Fix ChunkDemuxer seek deadlock

media/filters/audio_renderer_base.cc

Index: media/filters/audio_renderer_base.cc
diff --git a/media/filters/audio_renderer_base.cc b/media/filters/audio_renderer_base.cc
index 049a39a1005856fc38032ddc3da4b879636bccf5..d40bac46460968419b4f48408fa78501fdefbd25 100644
--- a/media/filters/audio_renderer_base.cc
+++ b/media/filters/audio_renderer_base.cc
@@ -67,6 +67,7 @@ void AudioRendererBase::Seek(base::TimeDelta time, const FilterStatusCB& cb) {
   base::AutoLock auto_lock(lock_);
   DCHECK_EQ(kPaused, state_);
   DCHECK(!pending_read_) << "Pending read must complete before seeking";
+  DCHECK(pause_callback_.is_null());
   DCHECK(seek_cb_.is_null());
   state_ = kSeeking;
   seek_cb_ = cb;
@@ -151,30 +152,35 @@ void AudioRendererBase::DecodedAudioReady(scoped_refptr<Buffer> buffer) {
     return;
   }
 
-  // Don't enqueue an end-of-stream buffer because it has no data, otherwise
-  // discard decoded audio data until we reach our desired seek timestamp.
-  if (buffer->IsEndOfStream()) {
-    recieved_end_of_stream_ = true;
-
-    // Transition to kPlaying if we are currently handling an underflow since no
-    // more data will be arriving.
-    if (state_ == kUnderflow || state_ == kRebuffering)
-      state_ = kPlaying;
-  } else if (state_ == kSeeking && !buffer->IsEndOfStream() &&
-             (buffer->GetTimestamp() + buffer->GetDuration()) <
-                 seek_timestamp_) {
-    ScheduleRead_Locked();
-  } else {
-    // Note: Calling this may schedule more reads.
-    algorithm_->EnqueueBuffer(buffer);
+  if (buffer) {

[Ami GONE FROM CHROMIUM, 2012/01/27 23:44:58]

that you can't reverse the test and early-return (b/c of the code from l.175
downwards) smells wrong.

I wonder whether this and the next big if block can be unified into a switch
(state).  Want to take a crack at it?

[acolwell GONE FROM CHROMIUM, 2012/01/29 03:00:41]

Done. Cleaned things up nicely and uncovered an unused state!

+    // Don't enqueue an end-of-stream buffer because it has no data, otherwise
+    // discard decoded audio data until we reach our desired seek timestamp.
+    if (buffer->IsEndOfStream()) {
+      recieved_end_of_stream_ = true;
+
+      // Transition to kPlaying if we are currently handling an underflow since
+      // no more data will be arriving.
+      if (state_ == kUnderflow || state_ == kRebuffering)
+        state_ = kPlaying;
+    } else if (state_ == kSeeking && !buffer->IsEndOfStream() &&
+               (buffer->GetTimestamp() + buffer->GetDuration()) <
+               seek_timestamp_) {
+      ScheduleRead_Locked();
+    } else {
+      // Note: Calling this may schedule more reads.
+      algorithm_->EnqueueBuffer(buffer);
+    }
   }
 
   // Check for our preroll complete condition.
   if (state_ == kSeeking) {
     DCHECK(!seek_cb_.is_null());
-    if (algorithm_->IsQueueFull() || recieved_end_of_stream_) {
-      // Transition into paused whether we have data in |algorithm_| or not.
-      // FillBuffer() will play silence if there's nothing to fill.
+
+    // Transition to paused if we have enough data or have reached the end of
+    // the stream. A NULL buffer also triggers the transition because it
+    // indicates that another seek will happen right after we complete this one
+    // so there is no point in continuing to preroll.
+    if (algorithm_->IsQueueFull() || recieved_end_of_stream_ || !buffer) {
       state_ = kPaused;
       ResetAndRunCB(&seek_cb_, PIPELINE_OK);
     }