| // 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 <memory> |
| #include <string> |
| #include <utility> |
| |
| #include "base/callback.h" |
| #include "base/location.h" |
| #include "base/logging.h" |
| #include "base/macros.h" |
| #include "base/memory/scoped_refptr.h" |
| #include "base/single_thread_task_runner.h" |
| #include "base/task_runner_util.h" |
| #include "base/time/time.h" |
| #include "content/common/content_export.h" |
| #include "content/public/browser/browser_thread.h" |
| |
| namespace content { |
| |
| class BrowserThreadDelegate; |
| class BrowserThreadImpl; |
| |
| // Use DCHECK_CURRENTLY_ON(BrowserThread::ID) to assert that a function can only |
| // be called on the named BrowserThread. |
| #define DCHECK_CURRENTLY_ON(thread_identifier) \ |
| (DCHECK(::content::BrowserThread::CurrentlyOn(thread_identifier)) \ |
| << ::content::BrowserThread::GetDCheckCurrentlyOnErrorMessage( \ |
| thread_identifier)) |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // 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 processes non-blocking IO, i.e. IPC and network. |
| // Blocking I/O should happen in TaskScheduler. |
| IO, |
| |
| // NOTE: do not add new threads here. Instead you should just use |
| // base::Create*TaskRunnerWithTraits. |
| |
| // 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 base::Location& from_here, |
| base::OnceClosure task); |
| static bool PostDelayedTask(ID identifier, |
| const base::Location& from_here, |
| base::OnceClosure task, |
| base::TimeDelta delay); |
| static bool PostNonNestableTask(ID identifier, |
| const base::Location& from_here, |
| base::OnceClosure task); |
| static bool PostNonNestableDelayedTask(ID identifier, |
| const base::Location& from_here, |
| base::OnceClosure task, |
| base::TimeDelta delay); |
| |
| static bool PostTaskAndReply(ID identifier, |
| const base::Location& from_here, |
| base::OnceClosure task, |
| base::OnceClosure reply); |
| |
| template <typename ReturnType, typename ReplyArgType> |
| static bool PostTaskAndReplyWithResult( |
| ID identifier, |
| const base::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)); |
| } |
| |
| // Callback version of PostTaskAndReplyWithResult above. |
| // Though RepeatingCallback is convertible to OnceCallback, we need this since |
| // we cannot use template deduction and object conversion at once on the |
| // overload resolution. |
| // TODO(crbug.com/714018): Update all callers of the Callback version to use |
| // OnceCallback. |
| template <typename ReturnType, typename ReplyArgType> |
| static bool PostTaskAndReplyWithResult( |
| ID identifier, |
| const base::Location& from_here, |
| base::Callback<ReturnType()> task, |
| base::Callback<void(ReplyArgType)> reply) { |
| return PostTaskAndReplyWithResult( |
| identifier, from_here, |
| base::OnceCallback<ReturnType()>(std::move(task)), |
| base::OnceCallback<void(ReplyArgType)>(std::move(reply))); |
| } |
| |
| template <class T> |
| static bool DeleteSoon(ID identifier, |
| const base::Location& from_here, |
| const T* object) { |
| return GetTaskRunnerForThread(identifier)->DeleteSoon(from_here, object); |
| } |
| |
| template <class T> |
| static bool DeleteSoon(ID identifier, |
| const base::Location& from_here, |
| std::unique_ptr<T> object) { |
| return DeleteSoon(identifier, from_here, object.release()); |
| } |
| |
| template <class T> |
| static bool ReleaseSoon(ID identifier, |
| const base::Location& from_here, |
| const T* object) { |
| return GetTaskRunnerForThread(identifier)->ReleaseSoon(from_here, object); |
| } |
| |
| // For use with scheduling non-critical tasks for execution after startup. |
| // The order or execution of tasks posted here is unspecified even when |
| // posting to a SequencedTaskRunner and tasks are not guaranteed to be run |
| // prior to browser shutdown. |
| // When called after the browser startup is complete, will post |task| |
| // to |task_runner| immediately. |
| // Note: see related ContentBrowserClient::PostAfterStartupTask. |
| static void PostAfterStartupTask( |
| const base::Location& from_here, |
| const scoped_refptr<base::TaskRunner>& task_runner, |
| base::OnceClosure task); |
| |
| // 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 you're currently on a particular |
| // thread. To DCHECK this, use the DCHECK_CURRENTLY_ON() macro above. |
| static bool CurrentlyOn(ID identifier) WARN_UNUSED_RESULT; |
| |
| // Deprecated: This is equivalent to IsThreadInitialized(). |
| // 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. |
| // TODO(gab): Replace callers with IsThreadInitialized(). |
| 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. Otherwise returns false. |
| static bool GetCurrentThreadIdentifier(ID* identifier) WARN_UNUSED_RESULT; |
| |
| // Callers can hold on to a refcounted task runner beyond the lifetime |
| // of the thread. |
| static scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunnerForThread( |
| ID identifier); |
| |
| // Sets the delegate for BrowserThread::IO. |
| // |
| // Only one delegate may be registered at a time. The delegate may be |
| // unregistered by providing a nullptr pointer. |
| // |
| // The delegate can only be registered through this call before |
| // BrowserThreadImpl(BrowserThread::IO) is created and unregistered after |
| // it was destroyed and its underlying thread shutdown. |
| static void SetIOThreadDelegate(BrowserThreadDelegate* delegate); |
| |
| // Use these templates in conjunction with RefCountedThreadSafe or scoped_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. UI -> IO -> |
| // UI), and thread switching delays can mean that the final UI tasks executes |
| // before the IO task's stack unwinds. This would lead to the object |
| // destructing on the IO thread, which often is not what you want (i.e. to |
| // unregister from NotificationService, to notify other objects on the |
| // creating thread etc). Note: see base::OnTaskRunnerDeleter and |
| // base::RefCountedDeleteOnSequence to bind to SequencedTaskRunner instead of |
| // specific BrowserThreads. |
| 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 |
| } |
| } |
| } |
| 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, BrowserThread::DeleteOnIOThread> { |
| // |
| // ... |
| // private: |
| // friend struct BrowserThread::DeleteOnThread<BrowserThread::IO>; |
| // friend class base::DeleteHelper<Foo>; |
| // |
| // ~Foo(); |
| // |
| // Sample usage with scoped_ptr: |
| // std::unique_ptr<Foo, BrowserThread::DeleteOnIOThread> ptr; |
| // |
| // Note: see base::OnTaskRunnerDeleter and base::RefCountedDeleteOnSequence to |
| // bind to SequencedTaskRunner instead of specific BrowserThreads. |
| struct DeleteOnUIThread : public DeleteOnThread<UI> { }; |
| struct DeleteOnIOThread : public DeleteOnThread<IO> { }; |
| |
| // Returns an appropriate error message for when DCHECK_CURRENTLY_ON() fails. |
| static std::string GetDCheckCurrentlyOnErrorMessage(ID expected); |
| |
| private: |
| friend class BrowserThreadImpl; |
| |
| BrowserThread() {} |
| DISALLOW_COPY_AND_ASSIGN(BrowserThread); |
| }; |
| |
| } // namespace content |
| |
| #endif // CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_H_ |