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Don't busy wait in the audio thread (ALSA)

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When the emulation is paused and the ALSA backend is used, make the audio
thread wait on a condition variable instead of busy-waiting. This commit
fixes bug #7729

Since the ALSA API is not thread-safe, calls to snd_pcm_drop() and snd_pcm_prepare()
in AlsaSound::Clear() are protected by the same mutex as the condition variable in AlsaSound::SoundLoop()
to make sure that we do not call these functions while a call to
snd_pcm_writei() is ongoing.
This commit is contained in:
Moncef Mechri
2015-07-07 15:30:27 +02:00
parent a0c5247743
commit 333f998123
2 changed files with 33 additions and 1 deletions
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29
Source/Core/AudioCommon/AlsaSoundStream.cpp
View File

@ -2,6 +2,8 @@
// Licensed under GPLv2+
// Refer to the license.txt file included.
#include <mutex>
#include "AudioCommon/AlsaSoundStream.h"
#include "Common/CommonTypes.h"
#include "Common/Thread.h"
@ -39,6 +41,10 @@ bool AlsaSound::Start()
void AlsaSound::Stop()
{
m_thread_status.store(ALSAThreadStatus::STOPPING);
//Give the opportunity to the audio thread
//to realize we are stopping the emulation
cv.notify_one();
thread.join();
}
@ -53,8 +59,11 @@ void AlsaSound::SoundLoop()
Common::SetCurrentThreadName("Audio thread - alsa");
while (m_thread_status.load() == ALSAThreadStatus::RUNNING)
{
std::unique_lock<std::mutex> lock(cv_m);
cv.wait(lock, [this]{return !m_muted || m_thread_status.load() != ALSAThreadStatus::RUNNING;});
m_mixer->Mix(reinterpret_cast<short *>(mix_buffer), frames_to_deliver);
int rc = m_muted ? 1337 : snd_pcm_writei(handle, mix_buffer, frames_to_deliver);
int rc = snd_pcm_writei(handle, mix_buffer, frames_to_deliver);
if (rc == -EPIPE)
{
// Underrun
@ -69,6 +78,24 @@ void AlsaSound::SoundLoop()
m_thread_status.store(ALSAThreadStatus::STOPPED);
}
void AlsaSound::Clear(bool muted)
{
m_muted = muted;
if (m_muted)
{
std::lock_guard<std::mutex> lock(cv_m);
snd_pcm_drop(handle);
}
else
{
std::unique_lock<std::mutex> lock(cv_m);
snd_pcm_prepare(handle);
lock.unlock();
cv.notify_one();
}
}
bool AlsaSound::AlsaInit()
{
unsigned int sample_rate = m_mixer->GetSampleRate();