diff --git a/services/core/java/com/android/server/am/KeyguardController.java b/services/core/java/com/android/server/am/KeyguardController.java
index 2bd119ec177da..dd16e228cbe3e 100644
--- a/services/core/java/com/android/server/am/KeyguardController.java
+++ b/services/core/java/com/android/server/am/KeyguardController.java
@@ -204,12 +204,11 @@ class KeyguardController {
         mOccluded = false;
         mDismissingKeyguardActivity = null;
         final ArrayList<ActivityStack> stacks = mStackSupervisor.getStacksOnDefaultDisplay();
-        final int topStackNdx = stacks.size() - 1;
-        for (int stackNdx = topStackNdx; stackNdx >= 0; --stackNdx) {
+        for (int stackNdx = stacks.size() - 1; stackNdx >= 0; --stackNdx) {
             final ActivityStack stack = stacks.get(stackNdx);
 
-            // Only the very top activity may control occluded state
-            if (stackNdx == topStackNdx) {
+            // Only the focused stack top activity may control occluded state
+            if (mStackSupervisor.isFocusedStack(stack)) {
 
                 // A dismissing activity occludes Keyguard in the insecure case for legacy reasons.
                 final ActivityRecord topDismissing = stack.getTopDismissingKeyguardActivity();
diff --git a/services/core/java/com/android/server/wm/AppWindowToken.java b/services/core/java/com/android/server/wm/AppWindowToken.java
index 763464422e563..936739bf143ea 100644
--- a/services/core/java/com/android/server/wm/AppWindowToken.java
+++ b/services/core/java/com/android/server/wm/AppWindowToken.java
@@ -95,6 +95,9 @@ class AppWindowToken extends WindowToken implements WindowManagerService.AppFree
     // change.
     private boolean mReparenting;
 
+    // True if we are current in the process of removing this app token from the display
+    private boolean mRemovingFromDisplay = false;
+
     // The input dispatching timeout for this application token in nanoseconds.
     long mInputDispatchingTimeoutNanos;
 
@@ -464,6 +467,12 @@ class AppWindowToken extends WindowToken implements WindowManagerService.AppFree
         return !hidden;
     }
 
+    @Override
+    void removeImmediately() {
+        onRemovedFromDisplay();
+        super.removeImmediately();
+    }
+
     @Override
     void removeIfPossible() {
         mIsExiting = false;
@@ -480,6 +489,11 @@ class AppWindowToken extends WindowToken implements WindowManagerService.AppFree
     }
 
     void onRemovedFromDisplay() {
+        if (mRemovingFromDisplay) {
+            return;
+        }
+        mRemovingFromDisplay = true;
+
         if (DEBUG_APP_TRANSITIONS) Slog.v(TAG_WM, "Removing app token: " + this);
 
         boolean delayed = setVisibility(null, false, TRANSIT_UNSET, true, mVoiceInteraction);
@@ -512,12 +526,14 @@ class AppWindowToken extends WindowToken implements WindowManagerService.AppFree
             mService.mNoAnimationNotifyOnTransitionFinished.add(token);
         }
 
-        final TaskStack stack = getTask().mStack;
+        final TaskStack stack = getStack();
         if (delayed && !isEmpty()) {
             // set the token aside because it has an active animation to be finished
             if (DEBUG_ADD_REMOVE || DEBUG_TOKEN_MOVEMENT) Slog.v(TAG_WM,
                     "removeAppToken make exiting: " + this);
-            stack.mExitingAppTokens.add(this);
+            if (stack != null) {
+                stack.mExitingAppTokens.add(this);
+            }
             mIsExiting = true;
         } else {
             // Make sure there is no animation running on this token, so any windows associated
@@ -540,6 +556,8 @@ class AppWindowToken extends WindowToken implements WindowManagerService.AppFree
         if (!delayed) {
             updateReportedVisibilityLocked();
         }
+
+        mRemovingFromDisplay = false;
     }
 
     void clearAnimatingFlags() {
@@ -1558,6 +1576,9 @@ class AppWindowToken extends WindowToken implements WindowManagerService.AppFree
         if (getController() != null) {
             pw.print(prefix); pw.print("controller="); pw.println(getController());
         }
+        if (mRemovingFromDisplay) {
+            pw.println(prefix + "mRemovingFromDisplay=" + mRemovingFromDisplay);
+        }
     }
 
     @Override
diff --git a/services/core/java/com/android/server/wm/WindowManagerService.java b/services/core/java/com/android/server/wm/WindowManagerService.java
index 252b4d4e0473a..5fbc43f69c8d5 100644
--- a/services/core/java/com/android/server/wm/WindowManagerService.java
+++ b/services/core/java/com/android/server/wm/WindowManagerService.java
@@ -5606,22 +5606,19 @@ public class WindowManagerService extends IWindowManager.Stub
         WindowState win = mWindowMap.get(client);
         if (localLOGV) Slog.v(TAG_WM, "Looking up client " + client + ": " + win);
         if (win == null) {
-            RuntimeException ex = new IllegalArgumentException(
-                    "Requested window " + client + " does not exist");
             if (throwOnError) {
-                throw ex;
+                throw new IllegalArgumentException(
+                        "Requested window " + client + " does not exist");
             }
-            Slog.w(TAG_WM, "Failed looking up window", ex);
+            Slog.w(TAG_WM, "Failed looking up window callers=" + Debug.getCallers(3));
             return null;
         }
         if (session != null && win.mSession != session) {
-            RuntimeException ex = new IllegalArgumentException(
-                    "Requested window " + client + " is in session " +
-                    win.mSession + ", not " + session);
             if (throwOnError) {
-                throw ex;
+                throw new IllegalArgumentException("Requested window " + client + " is in session "
+                        + win.mSession + ", not " + session);
             }
-            Slog.w(TAG_WM, "Failed looking up window", ex);
+            Slog.w(TAG_WM, "Failed looking up window callers=" + Debug.getCallers(3));
             return null;
         }