diff --git a/services/core/java/com/android/server/am/BatteryStatsService.java b/services/core/java/com/android/server/am/BatteryStatsService.java
index 773e3137c2476..c363a7c3336a6 100644
--- a/services/core/java/com/android/server/am/BatteryStatsService.java
+++ b/services/core/java/com/android/server/am/BatteryStatsService.java
@@ -128,13 +128,18 @@ public final class BatteryStatsService extends IBatteryStats.Stub
                     .replaceWith("?");
     private static final int MAX_LOW_POWER_STATS_SIZE = 4096;
     private static final int POWER_STATS_QUERY_TIMEOUT_MILLIS = 2000;
+    private static final String EMPTY = "Empty";
 
     private final HandlerThread mHandlerThread;
     private final Handler mHandler;
     private final Object mLock = new Object();
 
+    private final Object mPowerStatsLock = new Object();
+    @GuardedBy("mPowerStatsLock")
     private PowerStatsInternal mPowerStatsInternal = null;
+    @GuardedBy("mPowerStatsLock")
     private Map<Integer, String> mEntityNames = new HashMap();
+    @GuardedBy("mPowerStatsLock")
     private Map<Integer, Map<Integer, String>> mStateNames = new HashMap();
 
     @GuardedBy("mStats")
@@ -172,13 +177,6 @@ public final class BatteryStatsService extends IBatteryStats.Stub
             };
 
     private void populatePowerEntityMaps() {
-        if (mPowerStatsInternal == null) {
-            // PowerStatsInternal unavailable, don't bother populating maps.
-            mEntityNames = null;
-            mStateNames = null;
-            return;
-        }
-
         PowerEntity[] entities = mPowerStatsInternal.getPowerEntityInfo();
         if (entities == null) {
             return;
@@ -202,6 +200,12 @@ public final class BatteryStatsService extends IBatteryStats.Stub
      */
     @Override
     public void fillLowPowerStats(RpmStats rpmStats) {
+        synchronized (mPowerStatsLock) {
+            if (mPowerStatsInternal == null || mEntityNames.isEmpty() || mStateNames.isEmpty()) {
+                return;
+            }
+        }
+
         final StateResidencyResult[] results;
         try {
             results = mPowerStatsInternal.getStateResidencyAsync(new int[0])
@@ -237,16 +241,22 @@ public final class BatteryStatsService extends IBatteryStats.Stub
 
     @Override
     public String getSubsystemLowPowerStats() {
+        synchronized (mPowerStatsLock) {
+            if (mPowerStatsInternal == null || mEntityNames.isEmpty() || mStateNames.isEmpty()) {
+                return EMPTY;
+            }
+        }
+
         final StateResidencyResult[] results;
         try {
             results = mPowerStatsInternal.getStateResidencyAsync(new int[0])
                     .get(POWER_STATS_QUERY_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS);
         } catch (Exception e) {
             Slog.e(TAG, "Failed to getStateResidencyAsync", e);
-            return "Empty";
+            return EMPTY;
         }
 
-        if (results.length == 0) return "Empty";
+        if (results.length == 0) return EMPTY;
 
         int charsLeft = MAX_LOW_POWER_STATS_SIZE;
         StringBuilder builder = new StringBuilder("SubsystemPowerState");
@@ -322,9 +332,14 @@ public final class BatteryStatsService extends IBatteryStats.Stub
         } catch (RemoteException e) {
             Slog.e(TAG, "Could not register INetworkManagement event observer " + e);
         }
-        mPowerStatsInternal = LocalServices.getService(PowerStatsInternal.class);
-        if (mPowerStatsInternal != null) {
-            populatePowerEntityMaps();
+
+        synchronized (mPowerStatsLock) {
+            mPowerStatsInternal = LocalServices.getService(PowerStatsInternal.class);
+            if (mPowerStatsInternal != null) {
+                populatePowerEntityMaps();
+            } else {
+                Slog.e(TAG, "Could not register PowerStatsInternal");
+            }
         }
 
         Watchdog.getInstance().addMonitor(this);