[Scummvm-git-logs] scummvm master -> 2803adc0b82f0e260fd25281719529373c3096bb

[bluegr]

This automated email contains information about 2 new commits which have been
pushed to the 'scummvm' repo located at https://github.com/scummvm/scummvm .

Summary:
2ef6e24e56 SCI: avoid deadlocks by using only one mutex
2803adc0b8 SCI: update mutex comment


Commit: 2ef6e24e569cefd3e99198c5ed6f374fd0c8bb7a
    https://github.com/scummvm/scummvm/commit/2ef6e24e569cefd3e99198c5ed6f374fd0c8bb7a
Author: athrxx (athrxx at scummvm.org)
Date: 2022-06-03T23:42:02+03:00

Commit Message:
SCI: avoid deadlocks by using only one mutex

Make use of the mixer's mutex instead of creating a new one. Otherwise there can still be lock-ups when the main thread and the mixer thread lock each other up in different mutexes (causing a deadlock/freeze). I just noticed this with KQ5 FM-Towns.

We had the same issue in AGOS, it was fixed by allowing to access the mixer's mutex. We can use the same thing here...

Changed paths:
    engines/sci/sound/music.cpp
    engines/sci/sound/music.h


diff --git a/engines/sci/sound/music.cpp b/engines/sci/sound/music.cpp
index a5d0720451d..d62afe79473 100644
--- a/engines/sci/sound/music.cpp
+++ b/engines/sci/sound/music.cpp
@@ -39,7 +39,7 @@
 namespace Sci {
 
 SciMusic::SciMusic(SciVersion soundVersion, bool useDigitalSFX)
-	: _soundVersion(soundVersion), _soundOn(true), _masterVolume(15), _globalReverb(0), _useDigitalSFX(useDigitalSFX), _needsResume(soundVersion > SCI_VERSION_0_LATE), _globalPause(0) {
+	: _mutex(g_system->getMixer()->mutex()), _soundVersion(soundVersion), _soundOn(true), _masterVolume(15), _globalReverb(0), _useDigitalSFX(useDigitalSFX), _needsResume(soundVersion > SCI_VERSION_0_LATE), _globalPause(0) {
 
 	// Reserve some space in the playlist, to avoid expensive insertion
 	// operations
diff --git a/engines/sci/sound/music.h b/engines/sci/sound/music.h
index 3fd988d69da..38f0f005984 100644
--- a/engines/sci/sound/music.h
+++ b/engines/sci/sound/music.h
@@ -261,7 +261,7 @@ public:
 	// MIDI parser and to the MIDI driver/player. Note that guarded code must NOT
 	// include references to the mixer, otherwise there will probably be situations
 	// where a deadlock can occur
-	Common::Mutex _mutex;
+	Common::Mutex &_mutex;
 
 protected:
 	void sortPlayList();


Commit: 2803adc0b82f0e260fd25281719529373c3096bb
    https://github.com/scummvm/scummvm/commit/2803adc0b82f0e260fd25281719529373c3096bb
Author: athrxx (athrxx at scummvm.org)
Date: 2022-06-03T23:42:02+03:00

Commit Message:
SCI: update mutex comment

(after turning _mutex into a reference to the mixers's mutex)

Changed paths:
    engines/sci/sound/music.h


diff --git a/engines/sci/sound/music.h b/engines/sci/sound/music.h
index 38f0f005984..68e11eddff9 100644
--- a/engines/sci/sound/music.h
+++ b/engines/sci/sound/music.h
@@ -258,9 +258,9 @@ public:
 	void saveLoadWithSerializer(Common::Serializer &ser) override;
 
 	// Mutex for music code. Used to guard access to the song playlist, to the
-	// MIDI parser and to the MIDI driver/player. Note that guarded code must NOT
-	// include references to the mixer, otherwise there will probably be situations
-	// where a deadlock can occur
+	// MIDI parser and to the MIDI driver/player. We use a reference to
+	// the mixer's internal mutex to avoid deadlocks which sometimes occur when
+	// different threads lock each other up in different mutexes.
 	Common::Mutex &_mutex;
 
 protected: