Add support for base::Closure in the MessageLoop.

base/message_loop.cc

Index: base/message_loop.cc
diff --git a/base/message_loop.cc b/base/message_loop.cc
index 85e37d4266eeef3986205e01047f00bd595e7a52..1fb4ee73224fec338a77416eca1dc91349f690c5 100644
--- a/base/message_loop.cc
+++ b/base/message_loop.cc
@@ -1,23 +1,21 @@
-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// 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.
 
 #include "base/message_loop.h"
 
-#if defined(OS_POSIX) && !defined(OS_MACOSX)
-#include <gdk/gdk.h>
-#include <gdk/gdkx.h>
-#endif
-
 #include <algorithm>
 
+#include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/message_pump_default.h"
 #include "base/metrics/histogram.h"
+#include "base/scoped_ptr.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
 #include "base/threading/thread_local.h"
+#include "base/tracked_objects.h"
 
 #if defined(OS_MACOSX)
 #include "base/message_pump_mac.h"
@@ -26,6 +24,8 @@
 #include "base/message_pump_libevent.h"
 #endif
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
+#include <gdk/gdk.h>
+#include <gdk/gdkx.h>
 #include "base/message_pump_glib.h"
 #endif
 #if defined(TOUCH_UI)
@@ -81,6 +81,40 @@ const base::LinearHistogram::DescriptionPair event_descriptions_[] = {
 
 bool enable_histogrammer_ = false;
 
+// TODO(ajwong): This is one use case for a Owned() tag that behaves like a
+// "Unique" pointer.  If we had that, and Tasks were always safe to delete on
+// MessageLoop shutdown, this class could just be a function.
+class TaskClosureAdapter : public base::RefCounted<TaskClosureAdapter> {
+ public:
+  // |should_leak_task| points to a flag variable that can be used to determine
+  // if this class should leak the Task on destruction.  This is important
+  // at MessageLoop shutdown since not all tasks can be safely deleted without
+  // running.  See MessageLoop::DeletePendingClosures() for the exact behavior
+  // of when a Task should be deleted. It is subtle.
+  TaskClosureAdapter(Task* task, bool* should_leak_task)
+      : task_(task),
+        should_leak_task_(should_leak_task) {
+  }
+
+  void Run() {
+    task_->Run();
+    delete task_;
+    task_ = NULL;
+  }
+
+ private:
+  friend class base::RefCounted<TaskClosureAdapter>;
+
+  ~TaskClosureAdapter() {
+    if (!*should_leak_task_) {
+      delete task_;
+    }
+  }
+
+  Task* task_;
+  bool* should_leak_task_;
+};
+
 }  // namespace
 
 //------------------------------------------------------------------------------
@@ -107,10 +141,10 @@ static LPTOP_LEVEL_EXCEPTION_FILTER GetTopSEHFilter() {
 
 //------------------------------------------------------------------------------
 
-MessageLoop::TaskObserver::TaskObserver() {
+MessageLoop::ClosureObserver::ClosureObserver() {
 }
 
-MessageLoop::TaskObserver::~TaskObserver() {
+MessageLoop::ClosureObserver::~ClosureObserver() {
 }
 
 MessageLoop::DestructionObserver::~DestructionObserver() {
@@ -123,6 +157,7 @@ MessageLoop::MessageLoop(Type type)
       nestable_tasks_allowed_(true),
       exception_restoration_(false),
       state_(NULL),
+      should_leak_tasks_(true),
       next_sequence_num_(0) {
   DCHECK(!current()) << "should only have one message loop per thread";
   lazy_tls_ptr.Pointer()->Set(this);
@@ -172,10 +207,10 @@ MessageLoop::~MessageLoop() {
   // is being stubborn.  Inspect the queues to see who is left.
   bool did_work;
   for (int i = 0; i < 100; ++i) {
-    DeletePendingTasks();
+    DeletePendingClosures();
     ReloadWorkQueue();
     // If we end up with empty queues, then break out of the loop.
-    did_work = DeletePendingTasks();
+    did_work = DeletePendingClosures();
     if (!did_work)
       break;
   }
@@ -216,22 +251,78 @@ void MessageLoop::RemoveDestructionObserver(
 
