From e4cf36fbd1ba3ec5e05c5df0421bb97b5f7f3ff0 Mon Sep 17 00:00:00 2001
From: Chong Zhang <chz@google.com>
Date: Fri, 3 Jun 2016 14:38:33 -0700
Subject: [PATCH] Check if task was top of stack before it's removed

To decide if home stack should be brought foreward. If the app is
finishing, it's no longer considered "running" and cleanUpActivityLocked
could move focus to the activity below. Then removeActivityFromHistoryLocked
would fail to bring front home stack as the removed task is no longer top.

bug: 29030518
Change-Id: I887e7c226258651d887cb0a4a6c6caab0a04e6e6
---
 .../com/android/server/am/ActivityStack.java  | 21 +++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/services/core/java/com/android/server/am/ActivityStack.java b/services/core/java/com/android/server/am/ActivityStack.java
index 4439a24a4b077..d83a750ccbb36 100644
--- a/services/core/java/com/android/server/am/ActivityStack.java
+++ b/services/core/java/com/android/server/am/ActivityStack.java
@@ -3764,7 +3764,8 @@ final class ActivityStack {
         r.finishLaunchTickingLocked();
     }
 
-    private void removeActivityFromHistoryLocked(ActivityRecord r, String reason) {
+    private void removeActivityFromHistoryLocked(
+            ActivityRecord r, TaskRecord oldTop, String reason) {
         mStackSupervisor.removeChildActivityContainers(r);
         finishActivityResultsLocked(r, Activity.RESULT_CANCELED, null);
         r.makeFinishingLocked();
@@ -3783,10 +3784,11 @@ final class ActivityStack {
             validateAppTokensLocked();
         }
         final TaskRecord task = r.task;
+        final TaskRecord topTask = oldTop != null ? oldTop : topTask();
         if (task != null && task.removeActivity(r)) {
             if (DEBUG_STACK) Slog.i(TAG_STACK,
                     "removeActivityFromHistoryLocked: last activity removed from " + this);
-            if (mStackSupervisor.isFocusedStack(this) && task == topTask() &&
+            if (mStackSupervisor.isFocusedStack(this) && task == topTask &&
                     task.isOverHomeStack()) {
                 mStackSupervisor.moveHomeStackTaskToTop(task.getTaskToReturnTo(), reason);
             }
@@ -3922,6 +3924,12 @@ final class ActivityStack {
 
         boolean removedFromHistory = false;
 
+        // If the activity is finishing, it's no longer considered in topRunningActivityLocked,
+        // and cleanUpActivityLocked() may change focus to another activity (or task).
+        // Get the current top task now, as removeActivityFromHistoryLocked() below need this
+        // to decide whether to return to home stack after removal.
+        final TaskRecord topTask = topTask();
+
         cleanUpActivityLocked(r, false, false);
 
         final boolean hadApp = r.app != null;
@@ -3956,7 +3964,8 @@ final class ActivityStack {
                 // up.
                 //Slog.w(TAG, "Exception thrown during finish", e);
                 if (r.finishing) {
-                    removeActivityFromHistoryLocked(r, reason + " exceptionInScheduleDestroy");
+                    removeActivityFromHistoryLocked(
+                            r, topTask, reason + " exceptionInScheduleDestroy");
                     removedFromHistory = true;
                     skipDestroy = true;
                 }
@@ -3987,7 +3996,7 @@ final class ActivityStack {
         } else {
             // remove this record from the history.
             if (r.finishing) {
-                removeActivityFromHistoryLocked(r, reason + " hadNoApp");
+                removeActivityFromHistoryLocked(r, topTask, reason + " hadNoApp");
                 removedFromHistory = true;
             } else {
                 if (DEBUG_STATES) Slog.v(TAG_STATES, "Moving to DESTROYED: " + r + " (no app)");
@@ -4018,7 +4027,7 @@ final class ActivityStack {
             if (isInStackLocked(r) != null) {
                 if (r.state == ActivityState.DESTROYING) {
                     cleanUpActivityLocked(r, true, false);
-                    removeActivityFromHistoryLocked(r, reason);
+                    removeActivityFromHistoryLocked(r, null, reason);
                 }
             }
             mStackSupervisor.resumeFocusedStackTopActivityLocked();
@@ -4176,7 +4185,7 @@ final class ActivityStack {
                     }
                     cleanUpActivityLocked(r, true, true);
                     if (remove) {
-                        removeActivityFromHistoryLocked(r, "appDied");
+                        removeActivityFromHistoryLocked(r, null, "appDied");
                     }
                 }
             }