Made MessagePump a non-thread safe class.

base/message_loop/message_loop.h

 // Copyright 2013 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 BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_
 #define BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_
 
 #include <queue>
 #include <string>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/location.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/message_loop/message_pump.h"
 #include "base/observer_list.h"
 #include "base/pending_task.h"
 #include "base/sequenced_task_runner_helpers.h"
 #include "base/synchronization/lock.h"
 #include "base/tracking_info.h"
 #include "base/time.h"
 
 #if defined(OS_WIN)
@@ skipping 14 matching lines @@
 #include "base/message_loop/message_pump_gtk.h"
 #endif
 
 #endif
 #endif
 
 namespace base {
 
 class HistogramBase;
 class MessageLoopLockTest;
+class MessageLoopProxyImpl;
 class RunLoop;
 class ThreadTaskRunnerHandle;
 #if defined(OS_ANDROID)
 class MessagePumpForUI;
 #endif
 
 // A MessageLoop is used to process events for a particular thread.  There is
 // at most one MessageLoop instance per thread.
 //
 // Events include at a minimum Task instances submitted to PostTask and its
@@ skipping 215 matching lines @@
   Type type() const { return type_; }
 
   // Optional call to connect the thread name with this loop.
   void set_thread_name(const std::string& thread_name) {
     DCHECK(thread_name_.empty()) << "Should not rename this thread!";
     thread_name_ = thread_name;
   }
   const std::string& thread_name() const { return thread_name_; }
 
   // Gets the message loop proxy associated with this message loop.
-  scoped_refptr<MessageLoopProxy> message_loop_proxy() {
-    return message_loop_proxy_.get();
-  }
+  scoped_refptr<MessageLoopProxy> message_loop_proxy();
 
   // Enables or disables the recursive task processing. This happens in the case
   // of recursive message loops. Some unwanted message loop may occurs when
   // using common controls or printer functions. By default, recursive task
   // processing is disabled.
   //
   // Please utilize |ScopedNestableTaskAllower| instead of calling these methods
   // directly.  In general nestable message loops are to be avoided.  They are
   // dangerous and difficult to get right, so please use with extreme caution.
   //
@@ skipping 97 matching lines @@
 #if defined(OS_WIN)
   MessagePumpWin* pump_win() {
     return static_cast<MessagePumpWin*>(pump_.get());
   }
 #elif defined(OS_POSIX) && !defined(OS_IOS)
   MessagePumpLibevent* pump_libevent() {
     return static_cast<MessagePumpLibevent*>(pump_.get());
   }
 #endif
 
-  scoped_refptr<MessagePump> pump_;
+  scoped_ptr<MessagePump> pump_;
 
  private:
   friend class RunLoop;
   friend class MessageLoopLockTest;
+  friend class MessageLoopProxyImpl;
 
   // A function to encapsulate all the exception handling capability in the
   // stacks around the running of a main message loop.  It will run the message
   // loop in a SEH try block or not depending on the set_SEH_restoration()
   // flag invoking respectively RunInternalInSEHFrame() or RunInternal().
   void RunHandler();
 
 #if defined(OS_WIN)
   __declspec(noinline) void RunInternalInSEHFrame();
 #endif
 
   // A surrounding stack frame around the running of the message loop that
   // supports all saving and restoring of state, as is needed for any/all (ugly)
   // recursive calls.
   void RunInternal();
 
   // Called to process any delayed non-nestable tasks.
   bool ProcessNextDelayedNonNestableTask();
 
   // Runs the specified PendingTask.
   void RunTask(const PendingTask& pending_task);
 
   // Calls RunTask or queues the pending_task on the deferred task list if it
   // cannot be run right now.  Returns true if the task was run.
   bool DeferOrRunPendingTask(const PendingTask& pending_task);
 
   // Adds the pending task to delayed_work_queue_.
   void AddToDelayedWorkQueue(const PendingTask& pending_task);
 