 void MessageLoop::PostTask(
     const tracked_objects::Location& from_here, Task* task) {
-  PostTask_Helper(from_here, task, 0, true);
+  PendingClosure pending_closure(
+      base::Bind(&TaskClosureAdapter::Run,
+                 new TaskClosureAdapter(task, &should_leak_tasks_)),
+      from_here,
+      CalculateDelayedRuntime(0), true);
+  // TODO(ajwong): This failed because pending_closure outlives the add to the
+  // incoming_queue_.
+  AddToIncomingQueue(&pending_closure);
 }
 
 void MessageLoop::PostDelayedTask(
     const tracked_objects::Location& from_here, Task* task, int64 delay_ms) {
-  PostTask_Helper(from_here, task, delay_ms, true);
+  PendingClosure pending_closure(
+      base::Bind(&TaskClosureAdapter::Run,
+                 new TaskClosureAdapter(task, &should_leak_tasks_)),
+      from_here,
+      CalculateDelayedRuntime(delay_ms), true);
+  AddToIncomingQueue(&pending_closure);
 }
 
 void MessageLoop::PostNonNestableTask(
     const tracked_objects::Location& from_here, Task* task) {
-  PostTask_Helper(from_here, task, 0, false);
+  PendingClosure pending_closure(
+      base::Bind(&TaskClosureAdapter::Run,
+                 new TaskClosureAdapter(task, &should_leak_tasks_)),
+      from_here,
+      CalculateDelayedRuntime(0), false);
+  AddToIncomingQueue(&pending_closure);
 }
 
 void MessageLoop::PostNonNestableDelayedTask(
     const tracked_objects::Location& from_here, Task* task, int64 delay_ms) {
-  PostTask_Helper(from_here, task, delay_ms, false);
+  PendingClosure pending_closure(
+      base::Bind(&TaskClosureAdapter::Run,
+                 new TaskClosureAdapter(task, &should_leak_tasks_)),
+      from_here,
+      CalculateDelayedRuntime(delay_ms), false);
+  AddToIncomingQueue(&pending_closure);
+}
+
+void MessageLoop::PostClosure(
+    const tracked_objects::Location& from_here, const base::Closure& closure) {
+  DCHECK(!closure.is_null());
+  PendingClosure pending_closure(closure, from_here,
+                                 CalculateDelayedRuntime(0), true);
+  AddToIncomingQueue(&pending_closure);
+}
+
+void MessageLoop::PostDelayedClosure(
+    const tracked_objects::Location& from_here, const base::Closure& closure,
+    int64 delay_ms) {
+  DCHECK(!closure.is_null());
+  PendingClosure pending_closure(closure, from_here,
+                                 CalculateDelayedRuntime(delay_ms), true);
+  AddToIncomingQueue(&pending_closure);
+}
+
+void MessageLoop::PostNonNestableClosure(
+    const tracked_objects::Location& from_here, const base::Closure& closure) {
+  DCHECK(!closure.is_null());
+  PendingClosure pending_closure(closure, from_here,
+                                 CalculateDelayedRuntime(0), false);
+  AddToIncomingQueue(&pending_closure);
+}
+
+void MessageLoop::PostNonNestableDelayedClosure(
+    const tracked_objects::Location& from_here, const base::Closure& closure,
+    int64 delay_ms) {
+  DCHECK(!closure.is_null());
+  PendingClosure pending_closure(closure, from_here,
+                                 CalculateDelayedRuntime(delay_ms), false);
+  AddToIncomingQueue(&pending_closure);
 }
 
 void MessageLoop::Run() {
@@ -281,14 +372,14 @@ bool MessageLoop::IsNested() {
   return state_->run_depth > 1;
 }
 
-void MessageLoop::AddTaskObserver(TaskObserver* task_observer) {
+void MessageLoop::AddClosureObserver(ClosureObserver* closure_observer) {
   DCHECK_EQ(this, current());
-  task_observers_.AddObserver(task_observer);
+  closure_observers_.AddObserver(closure_observer);
 }
 
