Always wait for DataReady() on Windows WaveOut.

media/audio/audio_output_controller.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 "media/audio/audio_output_controller.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/message_loop.h"
 #include "base/synchronization/waitable_event.h"
@@ skipping 301 matching lines @@
     }
   }
 
   int frames = sync_reader_->Read(source, dest);
   sync_reader_->UpdatePendingBytes(
       buffers_state.total_bytes() + frames * params_.GetBytesPerFrame());
   return frames;
 }
 
 void AudioOutputController::WaitTillDataReady() {
-  if (!sync_reader_->DataReady()) {
-    // In the different place we use different mechanism to poll, get max
-    // polling delay from constants used there.
-    const base::TimeDelta kMaxPollingDelay = TimeDelta::FromMilliseconds(
-        kPollNumAttempts * kPollPauseInMilliseconds);
-    Time start_time = Time::Now();
-    do {
-      base::PlatformThread::Sleep(TimeDelta::FromMilliseconds(1));
-    } while (!sync_reader_->DataReady() &&
-             Time::Now() - start_time < kMaxPollingDelay);
-  }
+  while (!sync_reader_->DataReady())

[scherkus (not reviewing), 2012/11/21 21:37:57]

how about backing up your comments w/ something like

#if defined(OS_WIN)
...
#else
  CHECK(false) << "You didn't read the comment, did you?"
#endif

[DaleCurtis, 2012/11/21 22:42:10]

We'll need OS_MAC in there too for now since the high latency path uses this to
spool audio output buffers.  I left it out of the comment since we're planning
to remove that path in the future.

+    base::PlatformThread::YieldCurrentThread();

[Chris Rogers, 2012/11/21 19:33:37]

We should probably check that this while is not spinning for an unreasonable
amount of time to avoid potential infinite-loop / hang.
In other words, some kind of timeout to handle the case when for any reason (bug
or otherwise), the renderer gets into a condition where it's unable to *ever*
have data ready.

[scherkus (not reviewing), 2012/11/21 21:37:57]

perhaps a CHECK()-timeout and monitor for any reports?

[DaleCurtis, 2012/11/21 22:42:10]

CHECK() worries me, I've added a 1.5 second timeout for now.

 }
 
 void AudioOutputController::OnError(AudioOutputStream* stream, int code) {
   // Handle error on the audio controller thread.
   message_loop_->PostTask(FROM_HERE, base::Bind(
       &AudioOutputController::DoReportError, this, code));
 }
 
 void AudioOutputController::DoStopCloseAndClearStream(WaitableEvent* done) {
   DCHECK(message_loop_->BelongsToCurrentThread());
@@ skipping 43 matching lines @@
     case kPausedWhenStarting:
     case kPaused:
       // From the outside these three states are equivalent.
       return;
     default:
       NOTREACHED() << "Invalid original state.";
   }
 }
 
 }  // namespace media