From cdf6c332a6b347eea32eeb645f5ae031edafac0c Mon Sep 17 00:00:00 2001
From: Zach Pomerantz <zmp@umich.edu>
Date: Fri, 5 May 2017 15:42:22 -0400
Subject: [PATCH] prevent overflow of local injectors buffer

---
 libraries/audio-client/src/AudioClient.cpp | 32 +++++++++++-----------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/libraries/audio-client/src/AudioClient.cpp b/libraries/audio-client/src/AudioClient.cpp
index fb0220c24d..f61429812f 100644
--- a/libraries/audio-client/src/AudioClient.cpp
+++ b/libraries/audio-client/src/AudioClient.cpp
@@ -1097,26 +1097,26 @@ void AudioClient::handleRecordedAudioInput(const QByteArray& audio) {
 }
 
 void AudioClient::prepareLocalAudioInjectors() {
-    if (_outputPeriod == 0) {
-        return;
-    }
-
-    int bufferCapacity = _localInjectorsStream.getSampleCapacity();
-    if (_localToOutputResampler) {
-        // avoid overwriting the buffer,
-        // instead of failing on writes because the buffer is used as a lock-free pipe
-        bufferCapacity -=
-            _localToOutputResampler->getMaxOutput(AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL) *
-            AudioConstants::STEREO;
-        bufferCapacity += 1;
-    }
-
     int samplesNeeded = std::numeric_limits<int>::max();
     while (samplesNeeded > 0) {
-        // lock for every write to avoid locking out the device callback
-        // this lock is intentional - the buffer is only lock-free in its use in the device callback
+        // unlock between every write to allow device switching
         Lock lock(_localAudioMutex);
 
+        // in case of a device switch, consider bufferCapacity volatile across iterations
+        if (_outputPeriod == 0) {
+            return;
+        }
+
+        int bufferCapacity = _localInjectorsStream.getSampleCapacity();
+        if (_localToOutputResampler) {
+            // avoid overwriting the buffer,
+            // instead of failing on writes because the buffer is used as a lock-free pipe
+            bufferCapacity -=
+                _localToOutputResampler->getMaxOutput(AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL) *
+                AudioConstants::STEREO;
+            bufferCapacity += 1;
+        }
+
         samplesNeeded = bufferCapacity - _localSamplesAvailable.load(std::memory_order_relaxed);
         if (samplesNeeded <= 0) {
             break;