From dbfdb3f58981c68d503c3d59d1381b13881acbb8 Mon Sep 17 00:00:00 2001
From: Neil Fuller <nfuller@google.com>
Date: Tue, 7 Mar 2023 14:06:39 +0000
Subject: [PATCH] Stop blocking broadcast receiver thread

Stop blocking broadcast receiver thread during network operations.

This reverts part of a behavior change from commit 6bb629bb088.
That commit switched a BroadcastReceiver over to using a specific
handler (X) for some long-running work. That isn't the same behavior as
posting the work to handler X and returning immediately, and it can
cause an ANR if the work takes too long.

The behavior has been changed back to explicitly post work to the
handler and return.

Bug: 271951363
Test: build / boot / treehugger
Change-Id: I9aeaf200d19de97b5be909678aab8d5421cd11a4
---
 .../NetworkTimeUpdateService.java             | 36 +++++++++++--------
 1 file changed, 22 insertions(+), 14 deletions(-)

diff --git a/services/core/java/com/android/server/timedetector/NetworkTimeUpdateService.java b/services/core/java/com/android/server/timedetector/NetworkTimeUpdateService.java
index 399e9413bded5..61386cbbc3782 100644
--- a/services/core/java/com/android/server/timedetector/NetworkTimeUpdateService.java
+++ b/services/core/java/com/android/server/timedetector/NetworkTimeUpdateService.java
@@ -30,7 +30,6 @@ import android.content.Intent;
 import android.content.IntentFilter;
 import android.database.ContentObserver;
 import android.net.ConnectivityManager;
-import android.net.ConnectivityManager.NetworkCallback;
 import android.net.Network;
 import android.os.Binder;
 import android.os.Handler;
@@ -140,20 +139,12 @@ public class NetworkTimeUpdateService extends Binder {
     /** Initialize the receivers and initiate the first NTP request */
     public void systemRunning() {
         // Listen for scheduled refreshes.
-        mContext.registerReceiver(
-                new BroadcastReceiver() {
-                    @Override
-                    public void onReceive(Context context, Intent intent) {
-                        onPollNetworkTime("scheduled refresh");
-                    }
-                },
-                new IntentFilter(ACTION_POLL),
-                /*broadcastPermission=*/ null,
-                mHandler);
+        ScheduledRefreshBroadcastReceiver receiver = new ScheduledRefreshBroadcastReceiver();
+        mContext.registerReceiver(receiver, new IntentFilter(ACTION_POLL));
 
         // Listen for network connectivity changes.
-        NetworkTimeUpdateCallback networkTimeUpdateCallback = new NetworkTimeUpdateCallback();
-        mCM.registerDefaultNetworkCallback(networkTimeUpdateCallback, mHandler);
+        NetworkConnectivityCallback networkConnectivityCallback = new NetworkConnectivityCallback();
+        mCM.registerDefaultNetworkCallback(networkConnectivityCallback, mHandler);
 
         // Listen for user settings changes.
         ContentResolver resolver = mContext.getContentResolver();
@@ -241,8 +232,25 @@ public class NetworkTimeUpdateService extends Binder {
         }
     }
 
+    private class ScheduledRefreshBroadcastReceiver extends BroadcastReceiver implements Runnable {
+
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            // The BroadcastReceiver has to complete quickly or an ANR will be triggered by the
+            // platform regardless of the receiver thread used. Instead of blocking the receiver
+            // thread, the long-running / blocking work is posted to mHandler to allow onReceive()
+            // to return immediately.
+            mHandler.post(this);
+        }
+
+        @Override
+        public void run() {
+            onPollNetworkTime("scheduled refresh");
+        }
+    }
+
     // All callbacks will be invoked using mHandler because of how the callback is registered.
-    private class NetworkTimeUpdateCallback extends NetworkCallback {
+    private class NetworkConnectivityCallback extends ConnectivityManager.NetworkCallback {
         @Override
         public void onAvailable(@NonNull Network network) {
             Log.d(TAG, String.format("New default network %s; checking time.", network));