diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index 4037c042f2fdc..670809f1d947f 100644
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -17002,6 +17002,7 @@ public class ActivityManagerService extends IActivityManager.Stub
 
         @Override
         public void addPendingTopUid(int uid, int pid) {
+            final boolean isNewPending = mPendingStartActivityUids.add(uid, pid);
             // If the next top activity is in cached and frozen mode, WM should raise its priority
             // to unfreeze it. This is done by calling AMS.updateOomAdj that will lower its oom adj.
             // However, WM cannot hold the AMS clock here so the updateOomAdj operation is performed
@@ -17009,11 +17010,9 @@ public class ActivityManagerService extends IActivityManager.Stub
             // next top activity on time. This race will fail the following binder transactions WM
             // sends to the activity. After this race issue between WM/ATMS and AMS is solved, this
             // workaround can be removed. (b/213288355)
-            if (!isPendingTopUid(uid)) {
+            if (isNewPending && mOomAdjuster != null) { // It can be null in unit test.
                 mOomAdjuster.mCachedAppOptimizer.unfreezeProcess(pid);
             }
-
-            mPendingStartActivityUids.add(uid, pid);
         }
 
         @Override
diff --git a/services/core/java/com/android/server/am/PendingStartActivityUids.java b/services/core/java/com/android/server/am/PendingStartActivityUids.java
index 802ea001e28c3..455c75b882189 100644
--- a/services/core/java/com/android/server/am/PendingStartActivityUids.java
+++ b/services/core/java/com/android/server/am/PendingStartActivityUids.java
@@ -46,10 +46,13 @@ final class PendingStartActivityUids {
         mContext = context;
     }
 
-    synchronized void add(int uid, int pid) {
+    /** Returns {@code true} if the uid is put to the pending array. Otherwise it existed. */
+    synchronized boolean add(int uid, int pid) {
         if (mPendingUids.get(uid) == null) {
             mPendingUids.put(uid, new Pair<>(pid, SystemClock.elapsedRealtime()));
+            return true;
         }
+        return false;
     }
 
     synchronized void delete(int uid) {