Web MIDI: Add CHECK()s to ensure MidiManager owned threads are terminated

media/midi/midi_manager_alsa.cc

 // Copyright 2014 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 "media/midi/midi_manager_alsa.h"
 
 #include <errno.h>
 #include <poll.h>
 #include <stddef.h>
 #include <stdlib.h>
@@ skipping 140 matching lines @@
 }  // namespace
 
 MidiManagerAlsa::MidiManagerAlsa()
     : event_thread_("MidiEventThread"), send_thread_("MidiSendThread") {}
 
 MidiManagerAlsa::~MidiManagerAlsa() {
   // Take lock to ensure that the members initialized on the IO thread
   // are not destructed here.
   base::AutoLock lock(lazy_init_member_lock_);
 
   // Extra DCHECK to verify all members are already reset.

[Adam Goode, 2016/07/21 15:40:30]

You could change all the DCHECK to CHECK here.

[Takashi Toyoshima, 2016/07/25 05:38:00]

Done.

   DCHECK(!initialization_thread_checker_);
   DCHECK(!in_client_);
   DCHECK(!out_client_);
   DCHECK(!decoder_);
   DCHECK(!udev_);
   DCHECK(!udev_monitor_);
+
+  CHECK(!send_thread_.IsRunning());

[Adam Goode, 2016/07/21 15:40:30]

I don't think you can be sure of the result of IsRunning() if called from a
different thread than calls Start().

[Takashi Toyoshima, 2016/07/21 18:25:24]

IsRunning() is safe to be called from any thread.
Of course, Start() and Stop() could be called any time. But in our case, these
are called only on the IO thread in StartInitialization() and Finalize(), and
the IO thread stops before destructing MidiManager and BrowserMainLoop.

So this check works in practice.

+  CHECK(!event_thread_.IsRunning());
 }
 
 void MidiManagerAlsa::StartInitialization() {
   base::AutoLock lock(lazy_init_member_lock_);
 
   initialization_thread_checker_.reset(new base::ThreadChecker());
 
   // Create client handles.
   snd_seq_t* tmp_seq = nullptr;
   int err =
@@ skipping 1216 matching lines @@
   source_map_[AddrToInt(client_id, port_id)] = port_index;
   return true;
 }
 
 MidiManager* MidiManager::Create() {
   return new MidiManagerAlsa();
 }
 
 }  // namespace midi
 }  // namespace media