fix(magnifier): fix deadlock when feature flag changes

Handle feature flag changes on a background thread so we're not blocking
the main thread which might already be locked.

Fix: 281132229
Test: 0. Complete initial SUW without connecting WiFi, no account added and no lock screen set.
1. On target device, tap on deferred SUW notification and proceed.
2. Tap on "Get started" on Welcome screen. Quick Start User Guide screen is displayed.
3. Connect source and target devices by scanning the QR Code with scanner
4. WiFi setting is transferred and the target device connected to internet. Getting your phone ready screen is shown
6. Wait and observe. SysUi should not hang / black screen.

Change-Id: Ic2cf5cfb34041671468f0036a243e24005d064c9

services/accessibility/java/com/android/server/accessibility/AccessibilityManagerService.java

@@ -179,6 +179,7 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.Executors;
 import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.function.Predicate;
@@ -494,8 +495,13 @@ public class AccessibilityManagerService extends IAccessibilityManager.Stub
         mA11yWindowManager = new AccessibilityWindowManager(mLock, mMainHandler,
                 mWindowManagerService, this, mSecurityPolicy, this, mTraceManager);
         mA11yDisplayListener = new AccessibilityDisplayListener(mContext, mMainHandler);
-        mMagnificationController = new MagnificationController(this, mLock, mContext,
-                new MagnificationScaleProvider(mContext));
+        mMagnificationController = new MagnificationController(
+                this,
+                mLock,
+                mContext,
+                new MagnificationScaleProvider(mContext),
+                Executors.newSingleThreadExecutor()
+        );
         mMagnificationProcessor = new MagnificationProcessor(mMagnificationController);
         mCaptioningManagerImpl = new CaptioningManagerImpl(mContext);
         mProxyManager = new ProxyManager(mLock, mA11yWindowManager, mContext, mMainHandler,

services/accessibility/java/com/android/server/accessibility/magnification/FullScreenMagnificationController.java

@@ -56,7 +56,6 @@ import com.android.internal.R;
 import com.android.internal.accessibility.common.MagnificationConstants;
 import com.android.internal.annotations.GuardedBy;
 import com.android.internal.annotations.VisibleForTesting;
-import com.android.internal.util.ConcurrentUtils;
 import com.android.internal.util.function.pooled.PooledLambda;
 import com.android.server.LocalServices;
 import com.android.server.accessibility.AccessibilityManagerService;
@@ -65,6 +64,7 @@ import com.android.server.wm.WindowManagerInternal;
 
 import java.util.ArrayList;
 import java.util.Locale;
+import java.util.concurrent.Executor;
 import java.util.function.Supplier;
 
 /**
@@ -774,7 +774,8 @@ public class FullScreenMagnificationController implements
     public FullScreenMagnificationController(@NonNull Context context,
             @NonNull AccessibilityTraceManager traceManager, @NonNull Object lock,
             @NonNull MagnificationInfoChangedCallback magnificationInfoChangedCallback,
-            @NonNull MagnificationScaleProvider scaleProvider) {
+            @NonNull MagnificationScaleProvider scaleProvider,
+            @NonNull Executor backgroundExecutor) {
         this(
                 new ControllerContext(
                         context,
@@ -785,7 +786,8 @@ public class FullScreenMagnificationController implements
                 lock,
                 magnificationInfoChangedCallback,
                 scaleProvider,
-                /* thumbnailSupplier= */ null);
+                /* thumbnailSupplier= */ null,
+                backgroundExecutor);
     }
 
     /** Constructor for tests */
@@ -795,7 +797,8 @@ public class FullScreenMagnificationController implements
             @NonNull Object lock,
             @NonNull MagnificationInfoChangedCallback magnificationInfoChangedCallback,
             @NonNull MagnificationScaleProvider scaleProvider,
-            Supplier<MagnificationThumbnail> thumbnailSupplier) {
+            Supplier<MagnificationThumbnail> thumbnailSupplier,
+            @NonNull Executor backgroundExecutor) {
         mControllerCtx = ctx;
         mLock = lock;
         mMainThreadId = mControllerCtx.getContext().getMainLooper().getThread().getId();
@@ -805,7 +808,7 @@ public class FullScreenMagnificationController implements
         mDisplayManagerInternal = LocalServices.getService(DisplayManagerInternal.class);
         mMagnificationThumbnailFeatureFlag = new MagnificationThumbnailFeatureFlag();
         mMagnificationThumbnailFeatureFlag.addOnChangedListener(
-                ConcurrentUtils.DIRECT_EXECUTOR, this::onMagnificationThumbnailFeatureFlagChanged);
+                backgroundExecutor, this::onMagnificationThumbnailFeatureFlagChanged);
         if (thumbnailSupplier != null) {
             mThumbnailSupplier = thumbnailSupplier;
         } else {

services/accessibility/java/com/android/server/accessibility/magnification/MagnificationController.java

