diff --git a/core/java/android/content/pm/ActivityInfo.java b/core/java/android/content/pm/ActivityInfo.java
index 0673b3ad5b0a6..a3d595ef65756 100644
--- a/core/java/android/content/pm/ActivityInfo.java
+++ b/core/java/android/content/pm/ActivityInfo.java
@@ -106,6 +106,24 @@ public class ActivityInfo extends ComponentInfo implements Parcelable {
     public @interface LaunchMode {
     }
 
+    /** @hide */
+    public static String launchModeToString(@LaunchMode int launchMode) {
+        switch(launchMode) {
+            case LAUNCH_MULTIPLE:
+                return "LAUNCH_MULTIPLE";
+            case LAUNCH_SINGLE_TOP:
+                return "LAUNCH_SINGLE_TOP";
+            case LAUNCH_SINGLE_TASK:
+                return "LAUNCH_SINGLE_TASK";
+            case LAUNCH_SINGLE_INSTANCE:
+                return "LAUNCH_SINGLE_INSTANCE";
+            case LAUNCH_SINGLE_INSTANCE_PER_TASK:
+                return "LAUNCH_SINGLE_INSTANCE_PER_TASK";
+            default:
+                return "unknown=" + launchMode;
+        }
+    }
+
     /**
      * The launch mode style requested by the activity.  From the
      * {@link android.R.attr#launchMode} attribute.
@@ -1585,7 +1603,7 @@ public class ActivityInfo extends ComponentInfo implements Parcelable {
                     + " persistableMode=" + persistableModeToString());
         }
         if (launchMode != 0 || flags != 0 || privateFlags != 0 || theme != 0) {
-            pw.println(prefix + "launchMode=" + launchMode
+            pw.println(prefix + "launchMode=" + launchModeToString(launchMode)
                     + " flags=0x" + Integer.toHexString(flags)
                     + " privateFlags=0x" + Integer.toHexString(privateFlags)
                     + " theme=0x" + Integer.toHexString(theme));
diff --git a/services/core/java/com/android/server/wm/ActivityStarter.java b/services/core/java/com/android/server/wm/ActivityStarter.java
index f7367dfdf1220..a30c7445225b9 100644
--- a/services/core/java/com/android/server/wm/ActivityStarter.java
+++ b/services/core/java/com/android/server/wm/ActivityStarter.java
@@ -51,6 +51,7 @@ import static android.content.pm.ActivityInfo.LAUNCH_SINGLE_INSTANCE;
 import static android.content.pm.ActivityInfo.LAUNCH_SINGLE_INSTANCE_PER_TASK;
 import static android.content.pm.ActivityInfo.LAUNCH_SINGLE_TASK;
 import static android.content.pm.ActivityInfo.LAUNCH_SINGLE_TOP;
+import static android.content.pm.ActivityInfo.launchModeToString;
 import static android.content.pm.PackageManager.PERMISSION_GRANTED;
 import static android.os.Process.INVALID_UID;
 import static android.view.Display.DEFAULT_DISPLAY;
@@ -2071,8 +2072,20 @@ class ActivityStarter {
         }
 
         if (mInTaskFragment != null && !canEmbedActivity(mInTaskFragment, r, newTask, targetTask)) {
-            Slog.e(TAG, "Permission denied: Cannot embed " + r + " to " + mInTaskFragment.getTask()
-                    + " targetTask= " + targetTask);
+            final StringBuilder errorMsg = new StringBuilder("Permission denied: Cannot embed " + r
+                    + " to " + mInTaskFragment.getTask() + ". newTask=" + newTask + ", targetTask= "
+                    + targetTask);
+            if (newTask && isLaunchModeOneOf(LAUNCH_SINGLE_INSTANCE,
+                    LAUNCH_SINGLE_INSTANCE_PER_TASK, LAUNCH_SINGLE_TASK)) {
+                errorMsg.append("\nActivity tries to launch on a new task because the launch mode"
+                        + " is " + launchModeToString(mLaunchMode));
+            } else if (newTask && (mLaunchFlags & (FLAG_ACTIVITY_NEW_DOCUMENT
+                    | FLAG_ACTIVITY_NEW_TASK)) != 0) {
+                errorMsg.append("\nActivity tries to launch on a new task because the launch flags"
+                        + " contains FLAG_ACTIVITY_NEW_DOCUMENT or FLAG_ACTIVITY_NEW_TASK. "
+                        + "mLaunchFlag=" + mLaunchFlags);
+            }
+            Slog.e(TAG, errorMsg.toString());
             return START_PERMISSION_DENIED;
         }
 
@@ -3301,12 +3314,8 @@ class ActivityStarter {
             pw.println(mOptions);
         }
         pw.print(prefix);
-        pw.print("mLaunchSingleTop=");
-        pw.print(LAUNCH_SINGLE_TOP == mLaunchMode);
-        pw.print(" mLaunchSingleInstance=");
-        pw.print(LAUNCH_SINGLE_INSTANCE == mLaunchMode);
-        pw.print(" mLaunchSingleTask=");
-        pw.println(LAUNCH_SINGLE_TASK == mLaunchMode);
+        pw.print("mLaunchMode=");
+        pw.print(launchModeToString(mLaunchMode));
         pw.print(prefix);
         pw.print("mLaunchFlags=0x");
         pw.print(Integer.toHexString(mLaunchFlags));