1 /* 2 * Copyright (C) 2011 Google Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 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 * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of 14 * its contributors may be used to endorse or promote products derived 15 * from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY 18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY 21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 #ifndef SQLCallbackWrapper_h 29 #define SQLCallbackWrapper_h 30 31 #include "core/dom/ExecutionContext.h" 32 #include "core/dom/ExecutionContextTask.h" 33 #include "wtf/ThreadingPrimitives.h" 34 35 namespace WebCore { 36 37 // A helper class to safely dereference the callback objects held by 38 // SQLStatement and SQLTransaction on the proper thread. The 'wrapped' 39 // callback is dereferenced: 40 // - by destructing the enclosing wrapper - on any thread 41 // - by calling clear() - on any thread 42 // - by unwrapping and then dereferencing normally - on context thread only 43 // Oilpan: ~T must be thread-independent. 44 template<typename T> class SQLCallbackWrapper { 45 DISALLOW_ALLOCATION(); 46 public: SQLCallbackWrapper(PassOwnPtr<T> callback,ExecutionContext * executionContext)47 SQLCallbackWrapper(PassOwnPtr<T> callback, ExecutionContext* executionContext) 48 : m_callback(callback) 49 , m_executionContext(m_callback ? executionContext : 0) 50 { 51 ASSERT(!m_callback || (m_executionContext.get() && m_executionContext->isContextThread())); 52 } 53 ~SQLCallbackWrapper()54 ~SQLCallbackWrapper() 55 { 56 clear(); 57 } 58 trace(Visitor * visitor)59 void trace(Visitor* visitor) { visitor->trace(m_executionContext); } 60 clear()61 void clear() 62 { 63 #if ENABLE(OILPAN) 64 // It's safe to call ~T in non-context-thread. 65 // Implementation classes of ExecutionContext are on-heap. Their 66 // destructors are called in their owner threads. 67 MutexLocker locker(m_mutex); 68 m_callback.clear(); 69 m_executionContext.clear(); 70 #else 71 ExecutionContext* context; 72 OwnPtr<T> callback; 73 { 74 MutexLocker locker(m_mutex); 75 if (!m_callback) { 76 ASSERT(!m_executionContext); 77 return; 78 } 79 if (m_executionContext->isContextThread()) { 80 m_callback.clear(); 81 m_executionContext.clear(); 82 return; 83 } 84 context = m_executionContext.release().leakRef(); 85 callback = m_callback.release(); 86 } 87 context->postTask(SafeReleaseTask::create(callback.release())); 88 #endif 89 } 90 unwrap()91 PassOwnPtr<T> unwrap() 92 { 93 MutexLocker locker(m_mutex); 94 ASSERT(!m_callback || m_executionContext->isContextThread()); 95 m_executionContext.clear(); 96 return m_callback.release(); 97 } 98 99 // Useful for optimizations only, please test the return value of unwrap to be sure. hasCallback()100 bool hasCallback() const { return m_callback; } 101 102 private: 103 #if !ENABLE(OILPAN) 104 class SafeReleaseTask : public ExecutionContextTask { 105 public: create(PassOwnPtr<T> callbackToRelease)106 static PassOwnPtr<SafeReleaseTask> create(PassOwnPtr<T> callbackToRelease) 107 { 108 return adoptPtr(new SafeReleaseTask(callbackToRelease)); 109 } 110 performTask(ExecutionContext * context)111 virtual void performTask(ExecutionContext* context) 112 { 113 ASSERT(m_callbackToRelease && context && context->isContextThread()); 114 m_callbackToRelease.clear(); 115 context->deref(); 116 } 117 isCleanupTask()118 virtual bool isCleanupTask() const { return true; } 119 120 private: SafeReleaseTask(PassOwnPtr<T> callbackToRelease)121 explicit SafeReleaseTask(PassOwnPtr<T> callbackToRelease) 122 : m_callbackToRelease(callbackToRelease) 123 { 124 } 125 126 OwnPtr<T> m_callbackToRelease; 127 }; 128 #endif 129 130 Mutex m_mutex; 131 OwnPtr<T> m_callback; 132 RefPtrWillBeMember<ExecutionContext> m_executionContext; 133 }; 134 135 } // namespace WebCore 136 137 #endif // SQLCallbackWrapper_h 138