Fix the issue of accessing BrightnessSetting inside a lock

Given BrightnessSetting is operating on the display lock, acquiring
power lock while accessing the BrightnessSetting can result in a
deadlock.

Bug: 278692011
Test: Manually verified the behaviour is intact
Test: atest DisplayBrightnessControllerTest
Change-Id: I40c8340895c165da3b96015bc3e8918c259876ac

services/core/java/com/android/server/display/brightness/DisplayBrightnessController.java

@@ -437,6 +437,7 @@ public final class DisplayBrightnessController {
      * persist the nit value, the nit value for the default display will be loaded.
      */
     private void loadNitBasedBrightnessSetting() {
+        float currentBrightnessSetting = Float.NaN;
         if (mDisplayId == Display.DEFAULT_DISPLAY && mPersistBrightnessNitsForDefaultDisplay) {
             float brightnessNitsForDefaultDisplay =
                     mBrightnessSetting.getBrightnessNitsForDefaultDisplay();
@@ -445,15 +446,17 @@ public final class DisplayBrightnessController {
                         brightnessNitsForDefaultDisplay);
                 if (BrightnessUtils.isValidBrightnessValue(brightnessForDefaultDisplay)) {
                     mBrightnessSetting.setBrightness(brightnessForDefaultDisplay);
-                    synchronized (mLock) {
-                        mCurrentScreenBrightness = brightnessForDefaultDisplay;
-                    }
-                    return;
+                    currentBrightnessSetting = brightnessForDefaultDisplay;
                 }
             }
         }
+
+        if (Float.isNaN(currentBrightnessSetting)) {
+            currentBrightnessSetting = getScreenBrightnessSetting();
+        }
+
         synchronized (mLock) {
-            mCurrentScreenBrightness = getScreenBrightnessSetting();
+            mCurrentScreenBrightness = currentBrightnessSetting;
         }
     }
 }

services/tests/servicestests/src/com/android/server/display/brightness/DisplayBrightnessControllerTest.java

@@ -19,10 +19,13 @@ package com.android.server.display.brightness;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.clearInvocations;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.verifyZeroInteractions;
 import static org.mockito.Mockito.when;
 
 import android.content.Context;
@@ -66,25 +69,27 @@ public final class DisplayBrightnessControllerTest {
     @Mock
     private HandlerExecutor mBrightnessChangeExecutor;
 
+    private final DisplayBrightnessController.Injector mInjector = new
+            DisplayBrightnessController.Injector() {
+        @Override
+        DisplayBrightnessStrategySelector getDisplayBrightnessStrategySelector(
+                Context context, int displayId) {
+            return mDisplayBrightnessStrategySelector;
+        }
+    };
+
     private DisplayBrightnessController mDisplayBrightnessController;
 
     @Before
     public void before() {
         MockitoAnnotations.initMocks(this);
         when(mContext.getResources()).thenReturn(mResources);
-        DisplayBrightnessController.Injector injector = new DisplayBrightnessController.Injector() {
-            @Override
-            DisplayBrightnessStrategySelector getDisplayBrightnessStrategySelector(
-                    Context context, int displayId) {
-                return mDisplayBrightnessStrategySelector;
-            }
-        };
         when(mBrightnessSetting.getBrightness()).thenReturn(Float.NaN);
         when(mBrightnessSetting.getBrightnessNitsForDefaultDisplay()).thenReturn(-1f);
         when(mResources.getBoolean(
                 com.android.internal.R.bool.config_persistBrightnessNitsForDefaultDisplay))
                 .thenReturn(true);
-        mDisplayBrightnessController = new DisplayBrightnessController(mContext, injector,
+        mDisplayBrightnessController = new DisplayBrightnessController(mContext, mInjector,
                 DISPLAY_ID, DEFAULT_BRIGHTNESS, mBrightnessSetting, mOnBrightnessChangeRunnable,
                 mBrightnessChangeExecutor);
     }
@@ -256,27 +261,6 @@ public final class DisplayBrightnessControllerTest {
         verifyNoMoreInteractions(mBrightnessChangeExecutor, mBrightnessSetting);
     }
 
