Add support for base::Closure in the MessageLoop.

base/message_loop.h

 // Copyright (c) 2011 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_H_
 #define BASE_MESSAGE_LOOP_H_
 #pragma once
 
 #include <queue>
 #include <string>
 
 #include "base/base_api.h"
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_pump.h"
 #include "base/observer_list.h"
 #include "base/synchronization/lock.h"
 #include "base/task.h"
+#include "base/time.h"
+#include "base/tracked.h"
 
 #if defined(OS_WIN)
 // We need this to declare base::MessagePumpWin::Dispatcher, which we should
 // really just eliminate.
 #include "base/message_pump_win.h"
 #elif defined(OS_POSIX)
 #include "base/message_pump_libevent.h"
 #if !defined(OS_MACOSX)
 #include "base/message_pump_glib.h"
 typedef struct _XDisplay Display;
 #endif
 #endif
 #if defined(TOUCH_UI)
 #include "base/message_pump_glib_x_dispatch.h"
 #endif
 
 namespace base {
 class Histogram;
 }
 
+#if defined(TRACK_ALL_TASK_OBJECTS)
+namespace tracked_objects {
+class Births;
+}
+#endif  // defined(TRACK_ALL_TASK_OBJECTS)
+
 // 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 or those
 // managed by TimerManager.  Depending on the type of message pump used by the
 // MessageLoop other events such as UI messages may be processed.  On Windows
 // APC calls (as time permits) and signals sent to a registered set of HANDLEs
 // may also be processed.
 //
 // NOTE: Unless otherwise specified, a MessageLoop's methods may only be called
@@ skipping 107 matching lines @@
 
   void PostDelayedTask(
       const tracked_objects::Location& from_here, Task* task, int64 delay_ms);
 
   void PostNonNestableTask(
       const tracked_objects::Location& from_here, Task* task);
 
   void PostNonNestableDelayedTask(
       const tracked_objects::Location& from_here, Task* task, int64 delay_ms);
 
+  // TODO(ajwong): Remove the functions above once the Task -> Closure migration
+  // is complete.
+  //
+  // There are 2 sets of Post*Task functions, one which tasks the older Task*

[joth, 2011/04/16 15:11:57]

nit: one which _takes_

[awong, 2011/04/17 00:34:57]

Done.

+  // function object representation, and one that task the newer base::Closure.

[joth, 2011/04/16 15:11:57]

again, one that _takes_

[awong, 2011/04/17 00:34:57]

Done.

+  // We have this overload to allow a staged transition between the two systems.
+  // Once the transition is done, the functions above should be deleted.
+  void PostTask(
+      const tracked_objects::Location& from_here,
+      const base::Closure& task);
+
+  void PostDelayedTask(
+      const tracked_objects::Location& from_here,
+      const base::Closure& task, int64 delay_ms);
+
+  void PostNonNestableTask(
+      const tracked_objects::Location& from_here,
+      const base::Closure& task);
+
+  void PostNonNestableDelayedTask(
+      const tracked_objects::Location& from_here,
+      const base::Closure& task, int64 delay_ms);
+
   // A variant on PostTask that deletes the given object.  This is useful
   // if the object needs to live until the next run of the MessageLoop (for
   // example, deleting a RenderProcessHost from within an IPC callback is not
   // good).
   //
   // NOTE: This method may be called on any thread.  The object will be deleted
   // on the thread that executes MessageLoop::Run().  If this is not the same
   // as the thread that calls PostDelayedTask(FROM_HERE, ), then T MUST inherit
   // from RefCountedThreadSafe<T>!
   template <class T>
@@ skipping 106 matching lines @@
 
   // A TaskObserver is an object that receives task notifications from the
   // MessageLoop.
   //
   // NOTE: A TaskObserver implementation should be extremely fast!
   class BASE_API TaskObserver {
    public:
     TaskObserver();
 
     // This method is called before processing a task.
-    virtual void WillProcessTask(const Task* task) = 0;
+    virtual void WillProcessTask(base::TimeTicks time_posted) = 0;
 
     // This method is called after processing a task.
-    virtual void DidProcessTask(const Task* task) = 0;
+    virtual void DidProcessTask(base::TimeTicks time_posted) = 0;
 
    protected:
     virtual ~TaskObserver();
   };
 
