1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
11 #include "base/base_export.h"
12 #include "base/message_loop.h"
13 #include "base/message_loop_proxy.h"
14 #include "base/threading/platform_thread.h"
18 // A simple thread abstraction that establishes a MessageLoop on a new thread.
19 // The consumer uses the MessageLoop of the thread to cause code to execute on
20 // the thread. When this object is destroyed the thread is terminated. All
21 // pending tasks queued on the thread's message loop will run to completion
22 // before the thread is terminated.
24 // After the thread is stopped, the destruction sequence is:
26 // (1) Thread::CleanUp()
27 // (2) MessageLoop::~MessageLoop
28 // (3.b) MessageLoop::DestructionObserver::WillDestroyCurrentMessageLoop
29 class BASE_EXPORT Thread : PlatformThread::Delegate {
32 Options() : message_loop_type(MessageLoop::TYPE_DEFAULT), stack_size(0) {}
33 Options(MessageLoop::Type type, size_t size)
34 : message_loop_type(type), stack_size(size) {}
36 // Specifies the type of message loop that will be allocated on the thread.
37 MessageLoop::Type message_loop_type;
39 // Specifies the maximum stack size that the thread is allowed to use.
40 // This does not necessarily correspond to the thread's initial stack size.
41 // A value of 0 indicates that the default maximum should be used.
46 // name is a display string to identify the thread.
47 explicit Thread(const char* name);
49 // Destroys the thread, stopping it if necessary.
51 // NOTE: If you are subclassing from Thread, and you wish for your CleanUp
52 // method to be called, then you need to call Stop() from your destructor.
56 // Starts the thread. Returns true if the thread was successfully started;
57 // otherwise, returns false. Upon successful return, the message_loop()
58 // getter will return non-null.
60 // Note: This function can't be called on Windows with the loader lock held;
61 // i.e. during a DllMain, global object construction or destruction, atexit()
65 // Starts the thread. Behaves exactly like Start in addition to allow to
66 // override the default options.
68 // Note: This function can't be called on Windows with the loader lock held;
69 // i.e. during a DllMain, global object construction or destruction, atexit()
71 bool StartWithOptions(const Options& options);
73 // Signals the thread to exit and returns once the thread has exited. After
74 // this method returns, the Thread object is completely reset and may be used
75 // as if it were newly constructed (i.e., Start may be called again).
77 // Stop may be called multiple times and is simply ignored if the thread is
80 // NOTE: This method is optional. It is not strictly necessary to call this
81 // method as the Thread's destructor will take care of stopping the thread if
86 // Signals the thread to exit in the near future.
88 // WARNING: This function is not meant to be commonly used. Use at your own
89 // risk. Calling this function will cause message_loop() to become invalid in
90 // the near future. This function was created to workaround a specific
91 // deadlock on Windows with printer worker thread. In any other case, Stop()
94 // StopSoon should not be called multiple times as it is risky to do so. It
95 // could cause a timing issue in message_loop() access. Call Stop() to reset
96 // the thread object once it is known that the thread has quit.
99 // Returns the message loop for this thread. Use the MessageLoop's
100 // PostTask methods to execute code on the thread. This only returns
101 // non-null after a successful call to Start. After Stop has been called,
102 // this will return NULL.
104 // NOTE: You must not call this MessageLoop's Quit method directly. Use
105 // the Thread's Stop method instead.
107 MessageLoop* message_loop() const { return message_loop_; }
109 // Returns a MessageLoopProxy for this thread. Use the MessageLoopProxy's
110 // PostTask methods to execute code on the thread. This only returns
111 // non-NULL after a successful call to Start. After Stop has been called,
112 // this will return NULL. Callers can hold on to this even after the thread
114 // TODO(sanjeevr): Look into merging MessageLoop and MessageLoopProxy.
115 scoped_refptr<MessageLoopProxy> message_loop_proxy() const {
116 return message_loop_->message_loop_proxy();
119 // Set the name of this thread (for display in debugger too).
120 const std::string &thread_name() { return name_; }
122 // The native thread handle.
123 PlatformThreadHandle thread_handle() { return thread_; }
126 PlatformThreadId thread_id() const { return thread_id_; }
128 // Returns true if the thread has been started, and not yet stopped.
129 // When a thread is running, |thread_id_| is a valid id.
130 bool IsRunning() const { return thread_id_ != kInvalidThreadId; }
133 // Called just prior to starting the message loop
134 virtual void Init() {}
136 // Called to start the message loop
137 virtual void Run(MessageLoop* message_loop);
139 // Called just after the message loop ends
140 virtual void CleanUp() {}
142 // Called after the message loop has been deleted. In general clients
143 // should prefer to use CleanUp(). This method is used when code needs to
144 // be run after all of the MessageLoop::DestructionObservers have completed.
145 virtual void CleanUpAfterMessageLoopDestruction() {}
147 static void SetThreadWasQuitProperly(bool flag);
148 static bool GetThreadWasQuitProperly();
150 void set_message_loop(MessageLoop* message_loop) {
151 message_loop_ = message_loop;
155 bool thread_was_started() const { return started_; }
157 // PlatformThread::Delegate methods:
158 virtual void ThreadMain();
160 // Whether we successfully started the thread.
163 // If true, we're in the middle of stopping, and shouldn't access
164 // |message_loop_|. It may non-NULL and invalid.
167 // Used to pass data to ThreadMain.
169 StartupData* startup_data_;
171 // The thread's handle.
172 PlatformThreadHandle thread_;
174 // The thread's message loop. Valid only while the thread is alive. Set
175 // by the created thread.
176 MessageLoop* message_loop_;
179 PlatformThreadId thread_id_;
181 // The name of the thread. Used for debugging purposes.
184 friend class ThreadQuitTask;
186 DISALLOW_COPY_AND_ASSIGN(Thread);
191 #endif // BASE_THREAD_H_