| // Copyright (c) 2012 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 CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_H_ |
| #define CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_H_ |
| |
| #include <string> |
| |
| #include "base/basictypes.h" |
| #include "base/callback.h" |
| #include "base/location.h" |
| #include "base/message_loop/message_loop_proxy.h" |
| #include "base/task_runner_util.h" |
| #include "base/time/time.h" |
| #include "content/common/content_export.h" |
| |
| #if defined(UNIT_TEST) |
| #include "base/logging.h" |
| #endif // UNIT_TEST |
| |
| namespace base { |
| class MessageLoop; |
| class SequencedWorkerPool; |
| class Thread; |
| } |
| |
| namespace content { |
| |
| class BrowserThreadDelegate; |
| class BrowserThreadImpl; |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // BrowserThread |
| // |
| // Utility functions for threads that are 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 message loop. |
| // |
| // Invoke a task by thread ID: |
| // |
| // BrowserThread::PostTask(BrowserThread::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 CONTENT_EXPORT BrowserThread { |
| 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. |
| // Deprecated: Do not design new code to use this thread; see |
| // http://crbug.com/106839 |
| WEBKIT_DEPRECATED, |
| |
| // This is the thread that interacts with the file system. |
| FILE, |
| |
| // Used for file system operations that block user interactions. |
| // Responsiveness of this thread affect users. |
| FILE_USER_BLOCKING, |
| |
| // Used to launch and terminate Chrome 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, |
| |
| // NOTE: do not add new threads here that are only used by a small number of |
| // files. Instead you should just use a Thread class and pass its |
| // MessageLoopProxy around. Named threads there are only for threads that |
| // are used in many places. |
| |
| // 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 |
| }; |
| |
| // 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, |
| const base::Closure& task); |
| static bool PostDelayedTask(ID identifier, |
| const tracked_objects::Location& from_here, |
| const base::Closure& task, |
| base::TimeDelta delay); |
| static bool PostNonNestableTask(ID identifier, |
| const tracked_objects::Location& from_here, |
| const base::Closure& task); |
| static bool PostNonNestableDelayedTask( |
| ID identifier, |
| const tracked_objects::Location& from_here, |
| const base::Closure& task, |
| base::TimeDelta delay); |
| |
| static bool PostTaskAndReply( |
| ID identifier, |
| const tracked_objects::Location& from_here, |
| const base::Closure& task, |
| const base::Closure& reply); |
| |
| template <typename ReturnType, typename ReplyArgType> |
| static bool PostTaskAndReplyWithResult( |
| ID identifier, |
| const tracked_objects::Location& from_here, |
| const base::Callback<ReturnType(void)>& task, |
| const base::Callback<void(ReplyArgType)>& reply) { |
| scoped_refptr<base::MessageLoopProxy> message_loop_proxy = |
| GetMessageLoopProxyForThread(identifier); |
| return base::PostTaskAndReplyWithResult( |
| message_loop_proxy.get(), from_here, task, reply); |
| } |
| |
| template <class T> |
| static bool DeleteSoon(ID identifier, |
| const tracked_objects::Location& from_here, |
| const T* object) { |
| return GetMessageLoopProxyForThread(identifier)->DeleteSoon( |
| from_here, object); |
| } |
| |
| template <class T> |
| static bool ReleaseSoon(ID identifier, |
| const tracked_objects::Location& from_here, |
| const T* object) { |
| return GetMessageLoopProxyForThread(identifier)->ReleaseSoon( |
| from_here, object); |
| } |
| |
| // Simplified wrappers for posting to the blocking thread pool. Use this |
| // for doing things like blocking I/O. |
| // |
| // The first variant will run the task in the pool with no sequencing |
| // semantics, so may get run in parallel with other posted tasks. The second |
| // variant will all post a task with no sequencing semantics, and will post a |
| // reply task to the origin TaskRunner upon completion. The third variant |
| // provides sequencing between tasks with the same sequence token name. |
| // |
| // These tasks are guaranteed to run before shutdown. |
| // |
| // If you need to provide different shutdown semantics (like you have |
| // something slow and noncritical that doesn't need to block shutdown), |
| // or you want to manually provide a sequence token (which saves a map |
| // lookup and is guaranteed unique without you having to come up with a |
| // unique string), you can access the sequenced worker pool directly via |
| // GetBlockingPool(). |
| static bool PostBlockingPoolTask(const tracked_objects::Location& from_here, |
| const base::Closure& task); |
| static bool PostBlockingPoolTaskAndReply( |
| const tracked_objects::Location& from_here, |
| const base::Closure& task, |
| const base::Closure& reply); |
| static bool PostBlockingPoolSequencedTask( |
| const std::string& sequence_token_name, |
| const tracked_objects::Location& from_here, |
| const base::Closure& task); |
| |
| // Returns the thread pool used for blocking file I/O. Use this object to |
| // perform random blocking operations such as file writes or querying the |
| // Windows registry. |
| static base::SequencedWorkerPool* GetBlockingPool(); |
| |
| // 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); |
| |
| // Callable on any thread. Returns whether the threads message loop is valid. |
| // If this returns false it means the thread is in the process of shutting |
| // down. |
| static bool IsMessageLoopValid(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); |
| |
| // Returns a pointer to the thread's message loop, which will become |
| // invalid during shutdown, so you probably shouldn't hold onto it. |
| // |
| // This must not be called before the thread is started, or after |
| // the thread is stopped, or it will DCHECK. |
| // |
| // Ownership remains with the BrowserThread implementation, so you |
| // must not delete the pointer. |
| static base::MessageLoop* UnsafeGetMessageLoopForThread(ID identifier); |
| |
| // Sets the delegate for the specified BrowserThread. |
| // |
| // Only one delegate may be registered at a time. Delegates may be |
| // unregistered by providing a NULL pointer. |
| // |
| // If the caller unregisters a delegate before CleanUp has been |
| // called, it must perform its own locking to ensure the delegate is |
| // not deleted while unregistering. |
| static void SetDelegate(ID identifier, BrowserThreadDelegate* delegate); |
| |
| // 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(const T* x) { |
| if (CurrentlyOn(thread)) { |
| delete x; |
| } else { |
| if (!DeleteSoon(thread, FROM_HERE, x)) { |
| #if defined(UNIT_TEST) |
| // Only logged under unit testing because leaks at shutdown |
| // are acceptable under normal circumstances. |
| LOG(ERROR) << "DeleteSoon failed on thread " << thread; |
| #endif // UNIT_TEST |
| } |
| } |
| } |
| }; |
| |
| // Sample usage: |
| // class Foo |
| // : public base::RefCountedThreadSafe< |
| // Foo, BrowserThread::DeleteOnIOThread> { |
| // |
| // ... |
| // private: |
| // friend struct BrowserThread::DeleteOnThread<BrowserThread::IO>; |
| // friend class base::DeleteHelper<Foo>; |
| // |
| // ~Foo(); |
| struct DeleteOnUIThread : public DeleteOnThread<UI> { }; |
| struct DeleteOnIOThread : public DeleteOnThread<IO> { }; |
| struct DeleteOnFileThread : public DeleteOnThread<FILE> { }; |
| struct DeleteOnDBThread : public DeleteOnThread<DB> { }; |
| |
| private: |
| friend class BrowserThreadImpl; |
| |
| BrowserThread() {} |
| DISALLOW_COPY_AND_ASSIGN(BrowserThread); |
| }; |
| |
| } // namespace content |
| |
| #endif // CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_H_ |