   // These functions can only be called on the same thread that |this| is
   // running on.
   void AddTaskObserver(TaskObserver* task_observer);
   void RemoveTaskObserver(TaskObserver* task_observer);
 
@@ skipping 43 matching lines @@
    public:
     explicit AutoRunState(MessageLoop* loop);
     ~AutoRunState();
    private:
     MessageLoop* loop_;
     RunState* previous_state_;
   };
 
   // This structure is copied around by value.
   struct PendingTask {
-    PendingTask(Task* task, bool nestable)
-        : task(task), sequence_num(0), nestable(nestable) {
-    }
+    PendingTask(const base::Closure& task,
+                const tracked_objects::Location& posted_from,
+                base::TimeTicks delayed_run_time,
+                bool nestable);
 
     // Used to support sorting.
     bool operator<(const PendingTask& other) const;
 
-    Task* task;                        // The task to run.
-    base::TimeTicks delayed_run_time;  // The time when the task should be run.
-    int sequence_num;                  // Secondary sort key for run time.
-    bool nestable;                     // OK to dispatch from a nested loop.
+    // The task to run.
+    base::Closure task;
+
+#if defined(TRACK_ALL_TASK_OBJECTS)
+    // Counter for location where the Closure was posted from.
+    tracked_objects::Births* post_births;
+#endif  // defined(TRACK_ALL_TASK_OBJECTS)
+
+    // Time this PendingTask was posted.
+    base::TimeTicks time_posted;
+
+    // The time when the task should be run.
+    base::TimeTicks delayed_run_time;
+
+    // Secondary sort key for run time.
+    int sequence_num;
+
+    // OK to dispatch from a nested loop.
+    bool nestable;
   };
 
   class TaskQueue : public std::queue<PendingTask> {
    public:
     void Swap(TaskQueue* queue) {
       c.swap(queue->c);  // Calls std::deque::swap
     }
   };
 
   typedef std::priority_queue<PendingTask> DelayedTaskQueue;
@@ skipping 19 matching lines @@
 #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 task and deletes it.
-  void RunTask(Task* task);
+  // 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);
 
+  // Adds the pending task to our incoming_queue_.
+  //
+  // 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.
+  void AddToIncomingQueue(PendingTask* pending_task);
+
   // 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();
 
-  // Post a task to our incomming queue.
-  void PostTask_Helper(const tracked_objects::Location& from_here, Task* task,
-                       int64 delay_ms, bool nestable);
+  // Calcuates the time at which a PendingTask should run.
+  base::TimeTicks CalculateDelayedRuntime(int64 delay_ms);
 
   // Start recording histogram info about events and action IF it was enabled
   // and IF the statistics recorder can accept a registration of our histogram.
   void StartHistogrammer();
 
   // Add occurence of event to our histogram, so that we can see what is being
   // done in a specific MessageLoop instance (i.e., specific thread).
   // If message_histogram_ is NULL, this is a no-op.
   void HistogramEvent(int event);
 
@@ skipping 28 matching lines @@
   bool nestable_tasks_allowed_;
 
   bool exception_restoration_;
 
   std::string thread_name_;
   // A profiling histogram showing the counts of various messages and events.
   base::Histogram* message_histogram_;
 
   // A null terminated list which creates 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
-  // items that will be handled by the TimerManager.
+  // tasks have not yet been sorted out into items for our work_queue_ vs items
+  // that will be handled by the TimerManager.
   TaskQueue incoming_queue_;
   // Protect access to incoming_queue_.
   mutable base::Lock incoming_queue_lock_;
 
   RunState* state_;
 
+  bool should_leak_tasks_;

[joth, 2011/04/16 15:11:57]

maybe worth putting a comment on this member, if just directing to the subtle
code that uses it

[awong, 2011/04/17 00:34:57]

Good idea! Comment added.

+
 #if defined(OS_WIN)
   base::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.
   int next_sequence_num_;
 
@@ skipping 130 matching lines @@
 #endif  // defined(OS_POSIX)
 };
 
 // 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);
 
 #endif  // BASE_MESSAGE_LOOP_H_