Fix threading races on AudioDSPKernelProcessor::m_kernels

Source/core/platform/audio/AudioDSPKernelProcessor.cpp

Index: Source/core/platform/audio/AudioDSPKernelProcessor.cpp
diff --git a/Source/core/platform/audio/AudioDSPKernelProcessor.cpp b/Source/core/platform/audio/AudioDSPKernelProcessor.cpp
index 0875464968f0ca5e4b05204984eafa73a8117d15..5a8c20f7adb4dff01cba23060d7f7ac3783bd2c2 100644
--- a/Source/core/platform/audio/AudioDSPKernelProcessor.cpp
+++ b/Source/core/platform/audio/AudioDSPKernelProcessor.cpp
@@ -50,6 +50,7 @@ void AudioDSPKernelProcessor::initialize()
     if (isInitialized())
         return;
 
+    MutexLocker locker(m_processLock);
     ASSERT(!m_kernels.size());
 
     // Create processing kernels, one per channel.
@@ -65,6 +66,7 @@ void AudioDSPKernelProcessor::uninitialize()
     if (!isInitialized())
         return;
 
+    MutexLocker locker(m_processLock);
     m_kernels.clear();
 
     m_initialized = false;
@@ -81,13 +83,20 @@ void AudioDSPKernelProcessor::process(const AudioBus* source, AudioBus* destinat
         return;
     }
 
-    bool channelCountMatches = source->numberOfChannels() == destination->numberOfChannels() && source->numberOfChannels() == m_kernels.size();
-    ASSERT(channelCountMatches);
-    if (!channelCountMatches)
-        return;
-
-    for (unsigned i = 0; i < m_kernels.size(); ++i)
-        m_kernels[i]->process(source->channel(i)->data(), destination->channel(i)->mutableData(), framesToProcess);
+    MutexTryLocker tryLocker(m_processLock);
+    if (tryLocker.locked()) {
+        bool channelCountMatches = source->numberOfChannels() == destination->numberOfChannels() && source->numberOfChannels() == m_kernels.size();
+        ASSERT(channelCountMatches);
+        if (!channelCountMatches)
+            return;
+
+        for (unsigned i = 0; i < m_kernels.size(); ++i)
+            m_kernels[i]->process(source->channel(i)->data(), destination->channel(i)->mutableData(), framesToProcess);
+    } else {
+        // Unfortunately, the kernel is being processed by another thread.
+        // See also ConvolverNode::process().
+        destination->zero();
+    }
 }
 
 // Resets filter state
@@ -100,6 +109,7 @@ void AudioDSPKernelProcessor::reset()
     // Any processing depending on this value must set it to false at the appropriate time.
     m_hasJustReset = true;
 
+    MutexLocker locker(m_processLock);
     for (unsigned i = 0; i < m_kernels.size(); ++i)
         m_kernels[i]->reset();
 }
@@ -116,12 +126,14 @@ void AudioDSPKernelProcessor::setNumberOfChannels(unsigned numberOfChannels)
 
 double AudioDSPKernelProcessor::tailTime() const
 {
+    MutexLocker locker(m_processLock);

[Ken Russell (switch to Gerrit), 2013/09/04 18:18:46]

I believe this is called on the audio thread and therefore must use a trylock.

Please add an assertion like ASSERT(context()->isAudioThread()).

[haraken, 2013/09/04 19:50:05]

Done.

     // It is expected that all the kernels have the same tailTime.
     return !m_kernels.isEmpty() ? m_kernels.first()->tailTime() : 0;
 }
 
 double AudioDSPKernelProcessor::latencyTime() const
 {
+    MutexLocker locker(m_processLock);

[Ken Russell (switch to Gerrit), 2013/09/04 18:18:46]

trylock needed here too.

[haraken, 2013/09/04 19:50:05]

Done.

     // It is expected that all the kernels have the same latencyTime.
     return !m_kernels.isEmpty() ? m_kernels.first()->latencyTime() : 0;
 }