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Code Issues Releases Activity

Workaround for a potential deadlock in MusicHandler

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This commit is contained in:
Ivan Savenko 2022-12-26 21:05:01 +02:00
parent d6674e73cd
commit 588b635d1c
1 changed files with 26 additions and 4 deletions
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30
client/CMusicHandler.cpp
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@ -409,6 +409,8 @@ void CMusicHandler::release()
void CMusicHandler::playMusic(const std::string & musicURI, bool loop, bool fromStart)
{
boost::mutex::scoped_lock guard(mutex);
if (current && current->isPlaying() && current->isTrack(musicURI))
return;
@ -422,6 +424,8 @@ void CMusicHandler::playMusicFromSet(const std::string & musicSet, const std::st
void CMusicHandler::playMusicFromSet(const std::string & whichSet, bool loop, bool fromStart)
{
boost::mutex::scoped_lock guard(mutex);
auto selectedSet = musicsSet.find(whichSet);
if (selectedSet == musicsSet.end())
{
@ -441,8 +445,6 @@ void CMusicHandler::queueNext(std::unique_ptr<MusicEntry> queued)
if (!initialized)
return;
boost::mutex::scoped_lock guard(mutex);
next = std::move(queued);
if (current.get() == nullptr || !current->stop(1000))
@ -487,13 +489,32 @@ void CMusicHandler::setVolume(ui32 percent)
void CMusicHandler::musicFinishedCallback()
{
boost::mutex::scoped_lock guard(mutex);
// boost::mutex::scoped_lock guard(mutex);
// FIXME: WORKAROUND FOR A POTENTIAL DEADLOCK
// It is possible for:
// 1) SDL thread to call this method on end of playback
// 2) VCMI code to call queueNext() method to queue new file
// this leads to:
// 1) SDL thread waiting to aquire music lock in this method (while keeping internal SDL mutex locked)
// 2) VCMI thread waiting to aquire internal SDL mutex (while keeping music mutex locked)
// Because of that (and lack of clear way to fix that)
// We will try to acquire lock here and if failed - do nothing
// This may break music playback till next song is enqued but won't deadlock the game
if (!mutex.try_lock())
{
logGlobal->error("Failed to aquire mutex! Unable to restart music!");
return;
}
if (current.get() != nullptr)
{
// if music is looped, play it again
if (current->play())
{
mutex.unlock();
return;
}
else
current.reset();
}
@ -503,6 +524,7 @@ void CMusicHandler::musicFinishedCallback()
current.reset(next.release());
current->play();
}
mutex.unlock();
}
MusicEntry::MusicEntry(CMusicHandler *owner, std::string setName, std::string musicURI, bool looped, bool fromStart):
@ -597,7 +619,7 @@ bool MusicEntry::play()
bool MusicEntry::stop(int fade_ms)
{
if (Mix_PlayingMusic())
if (playing)
{
playing = false;
loop = 0;