Merge "Avoid service wrapper initialization deadlock." into pi-dev (1e36211a) · Commits · e / os / android_frameworks_base

core/java/android/app/ContextImpl.java

+12 −0

Original line number	Diff line number	Diff line
		@@ -92,6 +92,7 @@ import java.nio.ByteOrder;
		import java.util.ArrayList;
		import java.util.Objects;
		import java.util.concurrent.Executor;
		import java.util.concurrent.atomic.AtomicInteger;

		class ReceiverRestrictedContext extends ContextWrapper {
		ReceiverRestrictedContext(Context base) {
		@@ -208,6 +209,17 @@ class ContextImpl extends Context {
		// The system service cache for the system services that are cached per-ContextImpl.
		final Object[] mServiceCache = SystemServiceRegistry.createServiceCache();

		static final int STATE_UNINITIALIZED = 0;
		static final int STATE_INITIALIZING = 1;
		static final int STATE_READY = 2;

		/**
		* Initialization state for each service. Any of {@link #STATE_UNINITIALIZED},
		* {@link #STATE_INITIALIZING} or {@link #STATE_READY},
		*/
		final AtomicInteger[] mServiceInitializationStateArray =
		SystemServiceRegistry.createServiceInitializationStateArray();

		static ContextImpl getImpl(Context context) {
		Context nextContext;
		while ((context instanceof ContextWrapper) &&

core/java/android/app/SystemServiceRegistry.java

+86 −5

Original line number	Diff line number	Diff line
		@@ -160,6 +160,7 @@ import com.android.internal.os.IDropBoxManagerService;
		import com.android.internal.policy.PhoneLayoutInflater;

		import java.util.HashMap;
		import java.util.concurrent.atomic.AtomicInteger;

		/**
		* Manages all of the system services that can be returned by {@link Context#getSystemService}.
		@@ -992,6 +993,10 @@ final class SystemServiceRegistry {
		return new Object[sServiceCacheSize];
		}

		public static AtomicInteger[] createServiceInitializationStateArray() {
		return new AtomicInteger[sServiceCacheSize];
		}

		/**
		* Gets a system service from a given context.
		*/
		@@ -1040,19 +1045,95 @@ final class SystemServiceRegistry {
		@SuppressWarnings("unchecked")
		public final T getService(ContextImpl ctx) {
		final Object[] cache = ctx.mServiceCache;
		synchronized (cache) {
		// Fetch or create the service.

		// Fast path. If it's already cached, just return it.
		Object service = cache[mCacheIndex];
		if (service == null) {
		if (service != null) {
		return (T) service;
		}

		// Slow path.
		final AtomicInteger[] gates = ctx.mServiceInitializationStateArray;
		final AtomicInteger gate;

		synchronized (cache) {
		// See if it's cached or not again, with the lock held this time.
		service = cache[mCacheIndex];
		if (service != null) {
		return (T) service;
		}

		// Not initialized yet. Create an atomic boolean to control which thread should
		// instantiate the service.
		if (gates[mCacheIndex] != null) {
		gate = gates[mCacheIndex];
		} else {
		gate = new AtomicInteger(ContextImpl.STATE_UNINITIALIZED);
		gates[mCacheIndex] = gate;
		}
		}

		// Not cached yet.
		//
		// Note multiple threads can reach here for the same service on the same context
		// concurrently.
		//
		// Now we're going to instantiate the service, but do so without the cache held;
		// otherwise it could deadlock. (b/71882178)
		//
		// However we still don't want to instantiate the same service multiple times, so
		// use the atomic integer to ensure only one thread will call createService().

		if (gate.compareAndSet(
		ContextImpl.STATE_UNINITIALIZED, ContextImpl.STATE_INITIALIZING)) {
		try {
		// This thread is the first one to get here. Instantiate the service
		// without the cache lock held.
		try {
		service = createService(ctx);

		synchronized (cache) {
		cache[mCacheIndex] = service;
		}
		} catch (ServiceNotFoundException e) {
		onServiceNotFound(e);
		}
		} finally {
		// Tell the all other threads that the cache is ready now.
		// (But it's still be null in case of ServiceNotFoundException.)
		synchronized (gate) {
		gate.set(ContextImpl.STATE_READY);
		gate.notifyAll();
		}
		}
		return (T) service;
		}
		// Other threads will wait on the gate lock.
		synchronized (gate) {
		boolean interrupted = false;

		// Note: We check whether "state == STATE_READY", not
		// "cache[mCacheIndex] != null", because "cache[mCacheIndex] == null"
		// is still a valid outcome in the ServiceNotFoundException case.
		while (gate.get() != ContextImpl.STATE_READY) {
		try {
		gate.wait();
		} catch (InterruptedException e) {
		Log.w(TAG, "getService() interrupted");
		interrupted = true;
		}
		}
		if (interrupted) {
		Thread.currentThread().interrupt();
		}
		}
		// Now the first thread has initialized it.
		// It may still be null if ServiceNotFoundException was thrown, but that shouldn't
		// happen, so we'll just return null here in that case.
		synchronized (cache) {
		service = cache[mCacheIndex];
		}
		return (T) service;
		}

		public abstract T createService(ContextImpl ctx) throws ServiceNotFoundException;