Protect AudioScheduledSoureNode::m_startTime and m_endTime.

Source/modules/webaudio/OscillatorNode.cpp

 /*
  * Copyright (C) 2012, 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 208 matching lines @@
         outputBus->zero();
         return;
     }
 
     ASSERT(framesToProcess <= m_phaseIncrements.size());
     if (framesToProcess > m_phaseIncrements.size())
         return;
 
     // The audio thread can't block on this lock, so we call tryLock() instead.
     MutexTryLocker tryLocker(m_processLock);
-    if (!tryLocker.locked()) {
-        // Too bad - the tryLock() failed. We must be in the middle of changing wave-tables.
+    if (tryLocker.locked()) {
+

[tkent, 2015/09/11 00:02:00]

Is this change necessary?  The scope of tryLocker isn't changed.

+        // We must access m_periodicWave only inside the lock.
+        if (!m_periodicWave.get()) {
+            outputBus->zero();
+            return;
+        }
+
+        size_t quantumFrameOffset;
+        size_t nonSilentFramesToProcess;
+
+        updateSchedulingInfo(framesToProcess, outputBus, quantumFrameOffset, nonSilentFramesToProcess);
+
+        if (!nonSilentFramesToProcess) {
+            outputBus->zero();
+            return;
+        }
+
+        unsigned periodicWaveSize = m_periodicWave->periodicWaveSize();
+        double invPeriodicWaveSize = 1.0 / periodicWaveSize;
+
+        float* destP = outputBus->channel(0)->mutableData();
+
+        ASSERT(quantumFrameOffset <= framesToProcess);
+
+        // We keep virtualReadIndex double-precision since we're accumulating values.
+        double virtualReadIndex = m_virtualReadIndex;
+
+        float rateScale = m_periodicWave->rateScale();
+        float invRateScale = 1 / rateScale;
+        bool hasSampleAccurateValues = calculateSampleAccuratePhaseIncrements(framesToProcess);
+
+        float frequency = 0;
+        float* higherWaveData = 0;
+        float* lowerWaveData = 0;
+        float tableInterpolationFactor = 0;
+
+        if (!hasSampleAccurateValues) {
+            frequency = m_frequency->smoothedValue();
+            float detune = m_detune->smoothedValue();
+            float detuneScale = powf(2, detune / 1200);
+            frequency *= detuneScale;
+            m_periodicWave->waveDataForFundamentalFrequency(frequency, lowerWaveData, higherWaveData, tableInterpolationFactor);
+        }
+
+        float incr = frequency * rateScale;
+        float* phaseIncrements = m_phaseIncrements.data();
+
+        unsigned readIndexMask = periodicWaveSize - 1;
+
+        // Start rendering at the correct offset.
+        destP += quantumFrameOffset;
+        int n = nonSilentFramesToProcess;
+
+        while (n--) {
+            unsigned readIndex = static_cast<unsigned>(virtualReadIndex);
+            unsigned readIndex2 = readIndex + 1;
+
+            // Contain within valid range.
+            readIndex = readIndex & readIndexMask;
+            readIndex2 = readIndex2 & readIndexMask;
+
+            if (hasSampleAccurateValues) {
+                incr = *phaseIncrements++;
+
+                frequency = invRateScale * incr;
+                m_periodicWave->waveDataForFundamentalFrequency(frequency, lowerWaveData, higherWaveData, tableInterpolationFactor);
+            }
+
+            float sample1Lower = lowerWaveData[readIndex];
+            float sample2Lower = lowerWaveData[readIndex2];
+            float sample1Higher = higherWaveData[readIndex];
+            float sample2Higher = higherWaveData[readIndex2];
+
+            // Linearly interpolate within each table (lower and higher).
+            float interpolationFactor = static_cast<float>(virtualReadIndex) - readIndex;
+            float sampleHigher = (1 - interpolationFactor) * sample1Higher + interpolationFactor * sample2Higher;
+            float sampleLower = (1 - interpolationFactor) * sample1Lower + interpolationFactor * sample2Lower;
+
+            // Then interpolate between the two tables.
+            float sample = (1 - tableInterpolationFactor) * sampleHigher + tableInterpolationFactor * sampleLower;
+
+            *destP++ = sample;
+
+            // Increment virtual read index and wrap virtualReadIndex into the range 0 -> periodicWaveSize.
+            virtualReadIndex += incr;
