DetachFromSequence in Timer::Stop()

base/timer/timer.cc

 // 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.
 
 #include "base/timer/timer.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 81 matching lines @@
       user_task_(user_task),
       is_repeating_(is_repeating),
       retain_user_task_(true),
       tick_clock_(tick_clock),
       is_running_(false) {
   // See comment in other constructor.
   origin_sequence_checker_.DetachFromSequence();
 }
 
 Timer::~Timer() {
-  // TODO(gab): Enable this once Stop() properly detaches from sequence.
-  // DCHECK(origin_sequence_checker_.CalledOnValidSequence());
+  DCHECK(origin_sequence_checker_.CalledOnValidSequence());
   AbandonAndStop();
 }
 
 bool Timer::IsRunning() const {
   DCHECK(origin_sequence_checker_.CalledOnValidSequence());
   return is_running_;
 }
 
 TimeDelta Timer::GetCurrentDelay() const {
   DCHECK(origin_sequence_checker_.CalledOnValidSequence());
@@ skipping 23 matching lines @@
 
   Reset();
 }
 
 void Timer::Stop() {
   // TODO(gab): Enable this when it's no longer called racily from
   // RunScheduledTask(): https://crbug.com/587199.
   // DCHECK(origin_sequence_checker_.CalledOnValidSequence());
 
   is_running_ = false;
+
+  // It's safe to destroy or restart Timer on another sequence after Stop().

[danakj, 2017/06/06 20:07:12]

Did you intentionally do this before running the user_task_ destructors?

[gab, 2017/06/07 13:28:54]

Yes, see comment at the end of this method, it's not safe to access |this| after
destroying |user_task_| as it can own |this|.

+  origin_sequence_checker_.DetachFromSequence();
+
   if (!retain_user_task_)
     user_task_.Reset();
   // No more member accesses here: |this| could be deleted after freeing
   // |user_task_|.
 }
 
 void Timer::Reset() {
   DCHECK(origin_sequence_checker_.CalledOnValidSequence());
   DCHECK(!user_task_.is_null());
 
@@ skipping 97 matching lines @@
     PostNewScheduledTask(delay_);
   else
     Stop();
 
   task.Run();
 
   // No more member accesses here: |this| could be deleted at this point.
 }
 
 }  // namespace base