cpp/openttd-patchpack/source Changeset - r26535:bbf17c1357f1

Changeset - r26535:bbf17c1357f1

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Jonathan G Rennison - 22 months ago 2022-11-07 21:19:06
j.g.rennison@gmail.com

Fix: Data races on MixerChannel active states

1 file changed with 24 insertions and 24 deletions:

src/mixer.cpp

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src/mixer.cpp

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@@ @@ -7,22 +7,21 @@ @@
 /** @file mixer.cpp Mixing of sound samples. */
 #include "stdafx.h"
 #include <math.h>
 #include <mutex>
 #include <atomic>
 #include "core/math_func.hpp"
 #include "framerate_type.h"
 #include "settings_type.h"
 #include "safeguards.h"
 #include "mixer.h"
 struct MixerChannel {
 	bool active;
 	/* pointer to allocated buffer memory */
 	int8 *memory;
 	/* current position in memory */
 	uint32 pos;
 	uint32 frac_pos;
@@ @@ -33,12 +32,13 @@ struct MixerChannel { @@
 	int volume_left;
 	int volume_right;
 	bool is16bit;
 };
 static std::atomic<uint8> _active_channels;
 static MixerChannel _channels[8];
 static uint32 _play_rate = 11025;
 static uint32 _max_size = UINT_MAX;
 static MxStreamCallback _music_stream = nullptr;
 static std::mutex _music_stream_mutex;
@@ @@ -132,28 +132,26 @@ static void mix_int8_to_int16(MixerChann @@
+	}
 	sc->frac_pos = frac_pos;
 	sc->pos = b - sc->memory;
+}
-static void MxCloseChannel(MixerChannel *mc)
+static void MxCloseChannel(uint8 channel_index)
+{
-	mc->active = false;
+	_active_channels.fetch_and(~(1 << channel_index), std::memory_order_release);
+}
 void MxMixSamples(void *buffer, uint samples)
+{
 	PerformanceMeasurer framerate(PFE_SOUND);
 	static uint last_samples = 0;
 	if (samples != last_samples) {
 		framerate.SetExpectedRate((double)_play_rate / samples);
 		last_samples = samples;
+	}
 	MixerChannel *mc;
 	/* Clear the buffer */
 	memset(buffer, 0, sizeof(int16) * 2 * samples);
+	{
 		std::lock_guard<std::mutex> lock{ _music_stream_mutex };
 		/* Fetch music if a sampled stream is available */
@@ @@ -166,35 +164,36 @@ void MxMixSamples(void *buffer, uint sam @@
 	 * get back into range. */
 	uint8 effect_vol = (_settings_client.music.effect_vol *
 	                    _settings_client.music.effect_vol *
 	                    _settings_client.music.effect_vol) / (127 * 127);
 	/* Mix each channel */
 	for (mc = _channels; mc != endof(_channels); mc++) {
 		if (mc->active) {
 			if (mc->is16bit) {
 				mix_int16(mc, (int16*)buffer, samples, effect_vol);
 			} else {
 				mix_int8_to_int16(mc, (int16*)buffer, samples, effect_vol);
+			}
 			if (mc->samples_left == 0) MxCloseChannel(mc);
 	uint8 active = _active_channels.load(std::memory_order_acquire);
 	for (uint8 idx : SetBitIterator(active)) {
 		MixerChannel *mc = &_channels[idx];
 		if (mc->is16bit) {
 			mix_int16(mc, (int16*)buffer, samples, effect_vol);
 		} else {
 			mix_int8_to_int16(mc, (int16*)buffer, samples, effect_vol);
+		}
 		if (mc->samples_left == 0) MxCloseChannel(idx);
+	}
+}
 MixerChannel *MxAllocateChannel()
+{
 	MixerChannel *mc;
 	for (mc = _channels; mc != endof(_channels); mc++) {
 		if (!mc->active) {
 			free(mc->memory);
 			mc->memory = nullptr;
 			return mc;
+		}
+	}
 	return nullptr;
 	uint8 currently_active = _active_channels.load(std::memory_order_acquire);
 	uint8 available = ~currently_active;
 	if (available == 0) return nullptr;
 	uint8 channel_index = FindFirstBit(available);
 	MixerChannel *mc = &_channels[channel_index];
 	free(mc->memory);
 	mc->memory = nullptr;
 	return mc;
+}
 void MxSetChannelRawSrc(MixerChannel *mc, int8 *mem, size_t size, uint rate, bool is16bit)
+{
 	mc->memory = mem;
 	mc->frac_pos = 0;
@@ @@ -228,13 +227,14 @@ void MxSetChannelVolume(MixerChannel *mc @@
 	mc->volume_right = (uint)(sin(pan * M_PI / 2.0) * volume);
+}
 void MxActivateChannel(MixerChannel *mc)
+{
 	mc->active = true;
 	uint8 channel_index = mc - _channels;
 	_active_channels.fetch_or((1 << channel_index), std::memory_order_release);
+}
 /**
  * Set source of PCM music
  * @param music_callback Function that will be called to fill sample buffers with music data.
  * @return Sample rate of mixer, which the buffers supplied to the callback must be rendered at.

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