-void MessageLoop::RemoveTaskObserver(TaskObserver* task_observer) {
+void MessageLoop::RemoveClosureObserver(ClosureObserver* closure_observer) {
   DCHECK_EQ(this, current());
-  task_observers_.RemoveObserver(task_observer);
+  closure_observers_.RemoveObserver(closure_observer);
 }
 
 void MessageLoop::AssertIdle() const {
@@ -349,31 +440,40 @@ bool MessageLoop::ProcessNextDelayedNonNestableTask() {
   if (deferred_non_nestable_work_queue_.empty())
     return false;
 
-  Task* task = deferred_non_nestable_work_queue_.front().task;
+  PendingClosure pending_closure = deferred_non_nestable_work_queue_.front();
   deferred_non_nestable_work_queue_.pop();
 
-  RunTask(task);
+  RunClosure(pending_closure);
   return true;
 }
 
-void MessageLoop::RunTask(Task* task) {
+void MessageLoop::RunClosure(const PendingClosure& pending_closure) {
   DCHECK(nestable_tasks_allowed_);
   // Execute the task and assume the worst: It is probably not reentrant.
   nestable_tasks_allowed_ = false;
 
   HistogramEvent(kTaskRunEvent);
-  FOR_EACH_OBSERVER(TaskObserver, task_observers_,
-                    WillProcessTask(task));
-  task->Run();
-  FOR_EACH_OBSERVER(TaskObserver, task_observers_, DidProcessTask(task));
-  delete task;
+  FOR_EACH_OBSERVER(ClosureObserver, closure_observers_,
+                    WillProcessClosure(pending_closure.time_posted));
+  pending_closure.closure.Run();
+  FOR_EACH_OBSERVER(ClosureObserver, closure_observers_,
+                    DidProcessClosure(pending_closure.time_posted));
+
+#if defined(TRACK_ALL_TASK_OBJECTS)
+  if (tracked_objects::ThreadData::IsActive() && pending_closure.post_births) {
+    tracked_objects::ThreadData::current()->TallyADeath(
+        *pending_closure.post_births,
+        TimeTicks::Now() - pending_closure.time_posted);
+  }
+#endif  // defined(TRACK_ALL_TASK_OBJECTS)
 
   nestable_tasks_allowed_ = true;
 }
 
-bool MessageLoop::DeferOrRunPendingTask(const PendingTask& pending_task) {
-  if (pending_task.nestable || state_->run_depth == 1) {
-    RunTask(pending_task.task);
+bool MessageLoop::DeferOrRunPendingClosure(
+    const PendingClosure& pending_closure) {
+  if (pending_closure.nestable || state_->run_depth == 1) {
+    RunClosure(pending_closure);
     // Show that we ran a task (Note: a new one might arrive as a
     // consequence!).
     return true;
@@ -381,18 +481,18 @@ bool MessageLoop::DeferOrRunPendingTask(const PendingTask& pending_task) {
 
   // We couldn't run the task now because we're in a nested message loop
   // and the task isn't nestable.
-  deferred_non_nestable_work_queue_.push(pending_task);
+  deferred_non_nestable_work_queue_.push(pending_closure);
   return false;
 }
 
-void MessageLoop::AddToDelayedWorkQueue(const PendingTask& pending_task) {
+void MessageLoop::AddToDelayedWorkQueue(const PendingClosure& pending_closure) {
   // Move to the delayed work queue.  Initialize the sequence number
   // before inserting into the delayed_work_queue_.  The sequence number
   // is used to faciliate FIFO sorting when two tasks have the same
   // delayed_run_time value.
-  PendingTask new_pending_task(pending_task);
-  new_pending_task.sequence_num = next_sequence_num_++;
-  delayed_work_queue_.push(new_pending_task);
+  PendingClosure new_pending_closure(pending_closure);
+  new_pending_closure.sequence_num = next_sequence_num_++;
+  delayed_work_queue_.push(new_pending_closure);
 }
 
 void MessageLoop::ReloadWorkQueue() {
@@ -413,62 +513,50 @@ void MessageLoop::ReloadWorkQueue() {
   }
 }
 
