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Commit 235aab5b authored by Daniel's avatar Daniel Committed by Alex Salo
Browse files

Fix race condition of lazy service binding 

There is a race condition introduced by service binding and api calls,
checkAttention and onStartProximityUpdates. Fixing the race condition by
introducing a CountDownLatch that gets counted down on service binding
and reinitialized on service unbinding.

Bug: 219525510
Test: atest CtsAttentionServiceDeviceTestCases
Commented out and tested individual test at a time. Previous tests that
failed individually such as CheckAttentionSuccess or
ProximityUpdatesSuccess pass.

Change-Id: I168b325c65e8d82767f278c65d62268afa4060a1
(cherry picked from commit f6d7d7a7)
parent 5bb3da07

services/core/java/com/android/server/attention/AttentionManagerService.java

+26 −3
Original line number Diff line number Diff line
@@ -74,6 +74,8 @@ import java.io.FileDescriptor; 
import java.io.PrintWriter;

import java.util.Objects;

import java.util.Set;

import java.util.concurrent.CountDownLatch;

import java.util.concurrent.TimeUnit;



/**

 * An attention service implementation that runs in System Server process.
@@ -87,6 +89,9 @@ public class AttentionManagerService extends SystemService { 
    /** Service will unbind if connection is not used for that amount of time. */

    private static final long CONNECTION_TTL_MILLIS = 60_000;



    /** How long AttentionManagerService will wait for service binding after lazy binding. */

    private static final long SERVICE_BINDING_WAIT_MILLIS = 1000;



    /** DeviceConfig flag name, if {@code true}, enables AttentionManagerService features. */

    @VisibleForTesting

    static final String KEY_SERVICE_ENABLED = "service_enabled";
@@ -129,6 +134,7 @@ public class AttentionManagerService extends SystemService { 
    @GuardedBy("mLock")

    private boolean mBinding;

    private AttentionHandler mAttentionHandler;

    private CountDownLatch mServiceBindingLatch;



    @VisibleForTesting

    ComponentName mComponentName;
@@ -161,6 +167,7 @@ public class AttentionManagerService extends SystemService { 
        mLock = lock;

        mAttentionHandler = handler;

        mPrivacyManager = SensorPrivacyManager.getInstance(context);

        mServiceBindingLatch = new CountDownLatch(1);

    }



    @Override
@@ -275,13 +282,16 @@ public class AttentionManagerService extends SystemService { 
        }



        synchronized (mLock) {

            final long now = SystemClock.uptimeMillis();

            // schedule shutting down the connection if no one resets this timer

            freeIfInactiveLocked();



            // lazily start the service, which should be very lightweight to start

            bindLocked();



        }

        final long now = SystemClock.uptimeMillis();

        // Proceed when the service binding is complete.

        awaitServiceBinding(Math.min(SERVICE_BINDING_WAIT_MILLIS, timeout));

        synchronized (mLock) {

            // throttle frequent requests

            final AttentionCheckCache cache = mAttentionCheckCacheBuffer == null ? null

                    : mAttentionCheckCacheBuffer.getLast();
@@ -361,7 +371,10 @@ public class AttentionManagerService extends SystemService { 


            // lazily start the service, which should be very lightweight to start

            bindLocked();



        }

        // Proceed when the service binding is complete.

        awaitServiceBinding(SERVICE_BINDING_WAIT_MILLIS);

        synchronized (mLock) {

            /*

            Prevent spamming with multiple requests, only one at a time is allowed.

            If there are use-cases for keeping track of multiple requests, we
@@ -419,6 +432,14 @@ public class AttentionManagerService extends SystemService { 
        return context.getPackageManager().getAttentionServicePackageName();

    }



    private void awaitServiceBinding(long millis) {

        try {

            mServiceBindingLatch.await(millis, TimeUnit.MILLISECONDS);

        } catch (InterruptedException e) {

            Slog.e(LOG_TAG, "Interrupted while waiting to bind Attention Service.", e);

        }

    }



    /**

     * Provides attention service component name at runtime, making sure it's provided by the

     * system.
@@ -711,6 +732,7 @@ public class AttentionManagerService extends SystemService { 
        @Override

        public void onServiceConnected(ComponentName name, IBinder service) {

            init(IAttentionService.Stub.asInterface(service));

            mServiceBindingLatch.countDown();

        }



        @Override
@@ -730,6 +752,7 @@ public class AttentionManagerService extends SystemService { 


        void cleanupService() {

            init(null);

            mServiceBindingLatch = new CountDownLatch(1);

        }



        private void init(@Nullable IAttentionService service) {