WebAudio: Split AudioNode::finishDeref into two parts.

Source/modules/webaudio/AudioNode.cpp

 /*
  * Copyright (C) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 37 matching lines @@
     , m_nodeType(NodeTypeUnknown)
     , m_context(context)
     , m_sampleRate(sampleRate)
 #if ENABLE(OILPAN)
     , m_keepAlive(adoptPtr(new Persistent<AudioNode>(this)))
 #endif
     , m_lastProcessingTime(-1)
     , m_lastNonSilentTime(-1)
     , m_normalRefCount(1) // start out with normal refCount == 1 (like WTF::RefCounted class)
     , m_connectionRefCount(0)
-    , m_wasDisconnected(false)
     , m_isMarkedForDeletion(false)
     , m_isDisabled(false)
     , m_channelCount(2)
     , m_channelCountMode(Max)
     , m_channelInterpretation(AudioBus::Speakers)
 {
     ScriptWrappable::init(this);
 #if DEBUG_AUDIONODE_REFERENCES
     if (!s_isNodeCountInitialized) {
         s_isNodeCountInitialized = true;
@@ skipping 451 matching lines @@
 
     // Once AudioContext::uninitialize() is called there's no more chances for deleteMarkedNodes() to get called, so we call here.
     // We can't call in AudioContext::~AudioContext() since it will never be called as long as any AudioNode is alive
     // because AudioNodes keep a reference to the context.
     if (!context()->isInitialized())
         context()->deleteMarkedNodes();
 }
 
 void AudioNode::breakConnection()
 {
+    // The actually work for deref happens completely within the audio context's

[Raymond Toy, 2014/07/14 16:43:01]

Typo: "actually" -> "actual"

[tkent, 2014/07/15 01:19:23]

Done.  Also fixed it in deref().

+    // graph lock. In the case of the audio thread, we must use a tryLock to
+    // avoid glitches.
+    bool hasLock = false;
+    bool mustReleaseLock = false;
+
+    if (context()->isAudioThread()) {
+        // Real-time audio thread must not contend lock (to avoid glitches).
+        hasLock = context()->tryLock(mustReleaseLock);
+    } else {
+        context()->lock(mustReleaseLock);
+        hasLock = true;
+    }
+
+    if (hasLock) {
+        breakConnectionWithLock();
+
+        if (mustReleaseLock)
+            context()->unlock();
+    } else {
+        // We were unable to get the lock, so put this in a list to finish up
+        // later.
+        ASSERT(context()->isAudioThread());
+        context()->addDeferredBreakConnection(*this);
+    }
+}
+
+void AudioNode::breakConnectionWithLock()
+{
     ASSERT(m_normalRefCount > 0);
     atomicDecrement(&m_connectionRefCount);
-    m_wasDisconnected = true;
+    if (m_connectionRefCount == 0 && m_normalRefCount > 1)
+        disableOutputsIfNecessary();
 }
 
 void AudioNode::finishDeref()
 {
     ASSERT(context()->isGraphOwner());
 
     ASSERT(m_normalRefCount > 0);
     atomicDecrement(&m_normalRefCount);
 
 #if DEBUG_AUDIONODE_REFERENCES
     fprintf(stderr, "%p: %d: AudioNode::deref() %d %d\n", this, nodeType(), m_normalRefCount, m_connectionRefCount);
 #endif
 
-    if (m_wasDisconnected) {
-        if (m_connectionRefCount == 0 && m_normalRefCount > 0)
-            disableOutputsIfNecessary();
-        m_wasDisconnected = false;
-    }
-
     if (!m_normalRefCount && !m_isMarkedForDeletion) {
         // All references are gone - we need to go away.
         for (unsigned i = 0; i < m_outputs.size(); ++i)
             output(i)->disconnectAll(); // This will deref() nodes we're connected to.
 
         // Mark for deletion at end of each render quantum or when context shuts
         // down.
         context()->markForDeletion(this);
         m_isMarkedForDeletion = true;
     }
@@ skipping 34 matching lines @@
     // it cannot be reattached. Therefore, the reference count
     // will not go above zero again.
     ASSERT(m_keepAlive);
     m_keepAlive = nullptr;
 }
 #endif
 
 } // namespace WebCore
 
 #endif // ENABLE(WEB_AUDIO)