+            virtualReadIndex -= floor(virtualReadIndex * invPeriodicWaveSize) * periodicWaveSize;
+        }
+
+        m_virtualReadIndex = virtualReadIndex;
+
+        outputBus->clearSilentFlag();
+    } else {
+        // Too bad - the tryLock() failed. We must be in the middle of changing wave-tables or
+        // updating scheduling.
         outputBus->zero();
         return;
     }
-
-    // We must access m_periodicWave only inside the lock.
-    if (!m_periodicWave.get()) {
-        outputBus->zero();
-        return;
-    }
-
-    size_t quantumFrameOffset;
-    size_t nonSilentFramesToProcess;
-
-    updateSchedulingInfo(framesToProcess, outputBus, quantumFrameOffset, nonSilentFramesToProcess);
-
-    if (!nonSilentFramesToProcess) {
-        outputBus->zero();
-        return;
-    }
-
-    unsigned periodicWaveSize = m_periodicWave->periodicWaveSize();
-    double invPeriodicWaveSize = 1.0 / periodicWaveSize;
-
-    float* destP = outputBus->channel(0)->mutableData();
-
-    ASSERT(quantumFrameOffset <= framesToProcess);
-
-    // We keep virtualReadIndex double-precision since we're accumulating values.
-    double virtualReadIndex = m_virtualReadIndex;
-
-    float rateScale = m_periodicWave->rateScale();
-    float invRateScale = 1 / rateScale;
-    bool hasSampleAccurateValues = calculateSampleAccuratePhaseIncrements(framesToProcess);
-
-    float frequency = 0;
-    float* higherWaveData = 0;
-    float* lowerWaveData = 0;
-    float tableInterpolationFactor = 0;
-
-    if (!hasSampleAccurateValues) {
-        frequency = m_frequency->smoothedValue();
-        float detune = m_detune->smoothedValue();
-        float detuneScale = powf(2, detune / 1200);
-        frequency *= detuneScale;
-        m_periodicWave->waveDataForFundamentalFrequency(frequency, lowerWaveData, higherWaveData, tableInterpolationFactor);
-    }
-
-    float incr = frequency * rateScale;
-    float* phaseIncrements = m_phaseIncrements.data();
-
-    unsigned readIndexMask = periodicWaveSize - 1;
-
-    // Start rendering at the correct offset.
-    destP += quantumFrameOffset;
-    int n = nonSilentFramesToProcess;
-
-    while (n--) {
-        unsigned readIndex = static_cast<unsigned>(virtualReadIndex);
-        unsigned readIndex2 = readIndex + 1;
-
-        // Contain within valid range.
-        readIndex = readIndex & readIndexMask;
-        readIndex2 = readIndex2 & readIndexMask;
-
-        if (hasSampleAccurateValues) {
-            incr = *phaseIncrements++;
-
-            frequency = invRateScale * incr;
-            m_periodicWave->waveDataForFundamentalFrequency(frequency, lowerWaveData, higherWaveData, tableInterpolationFactor);
-        }
-
-        float sample1Lower = lowerWaveData[readIndex];
-        float sample2Lower = lowerWaveData[readIndex2];
-        float sample1Higher = higherWaveData[readIndex];
-        float sample2Higher = higherWaveData[readIndex2];
-
-        // Linearly interpolate within each table (lower and higher).
-        float interpolationFactor = static_cast<float>(virtualReadIndex) - readIndex;
-        float sampleHigher = (1 - interpolationFactor) * sample1Higher + interpolationFactor * sample2Higher;
-        float sampleLower = (1 - interpolationFactor) * sample1Lower + interpolationFactor * sample2Lower;
-
-        // Then interpolate between the two tables.
-        float sample = (1 - tableInterpolationFactor) * sampleHigher + tableInterpolationFactor * sampleLower;
-
-        *destP++ = sample;
-
-        // Increment virtual read index and wrap virtualReadIndex into the range 0 -> periodicWaveSize.
-        virtualReadIndex += incr;
-        virtualReadIndex -= floor(virtualReadIndex * invPeriodicWaveSize) * periodicWaveSize;
-    }
-
-    m_virtualReadIndex = virtualReadIndex;
-
-    outputBus->clearSilentFlag();
 }
 
 void OscillatorHandler::setPeriodicWave(PeriodicWave* periodicWave)
 {
     ASSERT(isMainThread());
 
     // This synchronizes with process().
     MutexLocker processLocker(m_processLock);
     m_periodicWave = periodicWave;
     m_type = CUSTOM;
@@ skipping 54 matching lines @@
 }
 
 void OscillatorNode::setPeriodicWave(PeriodicWave* wave)
 {
     oscillatorHandler().setPeriodicWave(wave);
 }
 
 } // namespace blink
 
 #endif // ENABLE(WEB_AUDIO)