DO NOT MERGE Fix bug in getCurrentLocation cancellation

Cancellation was not being propagated to the system server due to a
misunderstanding on how CancellationSignal functions. There is no
noticable impact for the user, as cancellation did properly prevent any
further locations, however this would have resulted in extra
power draw since the system server would not have canceled the
associated provider location request. This would have left
getCurrentLocation() as equivalent to requestSingleUpdate() where it was
supposed to be an all-around improvement that could save power.

Bug: 168666216
Test: manual + presubmits
Change-Id: I5c77db4cc56cce1b984587f65d2bcfb488436bb8

location/java/android/location/ILocationManager.aidl

@@ -45,9 +45,9 @@ import com.android.internal.location.ProviderProperties;
 interface ILocationManager
 {
     Location getLastLocation(in LocationRequest request, String packageName, String featureId);
-    boolean getCurrentLocation(in LocationRequest request,
-            in ICancellationSignal cancellationSignal, in ILocationListener listener,
-            String packageName, String featureId, String listenerId);
+    @nullable ICancellationSignal getCurrentLocation(in LocationRequest request,
+            in ILocationListener listener, String packageName, String featureId,
+            String listenerId);
 
     void requestLocationUpdates(in LocationRequest request, in ILocationListener listener,
             in PendingIntent intent, String packageName, String featureId, String listenerId);

location/java/android/location/LocationManager.java

@@ -726,16 +726,15 @@ public class LocationManager {
             cancellationSignal.throwIfCanceled();
         }
 
-        ICancellationSignal remoteCancellationSignal = CancellationSignal.createTransport();
-
         try {
-            if (mService.getCurrentLocation(currentLocationRequest, remoteCancellationSignal,
-                    transport, mContext.getPackageName(), mContext.getAttributionTag(),
-                    transport.getListenerId())) {
+            ICancellationSignal cancelRemote = mService.getCurrentLocation(
+                    currentLocationRequest, transport, mContext.getPackageName(),
+                    mContext.getAttributionTag(), transport.getListenerId());
+            if (cancelRemote != null) {
                 transport.register(mContext.getSystemService(AlarmManager.class),
-                        remoteCancellationSignal);
+                        cancellationSignal);
                 if (cancellationSignal != null) {
-                    cancellationSignal.setOnCancelListener(transport::cancel);
+                    cancellationSignal.setRemote(cancelRemote);
                 }
             } else {
                 transport.fail();
@@ -2540,7 +2539,7 @@ public class LocationManager {
     }
 
     private static class GetCurrentLocationTransport extends ILocationListener.Stub implements
-            AlarmManager.OnAlarmListener {
+            AlarmManager.OnAlarmListener, CancellationSignal.OnCancelListener {
 
         @GuardedBy("this")
         @Nullable
@@ -2572,7 +2571,7 @@ public class LocationManager {
         }
 
         public synchronized void register(AlarmManager alarmManager,
-                ICancellationSignal remoteCancellationSignal) {
+                CancellationSignal cancellationSignal) {
             if (mConsumer == null) {
                 return;
             }
@@ -2585,16 +2584,18 @@ public class LocationManager {
                     this,
                     null);
 
-            mRemoteCancellationSignal = remoteCancellationSignal;
+            if (cancellationSignal != null) {
+                cancellationSignal.setOnCancelListener(this);
+            }
         }
 
-        public void cancel() {
+        @Override
+        public void onCancel() {
             remove();
         }
 
         private Consumer<Location> remove() {
             Consumer<Location> consumer;
-            ICancellationSignal cancellationSignal;
             synchronized (this) {
                 mExecutor = null;
                 consumer = mConsumer;
@@ -2604,18 +2605,6 @@ public class LocationManager {
                     mAlarmManager.cancel(this);
                     mAlarmManager = null;
                 }
-
-                // ensure only one cancel event will go through
-                cancellationSignal = mRemoteCancellationSignal;
-                mRemoteCancellationSignal = null;
-            }
-
-            if (cancellationSignal != null) {
-                try {
-                    cancellationSignal.cancel();
-                } catch (RemoteException e) {
-                    // ignore
-                }
             }
 
             return consumer;
@@ -2637,11 +2626,6 @@ public class LocationManager {
 
         @Override
         public void onLocationChanged(Location location) {
-            synchronized (this) {
-                // save ourselves a pointless x-process call to cancel the location request
-                mRemoteCancellationSignal = null;
-            }
-
             deliverResult(location);
         }
 

services/core/java/com/android/server/location/LocationManagerService.java

@@ -2064,10 +2064,12 @@ public class LocationManagerService extends ILocationManager.Stub {
         }
     }
 
+    @Nullable
     @Override
-    public boolean getCurrentLocation(LocationRequest locationRequest,
-            ICancellationSignal remoteCancellationSignal, ILocationListener listener,
-            String packageName, String featureId, String listenerId) {
+    public ICancellationSignal getCurrentLocation(LocationRequest locationRequest,
+            ILocationListener listener, String packageName, String featureId, String listenerId) {
+        ICancellationSignal remoteCancellationSignal = CancellationSignal.createTransport();
+
         // side effect of validating locationRequest and packageName
         Location lastLocation = getLastLocation(locationRequest, packageName, featureId);
         if (lastLocation != null) {
@@ -2077,17 +2079,17 @@ public class LocationManagerService extends ILocationManager.Stub {
             if (locationAgeMs < MAX_CURRENT_LOCATION_AGE_MS) {
                 try {
                     listener.onLocationChanged(lastLocation);
-                    return true;
+                    return remoteCancellationSignal;
                 } catch (RemoteException e) {
                     Log.w(TAG, e);
-                    return false;
+                    return null;
                 }
             }
 
             if (!mAppForegroundHelper.isAppForeground(Binder.getCallingUid())) {
                 if (locationAgeMs < mSettingsHelper.getBackgroundThrottleIntervalMs()) {
                     // not allowed to request new locations, so we can't return anything
-                    return false;
+                    return null;
                 }
             }
         }
@@ -2095,11 +2097,8 @@ public class LocationManagerService extends ILocationManager.Stub {
         requestLocationUpdates(locationRequest, listener, null, packageName, featureId, listenerId);
         CancellationSignal cancellationSignal = CancellationSignal.fromTransport(
                 remoteCancellationSignal);
-        if (cancellationSignal != null) {
-            cancellationSignal.setOnCancelListener(
-                    () -> removeUpdates(listener, null));
-        }
-        return true;
+        cancellationSignal.setOnCancelListener(() -> removeUpdates(listener, null));
+        return remoteCancellationSignal;
     }
 
     @Override