From ab7c9c006528efd0a2651b612bdcc0467064e592 Mon Sep 17 00:00:00 2001
From: Santos Cordon <santoscordon@google.com>
Date: Wed, 15 Dec 2021 13:46:57 +0000
Subject: [PATCH] Fix potential deadlock with SensorObserver.

Sensor Observer grabs it's own lock (mSOLock) when voting for a display
mode, which then grabs the global DMD lock (mLock).
When printing out the dump() method, DMD holds mLock, then calls into
SensorObserver which grabs the mSOLock.  This can cause a deadlock.

There's no reason to hold mLock when calling SensorObserver's dump()
method, so fix that.

Test: adb shell dumpsys display
Bug: 210086128
Change-Id: Idf685f94b818f04f30bee5b85a503f64d448291a
(cherry picked from commit 8f808c5d7954215d846a4fca227e53dd33dd3428)
---
 .../com/android/server/display/DisplayModeDirector.java     | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/services/core/java/com/android/server/display/DisplayModeDirector.java b/services/core/java/com/android/server/display/DisplayModeDirector.java
index 0a22f2fdfdf8e..a4f7c85dee29b 100644
--- a/services/core/java/com/android/server/display/DisplayModeDirector.java
+++ b/services/core/java/com/android/server/display/DisplayModeDirector.java
@@ -41,7 +41,6 @@ import android.os.IThermalEventListener;
 import android.os.IThermalService;
 import android.os.Looper;
 import android.os.Message;
-import android.os.PowerManager;
 import android.os.RemoteException;
 import android.os.ServiceManager;
 import android.os.SystemClock;
@@ -618,10 +617,11 @@ public class DisplayModeDirector {
             mAppRequestObserver.dumpLocked(pw);
             mBrightnessObserver.dumpLocked(pw);
             mUdfpsObserver.dumpLocked(pw);
-            mSensorObserver.dumpLocked(pw);
             mHbmObserver.dumpLocked(pw);
             mSkinThermalStatusObserver.dumpLocked(pw);
         }
+
+        mSensorObserver.dump(pw);
     }
 
     private void updateVoteLocked(int priority, Vote vote) {
@@ -2241,7 +2241,7 @@ public class DisplayModeDirector {
             }
         }
 
-        void dumpLocked(PrintWriter pw) {
+        void dump(PrintWriter pw) {
             pw.println("  SensorObserver");
             synchronized (mSensorObserverLock) {
                 pw.println("    mIsProxActive=" + mIsProxActive);