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Commit 5393aa51 authored by Danny Baumann's avatar Danny Baumann
Browse files

Fix race condition in backlight adjustment. 

When configuring the automatic backlight levels, there's a race
condition in setting the lux and brightness settings as the settings
provider doesn't allow storing multiple settings atomically. When
deleting rows, there's quite a high chance of DisplayPowerController
picking up a state where the lux values already have the lower number of
rows, but the brightness values do not, effectively leading to an
ArrayIndexOutOfBoundsException.

Fix that by
- waiting a second of cool-down time until applying the settings and
- adding a sanity check for the very unlikely case that the delay
  between writing both values is > 1 second

Change-Id: I44e41530fc5334aaefc4ab7d3a90542f78fabe0c
JIRA:CYAN-755
parent 2e939f9d

services/java/com/android/server/power/DisplayPowerController.java

+16 −3
Original line number Diff line number Diff line
@@ -118,6 +118,7 @@ final class DisplayPowerController { 
    private static final int MSG_UPDATE_POWER_STATE = 1;

    private static final int MSG_PROXIMITY_SENSOR_DEBOUNCED = 2;

    private static final int MSG_LIGHT_SENSOR_DEBOUNCED = 3;

    private static final int MSG_UPDATE_BACKLIGHT_SETTINGS = 4;



    private static final int PROXIMITY_UNKNOWN = -1;

    private static final int PROXIMITY_NEGATIVE = 0;
@@ -390,9 +391,11 @@ final class DisplayPowerController { 
            final ContentObserver observer = new ContentObserver(mHandler) {

                @Override

                public void onChange(boolean selfChange, Uri uri) {

                    mAutoBrightnessSettingsChanged = true;

                    updateAutomaticBrightnessSettings();

                    updatePowerState();

                    // As both LUX and BACKLIGHT might be changed at the same time, there's

                    // a potential race condition. As the settings provider API doesn't give

                    // us transactions to avoid them, wait a little until things settle down

                    mHandler.removeMessages(MSG_UPDATE_BACKLIGHT_SETTINGS);

                    mHandler.sendEmptyMessageDelayed(MSG_UPDATE_BACKLIGHT_SETTINGS, 1000);

                }

            };
@@ -486,6 +489,10 @@ final class DisplayPowerController { 
    }



    private static Spline createAutoBrightnessSpline(int[] lux, int[] brightness) {

        if (lux.length < 2 || lux.length != (brightness.length - 1)) {

            return null;

        }



        try {

            final int n = brightness.length;

            float[] x = new float[n];
@@ -1361,6 +1368,12 @@ final class DisplayPowerController { 
                case MSG_LIGHT_SENSOR_DEBOUNCED:

                    debounceLightSensor();

                    break;



                case MSG_UPDATE_BACKLIGHT_SETTINGS:

                    mAutoBrightnessSettingsChanged = true;

                    updateAutomaticBrightnessSettings();

                    updatePowerState();

                    break;

            }

        }

    }