| // Copyright 2014 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 IOS_WEB_PUBLIC_WEB_THREAD_H_ |
| #define IOS_WEB_PUBLIC_WEB_THREAD_H_ |
| |
| #include <string> |
| #include <utility> |
| |
| #include "base/callback.h" |
| #include "base/compiler_specific.h" |
| #include "base/location.h" |
| #include "base/logging.h" |
| #include "base/macros.h" |
| #include "base/memory/ref_counted.h" |
| #include "base/single_thread_task_runner.h" |
| #include "base/task_runner_util.h" |
| |
| namespace base { |
| class MessageLoop; |
| } |
| |
| namespace tracked_objects { |
| class Location; |
| } |
| |
| namespace web { |
| |
| class WebThreadDelegate; |
| |
| // Use DCHECK_CURRENTLY_ON(WebThread::ID) to assert that a function can only be |
| // called on the named WebThread. |
| #define DCHECK_CURRENTLY_ON(thread_identifier) \ |
| (DCHECK(::web::WebThread::CurrentlyOn(thread_identifier)) \ |
| << ::web::WebThread::GetDCheckCurrentlyOnErrorMessage(thread_identifier)) |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // WebThread |
| // |
| // Utility functions for threads that are known by name. For example, there is |
| // one IO thread for the entire 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: |
| // |
| // WebThread::PostTask(WebThread::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 WebThread { |
| 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 thread that interacts with the file system. |
| FILE, |
| |
| // This is the thread that processes non-blocking IO, i.e. IPC and network. |
| // Blocking IO should happen on other threads like DB, FILE, |
| // FILE_USER_BLOCKING and CACHE depending on the usage. |
| 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 |
| // SingleThreadTaskRunner 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 as 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. |
| static bool PostTask(ID identifier, |
| const tracked_objects::Location& from_here, |
| base::OnceClosure task); |
| static bool PostDelayedTask(ID identifier, |
| const tracked_objects::Location& from_here, |
| base::OnceClosure task, |
| base::TimeDelta delay); |
| static bool PostNonNestableTask(ID identifier, |
| const tracked_objects::Location& from_here, |
| base::OnceClosure task); |
| static bool PostNonNestableDelayedTask( |
| ID identifier, |
| const tracked_objects::Location& from_here, |
| base::OnceClosure task, |
| base::TimeDelta delay); |
| |
| static bool PostTaskAndReply(ID identifier, |
| const tracked_objects::Location& from_here, |
| base::OnceClosure task, |
| base::OnceClosure reply); |
| |
| template <typename ReturnType, typename ReplyArgType> |
| static bool PostTaskAndReplyWithResult( |
| ID identifier, |
| const tracked_objects::Location& from_here, |
| base::OnceCallback<ReturnType()> task, |
| base::OnceCallback<void(ReplyArgType)> reply) { |
| scoped_refptr<base::SingleThreadTaskRunner> task_runner = |
| GetTaskRunnerForThread(identifier); |
| return base::PostTaskAndReplyWithResult(task_runner.get(), from_here, |
| std::move(task), std::move(reply)); |
| } |
| |
| template <class T> |
| static bool DeleteSoon(ID identifier, |
| const tracked_objects::Location& from_here, |
| const T* object) { |
| return GetTaskRunnerForThread(identifier)->DeleteSoon(from_here, object); |
| } |
| |
| // Callable on any thread. Returns whether the given well-known thread is |
| // initialized. |
| static bool IsThreadInitialized(ID identifier) WARN_UNUSED_RESULT; |
| |
| // Callable on any thread. Returns whether execution is currently on the |
| // given thread. To DCHECK this, use the DCHECK_CURRENTLY_ON() macro above. |
| static bool CurrentlyOn(ID identifier) WARN_UNUSED_RESULT; |
| |
| // 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) WARN_UNUSED_RESULT; |
| |
| // If the current message loop is one of the known threads, returns true and |
| // sets identifier to its ID. |
| static bool GetCurrentThreadIdentifier(ID* identifier) WARN_UNUSED_RESULT; |
| |
| // Callers can hold on to a refcounted SingleThreadTaskRunner beyond the |
| // lifetime of the thread. |
| static scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunnerForThread( |
| ID identifier); |
| |
| // Sets the delegate for the specified WebThread. |
| // |
| // Only one delegate may be registered at a time. Delegates may be |
| // unregistered by providing a nullptr 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, WebThreadDelegate* delegate); |
| |
| // Returns an appropriate error message for when DCHECK_CURRENTLY_ON() fails. |
| static std::string GetDCheckCurrentlyOnErrorMessage(ID expected); |
| |
| // Use these templates in conjunction with RefCountedThreadSafe or |
| // std::unique_ptr 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)) { |
| // Leaks at shutdown are acceptable under normal circumstances, |
| // do not report. |
| } |
| } |
| } |
| template <typename T> |
| inline void operator()(T* ptr) const { |
| enum { type_must_be_complete = sizeof(T) }; |
| Destruct(ptr); |
| } |
| }; |
| |
| // Sample usage with RefCountedThreadSafe: |
| // class Foo |
| // : public base::RefCountedThreadSafe< |
| // Foo, web::WebThread::DeleteOnIOThread> { |
| // |
| // ... |
| // private: |
| // friend struct web::WebThread::DeleteOnThread<web::WebThread::IO>; |
| // friend class base::DeleteHelper<Foo>; |
| // |
| // ~Foo(); |
| // |
| // Sample usage with std::unique_ptr: |
| // std::unique_ptr<Foo, web::WebThread::DeleteOnIOThread> ptr; |
| struct DeleteOnUIThread : public DeleteOnThread<UI> {}; |
| struct DeleteOnIOThread : public DeleteOnThread<IO> {}; |
| struct DeleteOnFileThread : public DeleteOnThread<FILE> {}; |
| struct DeleteOnDBThread : public DeleteOnThread<DB> {}; |
| |
| private: |
| friend class WebThreadImpl; |
| |
| WebThread() {} |
| DISALLOW_COPY_AND_ASSIGN(WebThread); |
| }; |
| |
| } // namespace web |
| |
| #endif // IOS_WEB_PUBLIC_WEB_THREAD_H_ |