Revert CL 2242573002

third_party/WebKit/Source/modules/webaudio/BiquadProcessor.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 73 matching lines @@
     }
 }
 
 void BiquadProcessor::process(const AudioBus* source, AudioBus* destination, size_t framesToProcess)
 {
     if (!isInitialized()) {
         destination->zero();
         return;
     }
 
+    // Synchronize with possible dynamic changes to the impulse response.
+    MutexTryLocker tryLocker(m_processLock);
+    if (!tryLocker.locked()) {
+        // Can't get the lock. We must be in the middle of changing something.
+        destination->zero();
+        return;
+    }
+
     checkForDirtyCoefficients();
 
     // For each channel of our input, process using the corresponding BiquadDSPKernel into the output channel.
     for (unsigned i = 0; i < m_kernels.size(); ++i)
         m_kernels[i]->process(source->channel(i)->data(), destination->channel(i)->mutableData(), framesToProcess);
 }
 
 void BiquadProcessor::setType(FilterType type)
 {
     if (type != m_type) {
         m_type = type;
         reset(); // The filter state must be reset only if the type has changed.
     }
 }
 
 void BiquadProcessor::getFrequencyResponse(int nFrequencies, const float* frequencyHz, float* magResponse, float* phaseResponse)
 {
     // Compute the frequency response on a separate temporary kernel
     // to avoid interfering with the processing running in the audio
     // thread on the main kernels.
 
     std::unique_ptr<BiquadDSPKernel> responseKernel = wrapUnique(new BiquadDSPKernel(this));
     responseKernel->getFrequencyResponse(nFrequencies, frequencyHz, magResponse, phaseResponse);
 }
 
 } // namespace blink