From 59e85c25a65b9d89855de9366fef499003a65e29 Mon Sep 17 00:00:00 2001
From: Louis Chang <louischang@google.com>
Date: Thu, 5 Dec 2019 16:22:57 +0800
Subject: [PATCH] Add warning message when entering loop twice

The messages in queue could be executed before current
message completed.

Bug: 140599188
Test: calling Looper.loop() twice
Change-Id: I1a4628606ed974e7a6a76b2832044959a9261bb9
---
 core/java/android/os/Looper.java | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/core/java/android/os/Looper.java b/core/java/android/os/Looper.java
index b478dbe2555d5..a7e326378228d 100644
--- a/core/java/android/os/Looper.java
+++ b/core/java/android/os/Looper.java
@@ -77,6 +77,7 @@ public final class Looper {
     @UnsupportedAppUsage
     final MessageQueue mQueue;
     final Thread mThread;
+    private boolean mInLoop;
 
     @UnsupportedAppUsage
     private Printer mLogging;
@@ -155,6 +156,12 @@ public final class Looper {
         if (me == null) {
             throw new RuntimeException("No Looper; Looper.prepare() wasn't called on this thread.");
         }
+        if (me.mInLoop) {
+            Slog.w(TAG, "Loop again would have the queued messages be executed"
+                    + " before this one completed.");
+        }
+
+        me.mInLoop = true;
         final MessageQueue queue = me.mQueue;
 
         // Make sure the identity of this thread is that of the local process,