From 1be9657cc4256e3ae1d09c5e9d78bea7aca5ffee Mon Sep 17 00:00:00 2001
From: Charles Chen <charlesccchen@google.com>
Date: Thu, 19 Aug 2021 22:49:02 +0800
Subject: [PATCH] Using LaunchActivity when possible

... to prevent race

In [1], we store ActivityClientRecord earlier to make
ActivityClientRecord accessible in onCreate Lifcycle callback.
However, we still store the activity after Activity#onCreate.

This CL fixes the exception by obtaining ActivityClientRecord
from launch Activity list first to prevent race.

fixes: 196900007
Test: Try reproducible steps several times and didn't see
the error log.

[1]: 85986bf974ceba929de1bfda6a7e43330e17595e

Change-Id: I7553c56cad474feb73fca73c72b5e6e833b46fbf
---
 .../ActivityTransactionItem.java              | 31 ++++++++++---------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/core/java/android/app/servertransaction/ActivityTransactionItem.java b/core/java/android/app/servertransaction/ActivityTransactionItem.java
index a539812fa8c6a..186f25deab67e 100644
--- a/core/java/android/app/servertransaction/ActivityTransactionItem.java
+++ b/core/java/android/app/servertransaction/ActivityTransactionItem.java
@@ -59,36 +59,37 @@ public abstract class ActivityTransactionItem extends ClientTransactionItem {
     }
 
     /**
-     * Get the {@link ActivityClientRecord} instance that corresponds to the provided token.
+     * Gets the {@link ActivityClientRecord} instance that corresponds to the provided token.
      * @param client Target client handler.
      * @param token Target activity token.
-     * @param includeLaunching Indicate to also find the {@link ActivityClientRecord} in launching
-     *                         activity list. It should be noted that there is no activity in
+     * @param includeLaunching Indicate to find the {@link ActivityClientRecord} in launching
+     *                         activity list.
+     *                         <p>Note that there is no {@link android.app.Activity} instance in
      *                         {@link ActivityClientRecord} from the launching activity list.
      * @return The {@link ActivityClientRecord} instance that corresponds to the provided token.
      */
     @NonNull ActivityClientRecord getActivityClientRecord(
             @NonNull ClientTransactionHandler client, IBinder token, boolean includeLaunching) {
-        ActivityClientRecord r = client.getActivityClient(token);
-        if (r != null) {
-            if (client.getActivity(token) == null) {
+        ActivityClientRecord r = null;
+        // Check launching Activity first to prevent race condition that activity instance has not
+        // yet set to ActivityClientRecord.
+        if (includeLaunching) {
+            r = client.getLaunchingActivity(token);
+        }
+        // Then if we don't want to find launching Activity or the ActivityClientRecord doesn't
+        // exist in launching Activity list. The ActivityClientRecord should have been initialized
+        // and put in the Activity list.
+        if (r == null) {
+            r = client.getActivityClient(token);
+            if (r != null && client.getActivity(token) == null) {
                 throw new IllegalArgumentException("Activity must not be null to execute "
                         + "transaction item");
             }
-            return r;
-        }
-        // The activity may not be launched yet. Fallback to check launching activity.
-        if (includeLaunching) {
-            r = client.getLaunchingActivity(token);
         }
         if (r == null) {
             throw new IllegalArgumentException("Activity client record must not be null to execute "
                     + "transaction item");
         }
-
-        // We don't need to check the activity of launching activity client records because they
-        // have not been launched yet.
-
         return r;
     }
 }