@@ -23,7 +23,6 @@ import static android.provider.Settings.Secure.ACCESSIBILITY_MAGNIFICATION_MODE_
 import static android.provider.Settings.Secure.ACCESSIBILITY_MAGNIFICATION_MODE_FULLSCREEN;
 import static android.provider.Settings.Secure.ACCESSIBILITY_MAGNIFICATION_MODE_NONE;
 import static android.provider.Settings.Secure.ACCESSIBILITY_MAGNIFICATION_MODE_WINDOW;
-import static android.view.accessibility.MagnificationAnimationCallback.STUB_ANIMATION_CALLBACK;
 
 import static com.android.server.accessibility.AccessibilityManagerService.MAGNIFICATION_GESTURE_HANDLER_ID;
 
@@ -48,11 +47,12 @@ import android.view.accessibility.MagnificationAnimationCallback;
 import com.android.internal.accessibility.util.AccessibilityStatsLogUtils;
 import com.android.internal.annotations.GuardedBy;
 import com.android.internal.annotations.VisibleForTesting;
-import com.android.internal.util.ConcurrentUtils;
 import com.android.server.LocalServices;
 import com.android.server.accessibility.AccessibilityManagerService;
 import com.android.server.wm.WindowManagerInternal;
 
+import java.util.concurrent.Executor;
+
 /**
  * Handles all magnification controllers initialization, generic interactions,
  * magnification mode transition and magnification switch UI show/hide logic
@@ -101,6 +101,8 @@ public class MagnificationController implements WindowMagnificationManager.Callb
     /** Whether the platform supports window magnification feature. */
     private final boolean mSupportWindowMagnification;
 
+    private final Executor mBackgroundExecutor;
+
     @GuardedBy("mLock")
     private final SparseIntArray mCurrentMagnificationModeArray = new SparseIntArray();
     @GuardedBy("mLock")
@@ -142,11 +144,13 @@ public class MagnificationController implements WindowMagnificationManager.Callb
     }
 
     public MagnificationController(AccessibilityManagerService ams, Object lock,
-            Context context, MagnificationScaleProvider scaleProvider) {
+            Context context, MagnificationScaleProvider scaleProvider,
+            Executor backgroundExecutor) {
         mAms = ams;
         mLock = lock;
         mContext = context;
         mScaleProvider = scaleProvider;
+        mBackgroundExecutor = backgroundExecutor;
         LocalServices.getService(WindowManagerInternal.class)
                 .getAccessibilityController().setUiChangesForAccessibilityCallbacks(this);
         mSupportWindowMagnification = context.getPackageManager().hasSystemFeature(
@@ -154,15 +158,15 @@ public class MagnificationController implements WindowMagnificationManager.Callb
 
         mAlwaysOnMagnificationFeatureFlag = new AlwaysOnMagnificationFeatureFlag();
         mAlwaysOnMagnificationFeatureFlag.addOnChangedListener(
-                ConcurrentUtils.DIRECT_EXECUTOR, mAms::updateAlwaysOnMagnification);
+                mBackgroundExecutor, mAms::updateAlwaysOnMagnification);
     }
 
     @VisibleForTesting
     public MagnificationController(AccessibilityManagerService ams, Object lock,
             Context context, FullScreenMagnificationController fullScreenMagnificationController,
             WindowMagnificationManager windowMagnificationManager,
-            MagnificationScaleProvider scaleProvider) {
-        this(ams, lock, context, scaleProvider);
+            MagnificationScaleProvider scaleProvider, Executor backgroundExecutor) {
+        this(ams, lock, context, scaleProvider, backgroundExecutor);
         mFullScreenMagnificationController = fullScreenMagnificationController;
         mWindowMagnificationMgr = windowMagnificationManager;
     }
@@ -757,8 +761,14 @@ public class MagnificationController implements WindowMagnificationManager.Callb
     public FullScreenMagnificationController getFullScreenMagnificationController() {
         synchronized (mLock) {
             if (mFullScreenMagnificationController == null) {
-                mFullScreenMagnificationController = new FullScreenMagnificationController(mContext,
-                        mAms.getTraceManager(), mLock, this, mScaleProvider);
+                mFullScreenMagnificationController = new FullScreenMagnificationController(
+                        mContext,
+                        mAms.getTraceManager(),
+                        mLock,
+                        this,
+                        mScaleProvider,
+                        mBackgroundExecutor
+                );
             }
         }
         return mFullScreenMagnificationController;

services/accessibility/java/com/android/server/accessibility/magnification/MagnificationFeatureFlagBase.java

