Remote assistance on Chrome OS Part IV - It2MeHost

remoting/base/auto_thread.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 "remoting/base/auto_thread.h"
 
 #include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
 #include "base/threading/thread_local.h"
@@ skipping 95 matching lines @@
     name_(name),
     was_quit_properly_(false),
     joiner_(joiner) {
 }
 
 AutoThread::~AutoThread() {
   DCHECK(!startup_data_);
 
   // Wait for the thread to exit.
   if (!thread_.is_null()) {
+    // AutoThread only destroys itself when there are no outstanding references
+    // to its task runner. Therefore it is guaranteed that the join is
+    // non-blocking as its task runner will always be empty at shutdown.

[Wez, 2014/10/17 17:57:59]

This guarantee actually doesn't hold if you do the ScopedAllowIO here, since a
caller can create an AutoThread and manage its lifetime manually, in which case
this Join() _can_ block.

The guarantee only holds in JoinAndDeleteThread(), so the ScopedAllowIO should
be there.

[kelvinp, 2014/10/20 00:21:16]

Done.

+    base::ThreadRestrictions::ScopedAllowIO allow_io;

[Wez, 2014/10/17 17:57:59]

I'd recommend making this change in a separate CL, since IIRC you'll need a
special approval from a base::Thread owner for adding another use of
ScopedAllowIO.

[kelvinp, 2014/10/20 00:21:16]

I have already added jam on this CL.

     base::PlatformThread::Join(thread_);
   }
 }
 
 scoped_refptr<AutoThreadTaskRunner> AutoThread::StartWithType(
     base::MessageLoop::Type type) {
   DCHECK(thread_.is_null());
 #if defined(OS_WIN)
   DCHECK(com_init_type_ != COM_INIT_STA || type == base::MessageLoop::TYPE_UI);
 #endif
@@ skipping 79 matching lines @@
       CreateComInitializer(com_init_type_));
 #endif
 
   message_loop.Run();
 
   // Assert that MessageLoop::Quit was called by AutoThread::QuitThread.
   DCHECK(was_quit_properly_);
 }
 
 }  // namespace base