-bool MessageLoop::DeletePendingTasks() {
+bool MessageLoop::DeletePendingClosures() {
   bool did_work = !work_queue_.empty();
+  // TODO(darin): Delete all tasks once it is safe to do so.
+  // Until it is totally safe, just do it when running Purify or
+  // Valgrind.
+  //
+#if defined(PURIFY) || defined(USE_HEAPCHECKER)
+  should_leak_tasks_ = false;
+#else
+      if (RunningOnValgrind())
+        should_leak_tasks_ = false;
+#endif  // defined(OS_POSIX)
   while (!work_queue_.empty()) {
-    PendingTask pending_task = work_queue_.front();
+    PendingClosure pending_closure = work_queue_.front();
     work_queue_.pop();
-    if (!pending_task.delayed_run_time.is_null()) {
+    if (!pending_closure.delayed_run_time.is_null()) {
       // We want to delete delayed tasks in the same order in which they would
       // normally be deleted in case of any funny dependencies between delayed
       // tasks.
-      AddToDelayedWorkQueue(pending_task);
-    } else {
-      // TODO(darin): Delete all tasks once it is safe to do so.
-      // Until it is totally safe, just do it when running Purify or
-      // Valgrind.
-#if defined(PURIFY) || defined(USE_HEAPCHECKER)
-      delete pending_task.task;
-#else
-      if (RunningOnValgrind())
-        delete pending_task.task;
-#endif  // defined(OS_POSIX)
+      AddToDelayedWorkQueue(pending_closure);
     }
   }
   did_work |= !deferred_non_nestable_work_queue_.empty();
   while (!deferred_non_nestable_work_queue_.empty()) {
-    // TODO(darin): Delete all tasks once it is safe to do so.
-    // Until it is totaly safe, only delete them under Purify and Valgrind.
-    Task* task = NULL;
-#if defined(PURIFY) || defined(USE_HEAPCHECKER)
-    task = deferred_non_nestable_work_queue_.front().task;
-#else
-    if (RunningOnValgrind())
-      task = deferred_non_nestable_work_queue_.front().task;
-#endif
     deferred_non_nestable_work_queue_.pop();
-    if (task)
-      delete task;
   }
   did_work |= !delayed_work_queue_.empty();
+
+  // Historically, we always delete the task regardless of valgrind status. It's
+  // not completely clear why we want to leak them in the loops above.  This
+  // code is replicating legacy behavior, and should not be considered
+  // absolutely "correct" behavior.

[awong, 2011/04/10 15:58:12]

Hey Darin, do you know the rationale behind why we do this funky dance in
DeletePendingClosure() where we leak

  1) tasks in the work_queue_ w/o a delayed_run_time
  2) all tasks in the deferred_non_nestable_work_queue_

but not the others?

I would have expected that you would either leaked all tasks in all queues or
deleted all tasks.

I think we're leaking the tasks out of work_queue_ because we can't reschedule
them w/o a delayed_run_time.  I don't understand why we're leaking tasks from
the deferred_non_nestable_work_queue_.

If you have any insight into this algorithm, I'd like to update this comment
with the rationale for why we have this behavior.

+  should_leak_tasks_ = false;
   while (!delayed_work_queue_.empty()) {
-    Task* task = delayed_work_queue_.top().task;
     delayed_work_queue_.pop();
-    delete task;
   }
+  should_leak_tasks_ = true;
   return did_work;
 }
 
-// Possibly called on a background thread!
-void MessageLoop::PostTask_Helper(
-    const tracked_objects::Location& from_here, Task* task, int64 delay_ms,
-    bool nestable) {
-  task->SetBirthPlace(from_here);
-
-  PendingTask pending_task(task, nestable);
-
+TimeTicks MessageLoop::CalculateDelayedRuntime(int64 delay_ms) {
+  TimeTicks delayed_run_time;
   if (delay_ms > 0) {
-    pending_task.delayed_run_time =
+    delayed_run_time =
         TimeTicks::Now() + TimeDelta::FromMilliseconds(delay_ms);
 
 #if defined(OS_WIN)
@@ -500,6 +588,11 @@ void MessageLoop::PostTask_Helper(
   }
 #endif
 
+  return delayed_run_time;
+}
+
+// Possibly called on a background thread!
+void MessageLoop::AddToIncomingQueue(PendingClosure* pending_closure) {
   // Warning: Don't try to short-circuit, and handle this thread's tasks more
   // directly, as it could starve handling of foreign threads.  Put every task
   // into this queue.
@@ -509,7 +602,8 @@ void MessageLoop::PostTask_Helper(
     base::AutoLock locked(incoming_queue_lock_);
 
     bool was_empty = incoming_queue_.empty();
-    incoming_queue_.push(pending_task);
+    incoming_queue_.push(*pending_closure);
+    pending_closure->closure.Reset();
     if (!was_empty)
       return;  // Someone else should have started the sub-pump.
 
