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

1 files changed, 13 insertions, 9 deletions

diff --git a/framework/java/android/bluetooth/BluetoothPbap.java b/framework/java/android/bluetooth/BluetoothPbap.java
index 78b7c7b7a7..19f5198ca7 100644
--- a/framework/java/android/bluetooth/BluetoothPbap.java
+++ b/framework/java/android/bluetooth/BluetoothPbap.java
@@ -68,7 +68,7 @@ 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;
@@ -214,9 +214,10 @@ public class BluetoothPbap {
      */
     public int getState() {
         if (VDBG) log("getState()");
-        if (mService != null) {
+        final IBluetoothPbap service = mService;
+        if (service != null) {
             try {
-                return mService.getState();
+                return service.getState();
             } catch (RemoteException e) {
                 Log.e(TAG, e.toString());
             }
@@ -235,9 +236,10 @@ public class BluetoothPbap {
      */
     public BluetoothDevice getClient() {
         if (VDBG) log("getClient()");
-        if (mService != null) {
+        final IBluetoothPbap service = mService;
+        if (service != null) {
             try {
-                return mService.getClient();
+                return service.getClient();
             } catch (RemoteException e) {
                 Log.e(TAG, e.toString());
             }
@@ -255,9 +257,10 @@ 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);
+                return service.isConnected(device);
             } catch (RemoteException e) {
                 Log.e(TAG, e.toString());
             }
@@ -275,9 +278,10 @@ 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());