@@ -80,6 +80,9 @@ abstract class MagnificationFeatureFlagBase {
      *
      * <p>{@see DeviceConfig#addOnPropertiesChangedListener(
      * String, Executor, DeviceConfig.OnPropertiesChangedListener)}
+     *
+     * <p>Note: be weary of using a DIRECT_EXECUTOR here. You may run into deadlocks! (see
+     * b/281132229)
      */
     @NonNull
     public DeviceConfig.OnPropertiesChangedListener addOnChangedListener(

services/tests/servicestests/src/com/android/server/accessibility/magnification/FullScreenMagnificationControllerTest.java

@@ -60,6 +60,7 @@ import android.view.accessibility.MagnificationAnimationCallback;
 import androidx.test.InstrumentationRegistry;
 import androidx.test.runner.AndroidJUnit4;
 
+import com.android.internal.util.ConcurrentUtils;
 import com.android.internal.util.test.FakeSettingsProvider;
 import com.android.server.LocalServices;
 import com.android.server.accessibility.AccessibilityTraceManager;
@@ -160,7 +161,8 @@ public class FullScreenMagnificationControllerTest {
                         new Object(),
                         mRequestObserver,
                         mScaleProvider,
-                        () -> mMockThumbnail);
+                        () -> mMockThumbnail,
+                        ConcurrentUtils.DIRECT_EXECUTOR);
     }
 
     @After

services/tests/servicestests/src/com/android/server/accessibility/magnification/FullScreenMagnificationGestureHandlerTest.java

@@ -54,6 +54,7 @@ import android.view.ViewConfiguration;
 
 import androidx.test.runner.AndroidJUnit4;
 
+import com.android.internal.util.ConcurrentUtils;
 import com.android.server.accessibility.AccessibilityManagerService;
 import com.android.server.accessibility.AccessibilityTraceManager;
 import com.android.server.accessibility.EventStreamTransformation;
@@ -170,8 +171,8 @@ public class FullScreenMagnificationGestureHandlerTest {
                 new Object(),
                 mMagnificationInfoChangedCallback,
                 new MagnificationScaleProvider(mContext),
-                () -> null
-        ) {
+                () -> null,
+                ConcurrentUtils.DIRECT_EXECUTOR) {
             @Override
             public boolean magnificationRegionContains(int displayId, float x, float y) {
                 return true;

services/tests/servicestests/src/com/android/server/accessibility/magnification/MagnificationControllerTest.java

@@ -64,6 +64,7 @@ import androidx.annotation.NonNull;
 import androidx.test.InstrumentationRegistry;
 import androidx.test.runner.AndroidJUnit4;
 
+import com.android.internal.util.ConcurrentUtils;
 import com.android.internal.util.test.FakeSettingsProvider;
 import com.android.server.LocalServices;
 import com.android.server.accessibility.AccessibilityManagerService;
@@ -199,7 +200,8 @@ public class MagnificationControllerTest {
                 new Object(),
                 mScreenMagnificationInfoChangedCallbackDelegate,
                 mScaleProvider,
-                () -> null
+                () -> null,
+                ConcurrentUtils.DIRECT_EXECUTOR
         ));
         mScreenMagnificationController.register(TEST_DISPLAY);
 
@@ -209,7 +211,8 @@ public class MagnificationControllerTest {
         mWindowMagnificationManager.setConnection(mMockConnection.getConnection());
 
         mMagnificationController = spy(new MagnificationController(mService, globalLock, mContext,
-                mScreenMagnificationController, mWindowMagnificationManager, mScaleProvider));
+                mScreenMagnificationController, mWindowMagnificationManager, mScaleProvider,
+                ConcurrentUtils.DIRECT_EXECUTOR));
         mMagnificationController.setMagnificationCapabilities(
                 Settings.Secure.ACCESSIBILITY_MAGNIFICATION_MODE_ALL);