ovsdb_session *session, | |
45 | const char *lock_name) | |
46 | { | |
47 | struct ovsdb_lock_waiter *waiter; | |
48 | ||
49 | HMAP_FOR_EACH_WITH_HASH (waiter, session_node, hash_string(lock_name, 0), | |
50 | &session->waiters) { | |
51 | if (!strcmp(lock_name, waiter->lock_name)) { | |
52 | return waiter; | |
53 | } | |
54 | } | |
55 | return NULL; | |
56 | } | |
57 | ||
58 | /* Returns the waiter that owns 'lock'. | |
59 | * | |
60 | * A lock always has an owner, so this function will never return NULL. */ | |
61 | struct ovsdb_lock_waiter * | |
62 | ovsdb_lock_get_owner(const struct ovsdb_lock *lock) | |
63 | { | |
64 | return CONTAINER_OF(list_front(&lock->waiters), | |
65 | struct ovsdb_lock_waiter, lock_node); | |
66 | } | |
67 | ||
68 | /* Removes 'waiter' from its lock's list. This means that, if 'waiter' was | |
69 | * formerly the owner of its lock, then it no longer owns it. | |
70 | * | |
71 | * Returns the session that now owns 'waiter'. This is NULL if 'waiter' was | |
72 | * the lock's owner and no other sessions were waiting for the lock. In this | |
73 | * case, the lock has been destroyed, so the caller must be sure not to refer | |
74 | * to it again. A nonnull return value reflects a change in the lock's | |
75 | * ownership if and only if 'waiter' formerly owned the lock. */ | |
76 | struct ovsdb_session * | |
77 | ovsdb_lock_waiter_remove(struct ovsdb_lock_waiter *waiter) | |
78 | { | |
79 | struct ovsdb_lock *lock = waiter->lock; | |
80 | ||
81 | list_remove(&waiter->lock_node); | |
82 | waiter->lock = NULL; | |
83 | ||
84 | if (list_is_empty(&lock->waiters)) { | |
85 | hmap_remove(&lock->server->locks, &lock->hmap_node); | |
86 | free(lock->name); | |
87 | free(lock); | |
88 | return NULL; | |
89 | } | |
90 | ||
91 | return ovsdb_lock_get_owner(lock)->session; | |
92 | } | |
93 | ||
94 | /* Destroys 'waiter', which must have already been removed from its lock's | |
95 | * waiting list with ovsdb_lock_waiter_remove(). | |
96 | * | |
97 | * Removing and destroying locks are decoupled because a lock initially created | |
98 | * by the "steal" request, that is later stolen by another client, remains in | |
99 | * the database session until the database client sends an "unlock" request. */ | |
100 | void | |
101 | ovsdb_lock_waiter_destroy(struct ovsdb_lock_waiter *waiter) | |
102 | { | |
103 | assert(!waiter->lock); | |
104 | hmap_remove(&waiter->session->waiters, &waiter->session_node); | |
105 | free(waiter->lock_name); | |
106 | free(waiter); | |
107 | } | |
108 | ||
109 | /* Returns true if 'waiter' owns its associated lock. */ | |
110 | bool | |
111 | ovsdb_lock_waiter_is_owner(const struct ovsdb_lock_waiter *waiter) | |
e317253b | 112 | { |
da897f41 | 113 | return waiter->lock && waiter == ovsdb_lock_get_owner(waiter->lock); |
e317253b BP |
114 | } |
115 | ||
116 | /* Initializes 'server' as a server that operates on 'db'. */ | |
117 | void | |
118 | ovsdb_server_init(struct ovsdb_server *server, struct ovsdb *db) | |
119 | { | |
120 | server->db = db; | |
da897f41 | 121 | hmap_init(&server->locks); |
e317253b BP |
122 | } |
123 | ||
124 | /* Destroys 'server'. */ | |
125 | void | |
da897f41 BP |
126 | ovsdb_server_destroy(struct ovsdb_server *server) |
127 | { | |
128 | hmap_destroy(&server->locks); | |
129 | } | |
130 | ||
131 | static struct ovsdb_lock * | |
132 | ovsdb_server_create_lock__(struct ovsdb_server *server, const char *lock_name, | |
133 | uint32_t hash) | |
134 | { | |
135 | struct ovsdb_lock *lock; | |
136 | ||
137 | HMAP_FOR_EACH_WITH_HASH (lock, hmap_node, hash, &server->locks) { | |
138 | if (!strcmp(lock->name, lock_name)) { | |
139 | return lock; | |
140 | } | |
141 | } | |
142 | ||
143 | lock = xzalloc(sizeof *lock); | |
144 | lock->server = server; | |
145 | lock->name = xstrdup(lock_name); | |
146 | hmap_insert(&server->locks, &lock->hmap_node, hash); | |
147 | list_init(&lock->waiters); | |
148 | ||
149 | return lock; | |
150 | } | |
151 | ||
152 | /* Attempts to acquire the lock named 'lock_name' for 'session' within | |
153 | * 'server'. Returns the new lock waiter. | |
154 | * | |
155 | * If 'mode' is OVSDB_LOCK_STEAL, then the new lock waiter is always the owner | |
156 | * of the lock. '*victimp' receives the session of the previous owner or NULL | |
157 | * if the lock was previously unowned. (If the victim itself originally | |
158 | * obtained the lock through a "steal" operation, then this function also | |
159 | * removes the victim from the lock's waiting list.) | |
160 | * | |
161 | * If 'mode' is OVSDB_LOCK_WAIT, then the new lock waiter is the owner of the | |
162 | * lock only if this lock had no existing owner. '*victimp' is set to NULL. */ | |
163 | struct ovsdb_lock_waiter * | |
164 | ovsdb_server_lock(struct ovsdb_server *server, | |
165 | struct ovsdb_session *session, | |
166 | const char *lock_name, | |
167 | enum ovsdb_lock_mode mode, | |
168 | struct ovsdb_session **victimp) | |
e317253b | 169 | { |
da897f41 BP |
170 | uint32_t hash = hash_string(lock_name, 0); |
171 | struct ovsdb_lock_waiter *waiter, *victim; | |
172 | struct ovsdb_lock *lock; | |
173 | ||
174 | lock = ovsdb_server_create_lock__(server, lock_name, hash); | |
175 | victim = (mode == OVSDB_LOCK_STEAL && !list_is_empty(&lock->waiters) | |
176 | ? ovsdb_lock_get_owner(lock) | |
177 | : NULL); | |
178 | ||
179 | waiter = xmalloc(sizeof *waiter); | |
180 | waiter->mode = mode; | |
181 | waiter->lock_name = xstrdup(lock_name); | |
182 | waiter->lock = lock; | |
183 | if (mode == OVSDB_LOCK_STEAL) { | |
184 | list_push_front(&lock->waiters, &waiter->lock_node); | |
185 | } else { | |
186 | list_push_back(&lock->waiters, &waiter->lock_node); | |
187 | } | |
188 | waiter->session = session; | |
189 | hmap_insert(&waiter->session->waiters, &waiter->session_node, hash); | |
190 | ||
191 | if (victim && victim->mode == OVSDB_LOCK_STEAL) { | |
192 | ovsdb_lock_waiter_remove(victim); | |
193 | } | |
194 | *victimp = victim ? victim->session : NULL; | |
195 | ||
196 | return waiter; | |
e317253b | 197 | } |