Return the correct root task when start activity from recents

When starting activity from recents, the system will find the
suitable task and move it to the front.  With corresponding task
display area, TDA#getOrCreateRootTask returns the candidate task
directly instead of the existing launch root task.
In RootWindowContainer#anyTaskForId, the candidate task is reparent
to the root task(same as itself) which resolve from the
TDA#getOrCreateRootTask and lead to the watchdog timeout. This CL
updates the logic to return the correct root task.

Bug: 197293995
Test: atest MultiWindowTests,WMShellUnitTests
Change-Id: Ib0b24363dc35d624c358080998c25874d9e7094c

2 files changed, 13 insertions, 11 deletions

diff --git a/services/core/java/com/android/server/wm/TaskDisplayArea.java b/services/core/java/com/android/server/wm/TaskDisplayArea.java
index c7ca180bfa14..4a1a922c8a02 100644
--- a/services/core/java/com/android/server/wm/TaskDisplayArea.java
+++ b/services/core/java/com/android/server/wm/TaskDisplayArea.java
@@ -1095,29 +1095,27 @@ final class TaskDisplayArea extends DisplayArea<WindowContainer> {
                 return rootTask;
             }
         } else if (candidateTask != null) {
-            final Task rootTask = candidateTask;
             final int position = onTop ? POSITION_TOP : POSITION_BOTTOM;
             final Task launchRootTask = getLaunchRootTask(windowingMode, activityType, options,
                     sourceTask, launchFlags);
-
             if (launchRootTask != null) {
-                if (rootTask.getParent() == null) {
-                    launchRootTask.addChild(rootTask, position);
-                } else if (rootTask.getParent() != launchRootTask) {
-                    rootTask.reparent(launchRootTask, position);
+                if (candidateTask.getParent() == null) {
+                    launchRootTask.addChild(candidateTask, position);
+                } else if (candidateTask.getParent() != launchRootTask) {
+                    candidateTask.reparent(launchRootTask, position);
                 }
-            } else if (rootTask.getDisplayArea() != this || !rootTask.isRootTask()) {
-                if (rootTask.getParent() == null) {
-                    addChild(rootTask, position);
+            } else if (candidateTask.getDisplayArea() != this || !candidateTask.isRootTask()) {
+                if (candidateTask.getParent() == null) {
+                    addChild(candidateTask, position);
                 } else {
-                    rootTask.reparent(this, onTop);
+                    candidateTask.reparent(this, onTop);
                 }
             }
             // Update windowing mode if necessary, e.g. moving a pinned task to fullscreen.
             if (candidateTask.getWindowingMode() != windowingMode) {
                 candidateTask.setWindowingMode(windowingMode);
             }
-            return rootTask;
+            return candidateTask.getRootTask();
         }
         return new Task.Builder(mAtmService)
                 .setWindowingMode(windowingMode)
diff --git a/services/core/java/com/android/server/wm/WindowContainer.java b/services/core/java/com/android/server/wm/WindowContainer.java
index 2882a2391066..cdfa5aa84a95 100644
--- a/services/core/java/com/android/server/wm/WindowContainer.java
+++ b/services/core/java/com/android/server/wm/WindowContainer.java
@@ -354,6 +354,10 @@ class WindowContainer<E extends WindowContainer> extends ConfigurationContainer<
             throw new IllegalArgumentException("reparent: can't reparent to null " + this);
         }
 
+        if (newParent == this) {
+            throw new IllegalArgumentException("Can not reparent to itself " + this);
+        }
+
         final WindowContainer oldParent = mParent;
         if (mParent == newParent) {
             throw new IllegalArgumentException("WC=" + this + " already child of " + mParent);