@@ -558,15 +652,15 @@ bool MessageLoop::DoWork() {
 
     // Execute oldest task.
     do {
-      PendingTask pending_task = work_queue_.front();
+      PendingClosure pending_closure = work_queue_.front();
       work_queue_.pop();
-      if (!pending_task.delayed_run_time.is_null()) {
-        AddToDelayedWorkQueue(pending_task);
+      if (!pending_closure.delayed_run_time.is_null()) {
+        AddToDelayedWorkQueue(pending_closure);
         // If we changed the topmost task, then it is time to re-schedule.
-        if (delayed_work_queue_.top().task == pending_task.task)
-          pump_->ScheduleDelayedWork(pending_task.delayed_run_time);
+        if (delayed_work_queue_.top().closure.Equals(pending_closure.closure))
+          pump_->ScheduleDelayedWork(pending_closure.delayed_run_time);
       } else {
-        if (DeferOrRunPendingTask(pending_task))
+        if (DeferOrRunPendingClosure(pending_closure))
           return true;
       }
     } while (!work_queue_.empty());
@@ -576,7 +670,7 @@ bool MessageLoop::DoWork() {
   return false;
 }
 
-bool MessageLoop::DoDelayedWork(base::TimeTicks* next_delayed_work_time) {
+bool MessageLoop::DoDelayedWork(TimeTicks* next_delayed_work_time) {
   if (!nestable_tasks_allowed_ || delayed_work_queue_.empty()) {
     recent_time_ = *next_delayed_work_time = TimeTicks();
     return false;
@@ -598,13 +692,13 @@ bool MessageLoop::DoDelayedWork(base::TimeTicks* next_delayed_work_time) {
     }
   }
 
-  PendingTask pending_task = delayed_work_queue_.top();
+  PendingClosure pending_closure = delayed_work_queue_.top();
   delayed_work_queue_.pop();
 
   if (!delayed_work_queue_.empty())
     *next_delayed_work_time = delayed_work_queue_.top().delayed_run_time;
 
-  return DeferOrRunPendingTask(pending_task);
+  return DeferOrRunPendingClosure(pending_closure);
 }
 
 bool MessageLoop::DoIdleWork() {
@@ -642,9 +736,32 @@ MessageLoop::AutoRunState::~AutoRunState() {
 }
 
 //------------------------------------------------------------------------------
-// MessageLoop::PendingTask
+// MessageLoop::PendingClosure
+
+MessageLoop::PendingClosure::PendingClosure(
+    const base::Closure& closure,
+    const tracked_objects::Location& posted_from,
+    TimeTicks delayed_run_time,
+    bool nestable)
+    : closure(closure),
+      time_posted(TimeTicks::Now()),
+      delayed_run_time(delayed_run_time), sequence_num(0),

[darin (slow to review), 2011/04/09 04:21:58]

nit: new line before sequence_num(0)

[awong, 2011/04/10 15:58:12]

Done.

+      nestable(nestable) {
+#if defined(TRACK_ALL_TASK_OBJECTS)
+    if (tracked_objects::ThreadData::IsActive()) {
+      tracked_objects::ThreadData* current_thread_data =
+          tracked_objects::ThreadData::current();
+      if (current_thread_data) {
+        post_births = current_thread_data->TallyABirth(posted_from);
+      } else {
+        // Shutdown started, and this thread wasn't registered.
+        post_births = NULL;
+      }
+    }
+#endif  // defined(TRACK_ALL_TASK_OBJECTS)
+  }
 
-bool MessageLoop::PendingTask::operator<(const PendingTask& other) const {
+bool MessageLoop::PendingClosure::operator<(const PendingClosure& other) const {
   // Since the top of a priority queue is defined as the "greatest" element, we
   // need to invert the comparison here.  We want the smaller time to be at the
   // top of the heap.