Get rid of lock(this)

- Use readonly object as lock

Info from stackoverflow:

If I want to be sure that it will be locked for all threads inside my
application:
The lock object has to be static, if it locks access to static state.
Otherwise it has to be instance, because there's no need to lock state of
one class instance, and prevent other threads to work with another class
instance at the same time.

everyone says that the object has to be "readonly" I didn't found the
reason
Well, it doesn't have to be. This is just a best practice, which helps you
to avoid errors.

Signed-off-by: Syrone Wong <wong.syrone@gmail.com>

shadowsocks-csharp/Controller/Service/PortForwarder.cs

@@ -39,6 +39,9 @@ namespace Shadowsocks.Controller
             // connection receive buffer
             private byte[] connetionRecvBuffer = new byte[RecvSize];
 
+            // instance-based lock
+            private readonly object _Lock = new object();
+
             public void Start(byte[] firstPacket, int length, Socket socket, int targetPort)
             {
                 this._firstPacket = firstPacket;
@@ -220,7 +223,7 @@ namespace Shadowsocks.Controller
 
             public void Close()
             {
-                lock (this)
+                lock (_Lock)
                 {
                     if (_closed)
                     {

shadowsocks-csharp/Controller/Service/TCPRelay.cs

@@ -160,8 +160,10 @@ namespace Shadowsocks.Controller
         private bool    _remoteShutdown = false;
         private bool    _closed = false;
 
-        private object  _encryptionLock = new object();
-        private object  _decryptionLock = new object();
+        // instance-based lock without static
+        private readonly object  _encryptionLock = new object();
+        private readonly object  _decryptionLock = new object();
+        private readonly object  _closeConnLock = new object();
 
         private DateTime _startConnectTime;
         private DateTime _startReceivingTime;
@@ -207,7 +209,7 @@ namespace Shadowsocks.Controller
 
         public void Close()
         {
-            lock (this)
+            lock (_closeConnLock)
             {
                 if (_closed) return;
                 _closed = true;

shadowsocks-csharp/Encryption/MbedTLSEncryptor.cs

@@ -15,6 +15,9 @@ namespace Shadowsocks.Encryption
         private IntPtr _encryptCtx = IntPtr.Zero;
         private IntPtr _decryptCtx = IntPtr.Zero;
 
+        // instance based lock
+        private readonly object _Lock = new object();
+
         public MbedTLSEncryptor(string method, string password, bool onetimeauth, bool isudp)
             : base(method, password, onetimeauth, isudp)
         {
@@ -120,7 +123,7 @@ namespace Shadowsocks.Encryption
 
         protected virtual void Dispose(bool disposing)
         {
-            lock (this)
+            lock (_Lock)
             {
                 if (_disposed)
                 {

shadowsocks-csharp/View/LogForm.cs

@@ -34,6 +34,9 @@ namespace Shadowsocks.View
         const int BACK_OFFSET = 65536;
         ShadowsocksController controller;
 
+        // global traffic update lock, make it static
+        private static readonly object _lock = new object();
+
         #region chart
         long lastMaxSpeed;
         ShadowsocksController.QueueLast<TrafficInfo> traffic = new ShadowsocksController.QueueLast<TrafficInfo>();
@@ -71,7 +74,7 @@ namespace Shadowsocks.View
             long maxSpeed = 0;
             long lastInbound, lastOutbound;
 
-            lock (this)
+            lock (_lock)
             {
                 if (traffic.Count == 0)
                     return;
@@ -120,7 +123,7 @@ namespace Shadowsocks.View
 
         private void controller_TrafficChanged(object sender, EventArgs e)
         {
-            lock (this)
+            lock (_lock)
             {
                 traffic = new ShadowsocksController.QueueLast<TrafficInfo>();
                 foreach (var trafficPerSecond in controller.traffic)