Hold partial wakelock during shutdown to avoid entering sleep

The ShutdownThread can get suspended while in progress if the
device enters sleep by the user pressing the power-key, or if it is
started (in sleep) from the BatteryService upon a dead battery
notification. If the device is woken up before the battery is
drained, the ShutdownThread will resume and finally complete
the shutdown, but if not the phone will stay in sleep until the
battery level is so low that the power is ruthlessly cut.

Change-Id: If64429fd0c98a9136141942be6c337b5c79cf4f1

Author: Mattias Larsson

core/java/com/android/internal/app/ShutdownThread.java

@@ -67,7 +67,8 @@ public final class ShutdownThread extends Thread {
     private boolean mActionDone;
     private Context mContext;
     private PowerManager mPowerManager;
-    private PowerManager.WakeLock mWakeLock;
+    private PowerManager.WakeLock mCpuWakeLock;
+    private PowerManager.WakeLock mScreenWakeLock;
     private Handler mHandler;
 
     private ShutdownThread() {
@@ -155,20 +156,36 @@ private static void beginShutdownSequence(Context context) {
 
         pd.show();
 
-        // start the thread that initiates shutdown
         sInstance.mContext = context;
         sInstance.mPowerManager = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
-        sInstance.mWakeLock = null;
+
+        // make sure we never fall asleep again
+        sInstance.mCpuWakeLock = null;
+        try {
+            sInstance.mCpuWakeLock = sInstance.mPowerManager.newWakeLock(
+                    PowerManager.PARTIAL_WAKE_LOCK, TAG + "-cpu");
+            sInstance.mCpuWakeLock.setReferenceCounted(false);
+            sInstance.mCpuWakeLock.acquire();
+        } catch (SecurityException e) {
+            Log.w(TAG, "No permission to acquire wake lock", e);
+            sInstance.mCpuWakeLock = null;
+        }
+
+        // also make sure the screen stays on for better user experience
+        sInstance.mScreenWakeLock = null;
         if (sInstance.mPowerManager.isScreenOn()) {
             try {
-                sInstance.mWakeLock = sInstance.mPowerManager.newWakeLock(
-                        PowerManager.FULL_WAKE_LOCK, "Shutdown");
-                sInstance.mWakeLock.acquire();
+                sInstance.mScreenWakeLock = sInstance.mPowerManager.newWakeLock(
+                        PowerManager.FULL_WAKE_LOCK, TAG + "-screen");
+                sInstance.mScreenWakeLock.setReferenceCounted(false);
+                sInstance.mScreenWakeLock.acquire();
             } catch (SecurityException e) {
                 Log.w(TAG, "No permission to acquire wake lock", e);
-                sInstance.mWakeLock = null;
+                sInstance.mScreenWakeLock = null;
             }
         }
+
+        // start the thread that initiates shutdown
         sInstance.mHandler = new Handler() {
         };
         sInstance.start();