Bluetooth: Thread-safe binder invocation

* Binder object may become null between null check and actual invocation
  if using a instance private variable assignable by service connection
  callbacks
* The solution to this problem without locking is to assign existing
  binder variable to a local final variable before the null check
* Any further invocation to a disconnected binder object will result in
  RemoteException that is caught by the try-catch block
* Read and write to volatile variable is always atomic and hence thread-safe
* Removed unnecessary synchronization in BluetoothAdapter constructor
* Private mConnection objects should be final
* Simplfied several return statements where booleans can be returned
  directly
* Removed unnecessary catches for NPE since there won't be any

Bug: 64724692
Test: make, pair and use devices, no functional change
Change-Id: Ifc9d6337c0d451a01484b61243230725d5314f8e
(cherry picked from commit 1f686f645294d624f8b61e4761fd14787a496c75)

1 files changed, 23 insertions, 13 deletions

diff --git a/framework/java/android/bluetooth/BluetoothPbap.java b/framework/java/android/bluetooth/BluetoothPbap.java
index dc01fc7a94..f16160e475 100644
--- a/framework/java/android/bluetooth/BluetoothPbap.java
+++ b/framework/java/android/bluetooth/BluetoothPbap.java
@@ -20,8 +20,8 @@ import android.content.ComponentName;
 import android.content.Context;
 import android.content.Intent;
 import android.content.ServiceConnection;
-import android.os.RemoteException;
 import android.os.IBinder;
+import android.os.RemoteException;
 import android.util.Log;
 
 /**
@@ -67,7 +67,7 @@ public class BluetoothPbap {
     public static final String PBAP_STATE_CHANGED_ACTION =
         "android.bluetooth.pbap.intent.action.PBAP_STATE_CHANGED";
 
-    private IBluetoothPbap mService;
+    private volatile IBluetoothPbap mService;
     private final Context mContext;
     private ServiceListener mServiceListener;
     private BluetoothAdapter mAdapter;
@@ -212,10 +212,13 @@ public class BluetoothPbap {
      */
     public int getState() {
         if (VDBG) log("getState()");
-        if (mService != null) {
+        final IBluetoothPbap service = mService;
+        if (service != null) {
             try {
-                return mService.getState();
-            } catch (RemoteException e) {Log.e(TAG, e.toString());}
+                return service.getState();
+            } catch (RemoteException e) {
+                Log.e(TAG, e.toString());
+            }
         } else {
             Log.w(TAG, "Proxy not attached to service");
             if (DBG) log(Log.getStackTraceString(new Throwable()));
@@ -231,10 +234,13 @@ public class BluetoothPbap {
      */
     public BluetoothDevice getClient() {
         if (VDBG) log("getClient()");
-        if (mService != null) {
+        final IBluetoothPbap service = mService;
+        if (service != null) {
             try {
-                return mService.getClient();
-            } catch (RemoteException e) {Log.e(TAG, e.toString());}
+                return service.getClient();
+            } catch (RemoteException e) {
+                Log.e(TAG, e.toString());
+            }
         } else {
             Log.w(TAG, "Proxy not attached to service");
             if (DBG) log(Log.getStackTraceString(new Throwable()));
@@ -249,10 +255,13 @@ public class BluetoothPbap {
      */
     public boolean isConnected(BluetoothDevice device) {
         if (VDBG) log("isConnected(" + device + ")");
-        if (mService != null) {
+        final IBluetoothPbap service = mService;
+        if (service != null) {
             try {
-                return mService.isConnected(device);
-            } catch (RemoteException e) {Log.e(TAG, e.toString());}
+                return service.isConnected(device);
+            } catch (RemoteException e) {
+                Log.e(TAG, e.toString());
+            }
         } else {
             Log.w(TAG, "Proxy not attached to service");
             if (DBG) log(Log.getStackTraceString(new Throwable()));
@@ -267,9 +276,10 @@ public class BluetoothPbap {
      */
     public boolean disconnect() {
         if (DBG) log("disconnect()");
-        if (mService != null) {
+        final IBluetoothPbap service = mService;
+        if (service != null) {
             try {
-                mService.disconnect();
+                service.disconnect();
                 return true;
             } catch (RemoteException e) {Log.e(TAG, e.toString());}
         } else {