[Magnifier-86] Fix deadlock causing ANR

"main" prio=5 tid=1 Blocked
  | group="main" sCount=1 dsCount=0 flags=1 obj=0x74aeca00 self=0x7021814c00
  | sysTid=27953 nice=-10 cgrp=default sched=0/0 handle=0x70a85ff548
  | state=S schedstat=( 31382082536 9164116362 28130 ) utm=2661 stm=477 core=0 HZ=100
  | stack=0x7ff7a52000-0x7ff7a54000 stackSize=8MB
  | held mutexes=
  at android.widget.Magnifier$InternalPopupWindow.destroy(Magnifier.java:607)
  - waiting to lock <0x0ef5c351> (a java.lang.Object) held by thread 13
  at android.widget.Magnifier.dismiss(Magnifier.java:191)
  - locked <0x01cd07b6> (a java.lang.Object)

 "hwuiTask1" prio=5 tid=13 Blocked
  | group="main" sCount=1 dsCount=0 flags=1 obj=0x12f815d8 self=0x70000e7800
  | sysTid=28075 nice=-2 cgrp=default sched=0/0 handle=0x70046ba4f0
  | state=S schedstat=( 138800095 85604746 532 ) utm=10 stm=3 core=1 HZ=100
  | stack=0x70045bf000-0x70045c1000 stackSize=1009KB
  | held mutexes=
  at android.widget.Magnifier$InternalPopupWindow.lambda$doDraw$0(Magnifier.java:663)
  - waiting to lock <0x01cd07b6> (a java.lang.Object) held by thread 1
  - locked <0x0ef5c351> (a java.lang.Object)
  at android.widget.-$$Lambda$Magnifier$InternalPopupWindow$vZThyvjDQhg2J1GAeOWCNqy2iiw.onFrameDraw(lambda:-1)

Bug: 133396461
Test: atest CtsWidgetTestCases:android.widget.cts.MagnifierTest
Change-Id: Idf0373ab0d5033d56da0f6f45d7d953f7e796813
Merged-In: Idf0373ab0d5033d56da0f6f45d7d953f7e796813

1 files changed, 12 insertions, 6 deletions

diff --git a/core/java/android/widget/Magnifier.java b/core/java/android/widget/Magnifier.java
index 08799cfb5d4c..cb5dc5f88b3e 100644
--- a/core/java/android/widget/Magnifier.java
+++ b/core/java/android/widget/Magnifier.java
@@ -136,6 +136,8 @@ public final class Magnifier {
     // Lock to synchronize between the UI thread and the thread that handles pixel copy results.
     // Only sync mWindow writes from UI thread with mWindow reads from sPixelCopyHandlerThread.
     private final Object mLock = new Object();
+    // The lock used to synchronize the UI and render threads when a #dismiss is performed.
+    private final Object mDestroyLock = new Object();
 
     /**
      * Initializes a magnifier.
@@ -275,7 +277,7 @@ public final class Magnifier {
                             mWindowElevation, mWindowCornerRadius,
                             mOverlay != null ? mOverlay : new ColorDrawable(Color.TRANSPARENT),
                             Handler.getMain() /* draw the magnifier on the UI thread */, mLock,
-                            mCallback);
+                            mDestroyLock, mCallback);
                 }
             }
             performPixelCopy(startX, startY, true /* update window position */);
@@ -304,9 +306,11 @@ public final class Magnifier {
      */
     public void dismiss() {
         if (mWindow != null) {
-            synchronized (mLock) {
-                mWindow.destroy();
-                mWindow = null;
+            synchronized (mDestroyLock) {
+                synchronized (mLock) {
+                    mWindow.destroy();
+                    mWindow = null;
+                }
             }
             mPrevShowSourceCoords.x = NONEXISTENT_PREVIOUS_CONFIG_VALUE;
             mPrevShowSourceCoords.y = NONEXISTENT_PREVIOUS_CONFIG_VALUE;
@@ -819,7 +823,7 @@ public final class Magnifier {
         // is performed on the UI thread and a frame callback on the render thread.
         // When both mLock and mDestroyLock need to be held at the same time,
         // mDestroyLock should be acquired before mLock in order to avoid deadlocks.
-        private final Object mDestroyLock = new Object();
+        private final Object mDestroyLock;
 
         // The current content of the magnifier. It is mBitmap + mOverlay, only used for testing.
         private Bitmap mCurrentContent;
@@ -827,10 +831,12 @@ public final class Magnifier {
         InternalPopupWindow(final Context context, final Display display,
                 final SurfaceControl parentSurfaceControl, final int width, final int height,
                 final float elevation, final float cornerRadius, final Drawable overlay,
-                final Handler handler, final Object lock, final Callback callback) {
+                final Handler handler, final Object lock, final Object destroyLock,
+                final Callback callback) {
             mDisplay = display;
             mOverlay = overlay;
             mLock = lock;
+            mDestroyLock = destroyLock;
             mCallback = callback;
 
             mContentWidth = width;