AUDIO: (FM-TOWNS/PC-98) - fix regression from 0e734722

My commit 0e734722 causes lockups in SCUMM (sometimes) and SCI (very often). I didn't like the way I had fixed this before, but in the end I now had to do it in a similar way.

1 files changed, 10 insertions, 4 deletions

diff --git a/audio/softsynth/fmtowns_pc98/towns_pc98_fmsynth.cpp b/audio/softsynth/fmtowns_pc98/towns_pc98_fmsynth.cpp
index 558c389ebd..db81485426 100644
--- a/audio/softsynth/fmtowns_pc98/towns_pc98_fmsynth.cpp
+++ b/audio/softsynth/fmtowns_pc98/towns_pc98_fmsynth.cpp
@@ -963,7 +963,7 @@ TownsPC98_FmSynth::TownsPC98_FmSynth(Audio::Mixer *mixer, EmuType type) :
 	_samplesPerWaitCycle(type == kType26 ? 72 : 144),
 #endif
 	_outputRate(mixer->getOutputRate()), _rateScale(type == kType26 ? 0 : 1),
-	_volMaskA(0), _volMaskB(0), _volumeA(255), _volumeB(255), _ready(false) {
+	_volMaskA(0), _volMaskB(0), _volumeA(255), _volumeB(255), _mixerThreadLockCounter(0), _ready(false) {
 
 	memset(&_timers[0], 0, sizeof(ChipTimer));
 	memset(&_timers[1], 0, sizeof(ChipTimer));
@@ -1119,10 +1119,13 @@ uint8 TownsPC98_FmSynth::readReg(uint8 part, uint8 regAddress) {
 }
 
 int TownsPC98_FmSynth::readBuffer(int16 *buffer, const int numSamples) {
-	Common::StackLock lock(_mutex);
-	if (!_ready)
+	_mutex.lock();
+	if (!_ready) {
+		_mutex.unlock();
 		return 0;
-
+	}
+	_mixerThreadLockCounter++;
+	
 	// This assumes that the numSamples parameter will be the same on most (if not on all) calls to readBuffer(),
 	// although I don't know whether this is true for all backends. There is no need to reallocate the temp
 	// buffer every time, unless its size needs to be increased.
@@ -1236,6 +1239,9 @@ int TownsPC98_FmSynth::readBuffer(int16 *buffer, const int numSamples) {
 		_numPending = render + _numPending - consumed;
 	}
 
+	_mutex.unlock();
+	_mixerThreadLockCounter--;
+
 	return numSamples;
 }