Fix deadlock (#144)

pkg/emulator/libretro/nanoarch/naemulator.go

@@ -3,6 +3,7 @@ package nanoarch
 import (
 	"image"
 	"log"
+	"sync"
 	"time"
 
 	"github.com/giongto35/cloud-game/pkg/config"
@@ -59,6 +60,9 @@ type naEmulator struct {
 
 	keys []bool
 	done chan struct{}
+
+	// lock to lock uninteruptable operation
+	lock *sync.Mutex
 }
 
 var NAEmulator *naEmulator
@@ -78,6 +82,7 @@ func NewNAEmulator(etype string, roomID string, inputChannel <-chan int) (*naEmu
 		keys:         make([]bool, joypadNumKeys),
 		roomID:       roomID,
 		done:         make(chan struct{}, 1),
+		lock:         &sync.Mutex{},
 	}, imageChannel, audioChannel
 }
 

pkg/emulator/libretro/nanoarch/savestates.go

@@ -18,20 +18,16 @@ import "C"
 
 import (
 	"io/ioutil"
-	"sync"
 )
 
-var saveLock int32
-var m sync.Mutex
-
 func (na *naEmulator) GetLock() {
-	//atomic.CompareAndSwapInt32(&saveLock, 0, 1)
-	m.Lock()
+	//atomic.CompareAndSwapInt32(&na.saveLock, 0, 1)
+	na.lock.Lock()
 }
 
 func (na *naEmulator) ReleaseLock() {
-	//atomic.CompareAndSwapInt32(&saveLock, 1, 0)
-	m.Unlock()
+	//atomic.CompareAndSwapInt32(&na.saveLock, 1, 0)
+	na.lock.Unlock()
 }
 
 // Save the current state to the filesystem. name is the name of the

pkg/worker/room/room.go

@@ -199,6 +199,7 @@ func (r *Room) startWebRTCSession(peerconnection *webrtc.WebRTC, playerIndex int
 		}
 	}()
 
+	// bug: when inputchannel here = nil , skip and finish
 	for input := range peerconnection.InputChannel {
 		// NOTE: when room is no longer running. InputChannel needs to have extra event to go inside the loop
 		if peerconnection.Done || !peerconnection.IsConnected() || !r.IsRunning {
@@ -258,9 +259,16 @@ func (r *Room) Close() {
 	// Save game before quit. Only save for game which was previous saved to avoid flooding database
 	if r.isRoomExisted() {
 		log.Println("Saved Game before closing room")
-		r.SaveGame()
+		// use goroutine here because SaveGame attempt to acquire a emulator lock.
+		// the lock is holding before coming to close, so it will cause deadlock if SaveGame is synchronous
+		go func() {
+			// Save before close, so save can have correct state (Not sure) may again cause deadlock
+			r.SaveGame()
+			r.director.Close()
+		}()
+	} else {
+		r.director.Close()
 	}
-	r.director.Close()
 	log.Println("Closing input of room ", r.ID)
 	close(r.inputChannel)
 	close(r.Done)