make 64bit atomics also align on 32bit (#2386)

do this by simply putting them at the front of each struct
see https://pkg.go.dev/sync/atomic#pkg-note-BUG

fixes #2383

Co-authored-by: akarl10 <mike@mwys.mine.bz>

pkg/rtc/participant.go

@@ -137,6 +137,10 @@ type ParticipantParams struct {
 }
 
 type ParticipantImpl struct {
+	// utils.TimedVersion is a atomic. To be correctly aligned also on 32bit archs
+	// 64it atomics need to be at the front of a struct
+	timedVersion utils.TimedVersion
+
 	params ParticipantParams
 
 	isClosed    atomic.Bool
@@ -200,7 +204,6 @@ type ParticipantImpl struct {
 
 	dirty        atomic.Bool
 	version      atomic.Uint32
-	timedVersion utils.TimedVersion
 
 	// callbacks & handlers
 	onTrackPublished     func(types.LocalParticipant, types.MediaTrack)

pkg/rtc/room.go

@@ -80,6 +80,15 @@ type disconnectSignalOnResumeNoMessages struct {
 }
 
 type Room struct {
+	// atomics always need to be 64bit/8byte aligned
+	// on 32bit arch only the beginning of the struct
+	// starts at such a boundary.
+	// time the first participant joined the room
+	joinedAt atomic.Int64
+	// time that the last participant left the room
+	leftAt atomic.Int64
+	holds    atomic.Int32
+
 	lock sync.RWMutex
 
 	protoRoom  *livekit.Room
@@ -109,11 +118,6 @@ type Room struct {
 	batchedUpdates   map[livekit.ParticipantIdentity]*participantUpdate
 	batchedUpdatesMu sync.Mutex
 
-	// time the first participant joined the room
-	joinedAt atomic.Int64
-	holds    atomic.Int32
-	// time that the last participant left the room
-	leftAt atomic.Int64
 	closed chan struct{}
 
 	trailer []byte

pkg/rtc/uptrackmanager.go

@@ -37,6 +37,10 @@ type UpTrackManagerParams struct {
 
 // UpTrackManager manages all uptracks from a participant
 type UpTrackManager struct {
+	// utils.TimedVersion is a atomic. To be correctly aligned also on 32bit archs
+	// 64it atomics need to be at the front of a struct
+	subscriptionPermissionVersion utils.TimedVersion
+
 	params UpTrackManagerParams
 
 	closed bool
@@ -44,7 +48,6 @@ type UpTrackManager struct {
 	// publishedTracks that participant is publishing
 	publishedTracks               map[livekit.TrackID]types.MediaTrack
 	subscriptionPermission        *livekit.SubscriptionPermission
-	subscriptionPermissionVersion utils.TimedVersion
 	// subscriber permission for published tracks
 	subscriberPermissions map[livekit.ParticipantIdentity]*livekit.TrackPermission // subscriberIdentity => *livekit.TrackPermission