-  // This function attempts to add pending task to our incoming_queue_.
-  // The append can only possibly fail when |use_try_lock| is true.
+  // Adds a task to our incoming_queue_. This method can be called on any thread
+  // and the caller is responsible for synchronizing calls to this method.
+  // (Currently |message_loop_proxy_->message_loop_lock_| is used).
   //
-  // When |use_try_lock| is true, then this call will avoid blocking if
-  // the related lock is already held, and will in that case (when the
-  // lock is contended) fail to perform the append, and will return false.
-  //
-  // If the call succeeds to append to the queue, then this call
-  // will return true.
-  //
-  // In all cases, the caller retains ownership of |pending_task|, but this
-  // function will reset the value of pending_task->task.  This is needed to
-  // ensure that the posting call stack does not retain pending_task->task
-  // beyond this function call.
-  bool AddToIncomingQueue(PendingTask* pending_task, bool use_try_lock);
+  // The method takes ownership of |task|.
+  void AddToIncomingQueue(const tracked_objects::Location& from_here,
+                          const Closure& task,
+                          TimeDelta delay,
+                          bool nestable);
 
   // Load tasks from the incoming_queue_ into work_queue_ if the latter is
   // empty.  The former requires a lock to access, while the latter is directly
   // accessible on this thread.
   void ReloadWorkQueue();
 
   // Delete tasks that haven't run yet without running them.  Used in the
   // destructor to make sure all the task's destructors get called.  Returns
   // true if some work was done.
   bool DeletePendingTasks();
@@ skipping 39 matching lines @@
   bool nestable_tasks_allowed_;
 
   bool exception_restoration_;
 
   std::string thread_name_;
   // A profiling histogram showing the counts of various messages and events.
   HistogramBase* message_histogram_;
 
   // An incoming queue of tasks that are acquired under a mutex for processing
   // on this instance's thread. These tasks have not yet been sorted out into
-  // items for our work_queue_ vs delayed_work_queue_.
+  // items for our work_queue_ vs delayed_work_queue_. Protected by
+  // |message_loop_proxy_->message_loop_lock_|.

[rvargas (doing something else), 2013/06/28 03:00:51]

I'm not really comfortable with this pattern of protecting a member with a lock
that belongs to another class.

I think it is better to keep interactions at the method call level: stating that
the caller of AddToIncomingQueue() is responsible for the synchronization is
fine.

[alexeypa (please no reviews), 2013/06/28 17:00:57]

Done.

   TaskQueue incoming_queue_;
-  // Protect access to incoming_queue_.
-  mutable Lock incoming_queue_lock_;
 
   RunLoop* run_loop_;
 
 #if defined(OS_WIN)
   TimeTicks high_resolution_timer_expiration_;
   // Should be set to true before calling Windows APIs like TrackPopupMenu, etc
   // which enter a modal message loop.
   bool os_modal_loop_;
 #endif
 
   // The next sequence number to use for delayed tasks. Updating this counter is
-  // protected by incoming_queue_lock_.
+  // protected by |message_loop_proxy_->message_loop_lock_|.
   int next_sequence_num_;
 
   ObserverList<TaskObserver> task_observers_;
 
-  // The message loop proxy associated with this message loop, if one exists.
-  scoped_refptr<MessageLoopProxy> message_loop_proxy_;
+  // The message loop proxy associated with this message loop.
+  scoped_refptr<MessageLoopProxyImpl> message_loop_proxy_;
   scoped_ptr<ThreadTaskRunnerHandle> thread_task_runner_handle_;
 
   template <class T, class R> friend class base::subtle::DeleteHelperInternal;
   template <class T, class R> friend class base::subtle::ReleaseHelperInternal;
 
   void DeleteSoonInternal(const tracked_objects::Location& from_here,
                           void(*deleter)(const void*),
                           const void* object);
   void ReleaseSoonInternal(const tracked_objects::Location& from_here,
                            void(*releaser)(const void*),
@@ skipping 175 matching lines @@
 
 // Do not add any member variables to MessageLoopForIO!  This is important b/c
 // MessageLoopForIO is often allocated via MessageLoop(TYPE_IO).  Any extra
 // data that you need should be stored on the MessageLoop's pump_ instance.
 COMPILE_ASSERT(sizeof(MessageLoop) == sizeof(MessageLoopForIO),
                MessageLoopForIO_should_not_have_extra_member_variables);
 
 }  // namespace base
 
 #endif  // BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_