From ca88a23260a93b040549871088372193146566bc Mon Sep 17 00:00:00 2001
From: Matt Woodrow <mwoodrow@mozilla.com>
Date: Tue, 4 Nov 2014 11:16:34 +1300
Subject: [PATCH] Bug 1062661 - Part 1: Discard decoders that don't have any
 data in them. r=karlt

---
 dom/media/MediaDecoderReader.h        | 12 +++--
 dom/media/mediasource/TrackBuffer.cpp | 65 +++++++++++++++++++++++----
 2 files changed, 65 insertions(+), 12 deletions(-)

diff --git a/dom/media/MediaDecoderReader.h b/dom/media/MediaDecoderReader.h
index 576539680d9..4341b7056e9 100644
--- a/dom/media/MediaDecoderReader.h
+++ b/dom/media/MediaDecoderReader.h
@@ -180,6 +180,14 @@ public:
   // ReadMetada should be called before calling this method.
   virtual bool IsMediaSeekable() = 0;
 
+  MediaTaskQueue* GetTaskQueue() {
+    return mTaskQueue;
+  }
+
+  void ClearDecoder() {
+    mDecoder = nullptr;
+  }
+
 protected:
   virtual ~MediaDecoderReader();
 
@@ -206,10 +214,6 @@ protected:
     return mSampleDecodedCallback;
   }
 
-  virtual MediaTaskQueue* GetTaskQueue() {
-    return mTaskQueue;
-  }
-
   // Queue of audio frames. This queue is threadsafe, and is accessed from
   // the audio, decoder, state machine, and main threads.
   MediaQueue<AudioData> mAudioQueue;
diff --git a/dom/media/mediasource/TrackBuffer.cpp b/dom/media/mediasource/TrackBuffer.cpp
index f8e2a40fa42..32e0d4b9ba0 100644
--- a/dom/media/mediasource/TrackBuffer.cpp
+++ b/dom/media/mediasource/TrackBuffer.cpp
@@ -59,6 +59,7 @@ public:
   }
 
   NS_IMETHOD Run() MOZ_OVERRIDE MOZ_FINAL {
+    mDecoder->GetReader()->BreakCycles();
     mDecoder = nullptr;
     return NS_OK;
   }
@@ -155,6 +156,7 @@ bool
 TrackBuffer::EvictData(uint32_t aThreshold)
 {
   MOZ_ASSERT(NS_IsMainThread());
+  ReentrantMonitorAutoEnter mon(mParentDecoder->GetReentrantMonitor());
 
   int64_t totalSize = 0;
   for (uint32_t i = 0; i < mDecoders.Length(); ++i) {
@@ -166,10 +168,14 @@ TrackBuffer::EvictData(uint32_t aThreshold)
     return false;
   }
 
-  for (uint32_t i = 0; i < mDecoders.Length(); ++i) {
+  for (uint32_t i = 0; i < mInitializedDecoders.Length(); ++i) {
     MSE_DEBUG("TrackBuffer(%p)::EvictData decoder=%u threshold=%u toEvict=%lld",
               this, i, aThreshold, toEvict);
-    toEvict -= mDecoders[i]->GetResource()->EvictData(toEvict);
+    toEvict -= mInitializedDecoders[i]->GetResource()->EvictData(toEvict);
+    if (!mInitializedDecoders[i]->GetResource()->GetSize() &&
+        mInitializedDecoders[i] != mCurrentDecoder) {
+      RemoveDecoder(mInitializedDecoders[i]);
+    }
   }
   return toEvict < (totalSize - aThreshold);
 }
@@ -178,11 +184,16 @@ void
 TrackBuffer::EvictBefore(double aTime)
 {
   MOZ_ASSERT(NS_IsMainThread());
-  for (uint32_t i = 0; i < mDecoders.Length(); ++i) {
-    int64_t endOffset = mDecoders[i]->ConvertToByteOffset(aTime);
+  ReentrantMonitorAutoEnter mon(mParentDecoder->GetReentrantMonitor());
+  for (uint32_t i = 0; i < mInitializedDecoders.Length(); ++i) {
+    int64_t endOffset = mInitializedDecoders[i]->ConvertToByteOffset(aTime);
     if (endOffset > 0) {
       MSE_DEBUG("TrackBuffer(%p)::EvictBefore decoder=%u offset=%lld", this, i, endOffset);
-      mDecoders[i]->GetResource()->EvictBefore(endOffset);
+      mInitializedDecoders[i]->GetResource()->EvictBefore(endOffset);
+      if (!mInitializedDecoders[i]->GetResource()->GetSize() &&
+          mInitializedDecoders[i] != mCurrentDecoder) {
+        RemoveDecoder(mInitializedDecoders[i]);
+      }
     }
   }
 }
@@ -458,20 +469,58 @@ TrackBuffer::Dump(const char* aPath)
 }
 #endif
 
+class DelayedDispatchToMainThread : public nsRunnable {
+public:
+  explicit DelayedDispatchToMainThread(SourceBufferDecoder* aDecoder)
+    : mDecoder(aDecoder)
+  {
+  }
+
+  NS_IMETHOD Run() MOZ_OVERRIDE MOZ_FINAL {
+    // Shutdown the reader, and remove its reference to the decoder
+    // so that it can't accidentally read it after the decoder
+    // is destroyed.
+    mDecoder->GetReader()->Shutdown();
+    mDecoder->GetReader()->ClearDecoder();
+    RefPtr<nsIRunnable> task = new ReleaseDecoderTask(mDecoder);
+    mDecoder = nullptr;
+    // task now holds the only ref to the decoder.
+    NS_DispatchToMainThread(task);
+    return NS_OK;
+  }
+
+private:
+  RefPtr<SourceBufferDecoder> mDecoder;
+};
+
 void
 TrackBuffer::RemoveDecoder(SourceBufferDecoder* aDecoder)
 {
-  RefPtr<nsIRunnable> task = new ReleaseDecoderTask(aDecoder);
+  RefPtr<nsIRunnable> task;
+  nsRefPtr<MediaTaskQueue> taskQueue;
   {
     ReentrantMonitorAutoEnter mon(mParentDecoder->GetReentrantMonitor());
-    MOZ_ASSERT(!mInitializedDecoders.Contains(aDecoder));
+    if (mInitializedDecoders.RemoveElement(aDecoder)) {
+      taskQueue = aDecoder->GetReader()->GetTaskQueue();
+      task = new DelayedDispatchToMainThread(aDecoder);
+    } else {
+      task = new ReleaseDecoderTask(aDecoder);
+    }
     mDecoders.RemoveElement(aDecoder);
+
     if (mCurrentDecoder == aDecoder) {
       DiscardDecoder();
     }
   }
   // At this point, task should be holding the only reference to aDecoder.
-  NS_DispatchToMainThread(task);
+  if (taskQueue) {
+    // If we were initialized, post the task via the reader's
+    // task queue to ensure that the reader isn't in the middle
+    // of an existing task.
+    taskQueue->Dispatch(task);
+  } else {
+    NS_DispatchToMainThread(task);
+  }
 }
 
 } // namespace mozilla