Acquire the backup wakelock with a timeout

There have been a few reports of the backup service failing to call
release() on the wakelock and draining battery for hours. These are rare
failures and hard to debug individually but with the timeout we will
limit the worst case significantly.

I am setting the default timeout to 30 minutes. This should be more than
enough time for a backup or restore operation. If in the future these
operation get longer, the timeout is configurable by a setting.

Test: atest CtsBackupTestCases
Fixes: 364931501
Fixes: 357769443
Fixes: 289789401
Flag: EXEMPT bugfix
Change-Id: Iaac0218d5258031b6f67c3c56c776ce098e8a8c4

2 files changed, 24 insertions, 7 deletions

diff --git a/services/backup/java/com/android/server/backup/BackupManagerConstants.java b/services/backup/java/com/android/server/backup/BackupManagerConstants.java
index 4bd987a17447..b753d01562ca 100644
--- a/services/backup/java/com/android/server/backup/BackupManagerConstants.java
+++ b/services/backup/java/com/android/server/backup/BackupManagerConstants.java
@@ -72,6 +72,9 @@ public class BackupManagerConstants extends KeyValueSettingObserver {
     public static final String BACKUP_FINISHED_NOTIFICATION_RECEIVERS =
             "backup_finished_notification_receivers";
 
+    @VisibleForTesting
+    public static final String WAKELOCK_TIMEOUT_MILLIS = "wakelock_timeout_millis";
+
     // Hard coded default values.
     @VisibleForTesting
     public static final long DEFAULT_KEY_VALUE_BACKUP_INTERVAL_MILLISECONDS =
@@ -97,6 +100,9 @@ public class BackupManagerConstants extends KeyValueSettingObserver {
     @VisibleForTesting
     public static final String DEFAULT_BACKUP_FINISHED_NOTIFICATION_RECEIVERS = "";
 
+    @VisibleForTesting
+    public static final long DEFAULT_WAKELOCK_TIMEOUT_MILLIS = 30 * 60 * 1000; // 30 minutes
+
     // Backup manager constants.
     private long mKeyValueBackupIntervalMilliseconds;
     private long mKeyValueBackupFuzzMilliseconds;
@@ -106,6 +112,7 @@ public class BackupManagerConstants extends KeyValueSettingObserver {
     private boolean mFullBackupRequireCharging;
     private int mFullBackupRequiredNetworkType;
     private String[] mBackupFinishedNotificationReceivers;
+    private long mWakelockTimeoutMillis;
 
     public BackupManagerConstants(Handler handler, ContentResolver resolver) {
         super(handler, resolver, Settings.Secure.getUriFor(SETTING));
@@ -152,6 +159,8 @@ public class BackupManagerConstants extends KeyValueSettingObserver {
         } else {
             mBackupFinishedNotificationReceivers = backupFinishedNotificationReceivers.split(":");
         }
+        mWakelockTimeoutMillis = parser.getLong(WAKELOCK_TIMEOUT_MILLIS,
+                DEFAULT_WAKELOCK_TIMEOUT_MILLIS);
     }
 
     // The following are access methods for the individual parameters.
@@ -235,4 +244,9 @@ public class BackupManagerConstants extends KeyValueSettingObserver {
         }
         return mBackupFinishedNotificationReceivers;
     }
+
+    public synchronized long getWakelockTimeoutMillis() {
+        Slog.v(TAG, "wakelock timeout: " + mWakelockTimeoutMillis);
+        return mWakelockTimeoutMillis;
+    }
 }
diff --git a/services/backup/java/com/android/server/backup/UserBackupManagerService.java b/services/backup/java/com/android/server/backup/UserBackupManagerService.java
index 549f8fa77b53..ac1f50f85d64 100644
--- a/services/backup/java/com/android/server/backup/UserBackupManagerService.java
+++ b/services/backup/java/com/android/server/backup/UserBackupManagerService.java
@@ -181,11 +181,14 @@ public class UserBackupManagerService {
     public static class BackupWakeLock {
         private final PowerManager.WakeLock mPowerManagerWakeLock;
         private boolean mHasQuit = false;
-        private int mUserId;
+        private final int mUserId;
+        private final BackupManagerConstants mBackupManagerConstants;
 
-        public BackupWakeLock(PowerManager.WakeLock powerManagerWakeLock, int userId) {
+        public BackupWakeLock(PowerManager.WakeLock powerManagerWakeLock, int userId,
+                BackupManagerConstants backupManagerConstants) {
             mPowerManagerWakeLock = powerManagerWakeLock;
             mUserId = userId;
+            mBackupManagerConstants = backupManagerConstants;
         }
 
         /** Acquires the {@link PowerManager.WakeLock} if hasn't been quit. */
@@ -199,7 +202,9 @@ public class UserBackupManagerService {
                                         + mPowerManagerWakeLock.getTag()));
                 return;
             }
-            mPowerManagerWakeLock.acquire();
+            // Set a timeout for the wakelock. Otherwise if we fail internally and never call
+            // release(), the device might stay awake and drain battery indefinitely.
+            mPowerManagerWakeLock.acquire(mBackupManagerConstants.getWakelockTimeoutMillis());
             Slog.v(
                     TAG,
                     addUserIdToLogMessage(
@@ -674,10 +679,8 @@ public class UserBackupManagerService {
         mBackupPreferences = new UserBackupPreferences(mContext, mBaseStateDir);
 
         // Power management
-        mWakelock = new BackupWakeLock(
-                mPowerManager.newWakeLock(
-                        PowerManager.PARTIAL_WAKE_LOCK,
-                        "*backup*-" + userId + "-" + userBackupThread.getThreadId()), userId);
+        mWakelock = new BackupWakeLock(mPowerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
+                "*backup*-" + userId + "-" + userBackupThread.getThreadId()), userId, mConstants);
 
         // Set up the various sorts of package tracking we do
         mFullBackupScheduleFile = new File(mBaseStateDir, "fb-schedule");