| // Copyright (c) 2009 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef CHROME_BROWSER_CHROME_THREAD_H_ |
| #define CHROME_BROWSER_CHROME_THREAD_H_ |
| |
| #include "base/lock.h" |
| #include "base/task.h" |
| #include "base/thread.h" |
| |
| namespace base { |
| class MessageLoopProxy; |
| } |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // ChromeThread |
| // |
| // This class represents a thread that is known by a browser-wide name. For |
| // example, there is one IO thread for the entire browser process, and various |
| // pieces of code find it useful to retrieve a pointer to the IO thread's |
| // Invoke a task by thread ID: |
| // |
| // ChromeThread::PostTask(ChromeThread::IO, FROM_HERE, task); |
| // |
| // The return value is false if the task couldn't be posted because the target |
| // thread doesn't exist. If this could lead to data loss, you need to check the |
| // result and restructure the code to ensure it doesn't occur. |
| // |
| // This class automatically handles the lifetime of different threads. |
| // It's always safe to call PostTask on any thread. If it's not yet created, |
| // the task is deleted. There are no race conditions. If the thread that the |
| // task is posted to is guaranteed to outlive the current thread, then no locks |
| // are used. You should never need to cache pointers to MessageLoops, since |
| // they're not thread safe. |
| class ChromeThread : public base::Thread { |
| public: |
| // An enumeration of the well-known threads. |
| // NOTE: threads must be listed in the order of their life-time, with each |
| // thread outliving every other thread below it. |
| enum ID { |
| // The main thread in the browser. |
| UI, |
| |
| // This is the thread that interacts with the database. |
| DB, |
| |
| // This is the "main" thread for WebKit within the browser process when |
| // NOT in --single-process mode. |
| WEBKIT, |
| |
| // This is the thread that interacts with the file system. |
| FILE, |
| |
| // Used to launch and terminate processes. |
| PROCESS_LAUNCHER, |
| |
| // This is the thread to handle slow HTTP cache operations. |
| CACHE, |
| |
| // This is the thread that processes IPC and network messages. |
| IO, |
| |
| #if defined(USE_X11) |
| // This thread has a second connection to the X server and is used to |
| // process UI requests when routing the request to the UI thread would risk |
| // deadlock. |
| BACKGROUND_X11, |
| #endif |
| |
| // This identifier does not represent a thread. Instead it counts the |
| // number of well-known threads. Insert new well-known threads before this |
| // identifier. |
| ID_COUNT |
| }; |
| |
| // Construct a ChromeThread with the supplied identifier. It is an error |
| // to construct a ChromeThread that already exists. |
| explicit ChromeThread(ID identifier); |
| |
| // Special constructor for the main (UI) thread and unittests. We use a dummy |
| // thread here since the main thread already exists. |
| ChromeThread(ID identifier, MessageLoop* message_loop); |
| |
| virtual ~ChromeThread(); |
| |
| // These are the same methods in message_loop.h, but are guaranteed to either |
| // get posted to the MessageLoop if it's still alive, or be deleted otherwise. |
| // They return true iff the thread existed and the task was posted. Note that |
| // even if the task is posted, there's no guarantee that it will run, since |
| // the target thread may already have a Quit message in its queue. |
| static bool PostTask(ID identifier, |
| const tracked_objects::Location& from_here, |
| Task* task); |
| static bool PostDelayedTask(ID identifier, |
| const tracked_objects::Location& from_here, |
| Task* task, |
| int64 delay_ms); |
| static bool PostNonNestableTask(ID identifier, |
| const tracked_objects::Location& from_here, |
| Task* task); |
| static bool PostNonNestableDelayedTask( |
| ID identifier, |
| const tracked_objects::Location& from_here, |
| Task* task, |
| int64 delay_ms); |
| |
| template <class T> |
| static bool DeleteSoon(ID identifier, |
| const tracked_objects::Location& from_here, |
| T* object) { |
| return PostNonNestableTask( |
| identifier, from_here, new DeleteTask<T>(object)); |
| } |
| |
| template <class T> |
| static bool ReleaseSoon(ID identifier, |
| const tracked_objects::Location& from_here, |
| T* object) { |
| return PostNonNestableTask( |
| identifier, from_here, new ReleaseTask<T>(object)); |
| } |
| |
| // Callable on any thread. Returns whether the given ID corresponds to a well |
| // known thread. |
| static bool IsWellKnownThread(ID identifier); |
| |
| // Callable on any thread. Returns whether you're currently on a particular |
| // thread. |
| static bool CurrentlyOn(ID identifier); |
| |
| // If the current message loop is one of the known threads, returns true and |
| // sets identifier to its ID. Otherwise returns false. |
| static bool GetCurrentThreadIdentifier(ID* identifier); |
| |
| // Callers can hold on to a refcounted MessageLoopProxy beyond the lifetime |
| // of the thread. |
| static scoped_refptr<base::MessageLoopProxy> GetMessageLoopProxyForThread( |
| ID identifier); |
| |
| // Use these templates in conjuction with RefCountedThreadSafe when you want |
| // to ensure that an object is deleted on a specific thread. This is needed |
| // when an object can hop between threads (i.e. IO -> FILE -> IO), and thread |
| // switching delays can mean that the final IO tasks executes before the FILE |
| // task's stack unwinds. This would lead to the object destructing on the |
| // FILE thread, which often is not what you want (i.e. to unregister from |
| // NotificationService, to notify other objects on the creating thread etc). |
| template<ID thread> |
| struct DeleteOnThread { |
| template<typename T> |
| static void Destruct(T* x) { |
| if (CurrentlyOn(thread)) { |
| delete x; |
| } else { |
| DeleteSoon(thread, FROM_HERE, x); |
| } |
| } |
| }; |
| |
| // Sample usage: |
| // class Foo |
| // : public base::RefCountedThreadSafe< |
| // Foo, ChromeThread::DeleteOnIOThread> { |
| // |
| // ... |
| // private: |
| // friend class ChromeThread; |
| // friend class DeleteTask<Foo>; |
| // |
| // ~Foo(); |
| struct DeleteOnUIThread : public DeleteOnThread<UI> { }; |
| struct DeleteOnIOThread : public DeleteOnThread<IO> { }; |
| struct DeleteOnFileThread : public DeleteOnThread<FILE> { }; |
| struct DeleteOnDBThread : public DeleteOnThread<DB> { }; |
| struct DeleteOnWebKitThread : public DeleteOnThread<WEBKIT> { }; |
| |
| private: |
| // Common initialization code for the constructors. |
| void Initialize(); |
| |
| static bool PostTaskHelper( |
| ID identifier, |
| const tracked_objects::Location& from_here, |
| Task* task, |
| int64 delay_ms, |
| bool nestable); |
| |
| // The identifier of this thread. Only one thread can exist with a given |
| // identifier at a given time. |
| ID identifier_; |
| |
| // This lock protects |chrome_threads_|. Do not read or modify that array |
| // without holding this lock. Do not block while holding this lock. |
| static Lock lock_; |
| |
| // An array of the ChromeThread objects. This array is protected by |lock_|. |
| // The threads are not owned by this array. Typically, the threads are owned |
| // on the UI thread by the g_browser_process object. ChromeThreads remove |
| // themselves from this array upon destruction. |
| static ChromeThread* chrome_threads_[ID_COUNT]; |
| }; |
| |
| #endif // CHROME_BROWSER_CHROME_THREAD_H_ |