1 /*
2 * Copyright (C) 2008 Apple Inc. All Rights Reserved.
3 * Copyright (C) 2011 Google, Inc. All Rights Reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
15 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
17 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE COMPUTER, INC. OR
18 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
19 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
20 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
21 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
22 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 */
27
28 #include "config.h"
29 #include "modules/webdatabase/DatabaseContext.h"
30
31 #include "core/dom/Document.h"
32 #include "core/dom/ExecutionContext.h"
33 #include "modules/webdatabase/Database.h"
34 #include "modules/webdatabase/DatabaseManager.h"
35 #include "modules/webdatabase/DatabaseTask.h"
36 #include "modules/webdatabase/DatabaseThread.h"
37 #include "platform/weborigin/SchemeRegistry.h"
38 #include "platform/weborigin/SecurityOrigin.h"
39 #include "wtf/Assertions.h"
40
41 namespace blink {
42
43 // How the DatabaseContext Life-Cycle works?
44 // ========================================
45 // ... in other words, who's keeping the DatabaseContext alive and how long does
46 // it need to stay alive?
47 //
48 // The DatabaseContext is referenced from RefPtrs in:
49 // 1. ExecutionContext
50 // 2. Database
51 //
52 // At Birth:
53 // ========
54 // We create a DatabaseContext only when there is a need i.e. the script tries to
55 // open a Database via DatabaseManager::openDatabase().
56 //
57 // The DatabaseContext constructor will call ref(). This lets DatabaseContext keep itself alive.
58 // Note that paired deref() is called from contextDestroyed().
59 //
60 // Once a DatabaseContext is associated with a ExecutionContext, it will
61 // live until after the ExecutionContext destructs. This is true even if
62 // we don't succeed in opening any Databases for that context. When we do
63 // succeed in opening Databases for this ExecutionContext, the Database
64 // will re-use the same DatabaseContext.
65 //
66 // At Shutdown:
67 // ===========
68 // During shutdown, the DatabaseContext needs to:
69 // 1. "outlive" the ExecutionContext.
70 // - This is needed because the DatabaseContext needs to remove itself from the
71 // ExecutionContext's ActiveDOMObject list and ContextLifecycleObserver
72 // list. This removal needs to be executed on the script's thread. Hence, we
73 // rely on the ExecutionContext's shutdown process to call
74 // stop() and contextDestroyed() to give us a chance to clean these up from
75 // the script thread.
76 //
77 // 2. "outlive" the Databases.
78 // - This is because they may make use of the DatabaseContext to execute a close
79 // task and shutdown in an orderly manner. When the Databases are destructed,
80 // they will deref the DatabaseContext from the DatabaseThread.
81 //
82 // During shutdown, the ExecutionContext is shutting down on the script thread
83 // while the Databases are shutting down on the DatabaseThread. Hence, there can be
84 // a race condition as to whether the ExecutionContext or the Databases
85 // destruct first.
86 //
87 // The RefPtrs in the Databases and ExecutionContext will ensure that the
88 // DatabaseContext will outlive both regardless of which of the 2 destructs first.
89
create(ExecutionContext * context)90 PassRefPtrWillBeRawPtr<DatabaseContext> DatabaseContext::create(ExecutionContext* context)
91 {
92 RefPtrWillBeRawPtr<DatabaseContext> self = adoptRefWillBeNoop(new DatabaseContext(context));
93 DatabaseManager::manager().registerDatabaseContext(self.get());
94 return self.release();
95 }
96
DatabaseContext(ExecutionContext * context)97 DatabaseContext::DatabaseContext(ExecutionContext* context)
98 : ActiveDOMObject(context)
99 , m_hasOpenDatabases(false)
100 , m_hasRequestedTermination(false)
101 {
102 // ActiveDOMObject expects this to be called to set internal flags.
103 suspendIfNeeded();
104
105 // For debug accounting only. We must do this before we register the
106 // instance. The assertions assume this.
107 DatabaseManager::manager().didConstructDatabaseContext();
108 }
109
~DatabaseContext()110 DatabaseContext::~DatabaseContext()
111 {
112 // For debug accounting only. We must call this last. The assertions assume
113 // this.
114 DatabaseManager::manager().didDestructDatabaseContext();
115 }
116
trace(Visitor * visitor)117 void DatabaseContext::trace(Visitor* visitor)
118 {
119 #if ENABLE(OILPAN)
120 visitor->trace(m_databaseThread);
121 #endif
122 }
123
124 // This is called if the associated ExecutionContext is destructing while
125 // we're still associated with it. That's our cue to disassociate and shutdown.
126 // To do this, we stop the database and let everything shutdown naturally
127 // because the database closing process may still make use of this context.
128 // It is not safe to just delete the context here.
contextDestroyed()129 void DatabaseContext::contextDestroyed()
130 {
131 RefPtrWillBeRawPtr<DatabaseContext> protector(this);
132 stopDatabases();
133 DatabaseManager::manager().unregisterDatabaseContext(this);
134 ActiveDOMObject::contextDestroyed();
135 }
136
137 // stop() is from stopActiveDOMObjects() which indicates that the owner
138 // LocalFrame is shutting down. Initiate the orderly shutdown by stopping the
139 // associated databases.
stop()140 void DatabaseContext::stop()
141 {
142 stopDatabases();
143 }
144
backend()145 DatabaseContext* DatabaseContext::backend()
146 {
147 return this;
148 }
149
databaseThread()150 DatabaseThread* DatabaseContext::databaseThread()
151 {
152 if (!m_databaseThread && !m_hasOpenDatabases) {
153 // It's OK to ask for the m_databaseThread after we've requested
154 // termination because we're still using it to execute the closing
155 // of the database. However, it is NOT OK to create a new thread
156 // after we've requested termination.
157 ASSERT(!m_hasRequestedTermination);
158
159 // Create the database thread on first request - but not if at least one database was already opened,
160 // because in that case we already had a database thread and terminated it and should not create another.
161 m_databaseThread = DatabaseThread::create();
162 m_databaseThread->start();
163 }
164
165 return m_databaseThread.get();
166 }
167
databaseThreadAvailable()168 bool DatabaseContext::databaseThreadAvailable()
169 {
170 return databaseThread() && !m_hasRequestedTermination;
171 }
172
stopDatabases()173 void DatabaseContext::stopDatabases()
174 {
175 // Though we initiate termination of the DatabaseThread here in
176 // stopDatabases(), we can't clear the m_databaseThread ref till we get to
177 // the destructor. This is because the Databases that are managed by
178 // DatabaseThread still rely on this ref between the context and the thread
179 // to execute the task for closing the database. By the time we get to the
180 // destructor, we're guaranteed that the databases are destructed (which is
181 // why our ref count is 0 then and we're destructing). Then, the
182 // m_databaseThread RefPtr destructor will deref and delete the
183 // DatabaseThread.
184
185 if (databaseThreadAvailable()) {
186 m_hasRequestedTermination = true;
187 // This blocks until the database thread finishes the cleanup task.
188 m_databaseThread->terminate();
189 }
190 }
191
allowDatabaseAccess() const192 bool DatabaseContext::allowDatabaseAccess() const
193 {
194 return toDocument(executionContext())->isActive();
195 }
196
securityOrigin() const197 SecurityOrigin* DatabaseContext::securityOrigin() const
198 {
199 return executionContext()->securityOrigin();
200 }
201
isContextThread() const202 bool DatabaseContext::isContextThread() const
203 {
204 return executionContext()->isContextThread();
205 }
206
207 } // namespace blink
208