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 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 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 } 109 110 DatabaseContext::~DatabaseContext() 111 { 112 // For debug accounting only. We must call this last. The assertions assume 113 // this. 114 DatabaseManager::manager().didDestructDatabaseContext(); 115 } 116 117 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. 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. 140 void DatabaseContext::stop() 141 { 142 stopDatabases(); 143 } 144 145 DatabaseContext* DatabaseContext::backend() 146 { 147 return this; 148 } 149 150 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 } 167 168 bool DatabaseContext::databaseThreadAvailable() 169 { 170 return databaseThread() && !m_hasRequestedTermination; 171 } 172 173 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 } 191 192 bool DatabaseContext::allowDatabaseAccess() const 193 { 194 return toDocument(executionContext())->isActive(); 195 } 196 197 SecurityOrigin* DatabaseContext::securityOrigin() const 198 { 199 return executionContext()->securityOrigin(); 200 } 201 202 bool DatabaseContext::isContextThread() const 203 { 204 return executionContext()->isContextThread(); 205 } 206 207 } // namespace blink 208
