From a7d6da803241d45aec5edb0e357be88afc862739 Mon Sep 17 00:00:00 2001
From: Siting Mo <siting.mo@oppo.corp-partner.google.com>
Date: Mon, 11 Jul 2022 15:32:25 +0800
Subject: [PATCH] Add AMS lock protection to mAppsInBackgroundRestricted
 collection

When the process is started asynchronously, the mAppsInBackgroundRestricted collection lacks AMS lock
protection and will throw ConcurrentModificationException
crash with a low probability.

Bug: 236582924
Test: Treehugger
Change-Id: Ieec1de9ee1fd336cf1de54566f80442e3cd3acdd
---
 services/core/java/com/android/server/am/ProcessList.java | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/services/core/java/com/android/server/am/ProcessList.java b/services/core/java/com/android/server/am/ProcessList.java
index 92a8dcd2ba8f3..98e3a214435a4 100644
--- a/services/core/java/com/android/server/am/ProcessList.java
+++ b/services/core/java/com/android/server/am/ProcessList.java
@@ -2269,7 +2269,9 @@ public final class ProcessList {
                 final boolean inBgRestricted = ast.isAppBackgroundRestricted(
                         app.info.uid, app.info.packageName);
                 if (inBgRestricted) {
-                    mAppsInBackgroundRestricted.add(app);
+                    synchronized (mService) {
+                        mAppsInBackgroundRestricted.add(app);
+                    }
                 }
                 app.mState.setBackgroundRestricted(inBgRestricted);
             }