-    @Test
-    public void testBrightnessNitsForDefaultDisplay() {
-        float brightness = 0.3f;
-        float nits = 500;
-        AutomaticBrightnessController automaticBrightnessController =
-                mock(AutomaticBrightnessController.class);
-        when(automaticBrightnessController.convertToFloatScale(nits)).thenReturn(brightness);
-        when(mBrightnessSetting.getBrightnessNitsForDefaultDisplay()).thenReturn(nits);
-
-        mDisplayBrightnessController.setAutomaticBrightnessController(
-                automaticBrightnessController);
-        assertEquals(brightness, mDisplayBrightnessController.getCurrentBrightness(),
-                /* delta= */ 0);
-
-        float newBrightness = 0.5f;
-        float newNits = 700;
-        when(automaticBrightnessController.convertToNits(newBrightness)).thenReturn(newNits);
-        mDisplayBrightnessController.setBrightness(newBrightness);
-        verify(mBrightnessSetting).setBrightnessNitsForDefaultDisplay(newNits);
-    }
-
     @Test
     public void testConvertToNits() {
         final float brightness = 0.5f;
@@ -330,4 +314,48 @@ public final class DisplayBrightnessControllerTest {
         mDisplayBrightnessController.stop();
         verify(mBrightnessSetting).unregisterListener(brightnessSettingListener);
     }
+
+    @Test
+    public void testLoadNitBasedBrightnessSetting() {
+        // When the nits value is valid, the brightness is set from the old default display nits
+        // value
+        float nits = 200f;
+        float brightness = 0.3f;
+        AutomaticBrightnessController automaticBrightnessController =
+                mock(AutomaticBrightnessController.class);
+        when(automaticBrightnessController.convertToFloatScale(nits)).thenReturn(brightness);
+        when(mBrightnessSetting.getBrightnessNitsForDefaultDisplay()).thenReturn(nits);
+        mDisplayBrightnessController.setAutomaticBrightnessController(
+                automaticBrightnessController);
+        verify(mBrightnessSetting).setBrightness(brightness);
+        assertEquals(brightness, mDisplayBrightnessController.getCurrentBrightness(), 0.01f);
+        clearInvocations(automaticBrightnessController, mBrightnessSetting);
+
+        // When the nits value is invalid, the brightness is resumed from where it was last set
+        nits = -1;
+        brightness = 0.4f;
+        when(automaticBrightnessController.convertToFloatScale(nits)).thenReturn(brightness);
+        when(mBrightnessSetting.getBrightnessNitsForDefaultDisplay()).thenReturn(nits);
+        when(mBrightnessSetting.getBrightness()).thenReturn(brightness);
+        mDisplayBrightnessController.setAutomaticBrightnessController(
+                automaticBrightnessController);
+        verify(mBrightnessSetting, never()).setBrightness(brightness);
+        assertEquals(brightness, mDisplayBrightnessController.getCurrentBrightness(), 0.01f);
+        clearInvocations(automaticBrightnessController, mBrightnessSetting);
+
+        // When the display is a non-default display, the brightness is resumed from where it was
+        // last set
+        int nonDefaultDisplayId = 1;
+        mDisplayBrightnessController = new DisplayBrightnessController(mContext, mInjector,
+                nonDefaultDisplayId, DEFAULT_BRIGHTNESS, mBrightnessSetting,
+                mOnBrightnessChangeRunnable, mBrightnessChangeExecutor);
+        brightness = 0.5f;
+        when(mBrightnessSetting.getBrightness()).thenReturn(brightness);
+        mDisplayBrightnessController.setAutomaticBrightnessController(
+                automaticBrightnessController);
+        assertEquals(brightness, mDisplayBrightnessController.getCurrentBrightness(), 0.01f);
+        verifyZeroInteractions(automaticBrightnessController);
+        verify(mBrightnessSetting, never()).getBrightnessNitsForDefaultDisplay();
+        verify(mBrightnessSetting, never()).setBrightness(brightness);
+    }
 }