Merge "Simplify service wrapper initialization + make robust" into pi-dev (7c878a75) · Commits · e / os / android_frameworks_base

core/java/android/app/ContextImpl.java

+16 −3

Original line number	Diff line number	Diff line
		@@ -16,6 +16,7 @@

		package android.app;

		import android.annotation.IntDef;
		import android.annotation.NonNull;
		import android.annotation.Nullable;
		import android.annotation.TestApi;
		@@ -88,11 +89,12 @@ import java.io.FileOutputStream;
		import java.io.FilenameFilter;
		import java.io.IOException;
		import java.io.InputStream;
		import java.lang.annotation.Retention;
		import java.lang.annotation.RetentionPolicy;
		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) {
		@@ -212,13 +214,24 @@ class ContextImpl extends Context {
		static final int STATE_UNINITIALIZED = 0;
		static final int STATE_INITIALIZING = 1;
		static final int STATE_READY = 2;
		static final int STATE_NOT_FOUND = 3;

		/** @hide */
		@IntDef(prefix = { "STATE_" }, value = {
		STATE_UNINITIALIZED,
		STATE_INITIALIZING,
		STATE_READY,
		STATE_NOT_FOUND,
		})
		@Retention(RetentionPolicy.SOURCE)
		@interface ServiceInitializationState {}

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

		static ContextImpl getImpl(Context context) {
		Context nextContext;

core/java/android/app/SystemServiceRegistry.java

+55 −78

Original line number	Diff line number	Diff line
		@@ -18,6 +18,7 @@ package android.app;

		import android.accounts.AccountManager;
		import android.accounts.IAccountManager;
		import android.app.ContextImpl.ServiceInitializationState;
		import android.app.admin.DevicePolicyManager;
		import android.app.admin.IDevicePolicyManager;
		import android.app.job.IJobScheduler;
		@@ -160,7 +161,6 @@ 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}.
		@@ -993,10 +993,6 @@ final class SystemServiceRegistry {
		return new Object[sServiceCacheSize];
		}

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

		/**
		* Gets a system service from a given context.
		*/
		@@ -1037,7 +1033,10 @@ final class SystemServiceRegistry {
		static abstract class CachedServiceFetcher<T> implements ServiceFetcher<T> {
		private final int mCacheIndex;

		public CachedServiceFetcher() {
		CachedServiceFetcher() {
		// Note this class must be instantiated only by the static initializer of the
		// outer class (SystemServiceRegistry), which already does the synchronization,
		// so bare access to sServiceCacheSize is okay here.
		mCacheIndex = sServiceCacheSize++;
		}

		@@ -1045,95 +1044,73 @@ final class SystemServiceRegistry {
		@SuppressWarnings("unchecked")
		public final T getService(ContextImpl ctx) {
		final Object[] cache = ctx.mServiceCache;
		final int[] gates = ctx.mServiceInitializationStateArray;

		// Fast path. If it's already cached, just return it.
		Object service = cache[mCacheIndex];
		if (service != null) {
		return (T) service;
		for (;;) {
		boolean doInitialize = false;
		synchronized (cache) {
		// Return it if we already have a cached instance.
		T service = (T) cache[mCacheIndex];
		if (service != null \|\| gates[mCacheIndex] == ContextImpl.STATE_NOT_FOUND) {
		return service;
		}

		// Slow path.
		final AtomicInteger[] gates = ctx.mServiceInitializationStateArray;
		final AtomicInteger gate;
		// If we get here, there's no cached instance.

		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;
		// Grr... if gate is STATE_READY, then this means we initialized the service
		// once but someone cleared it.
		// We start over from STATE_UNINITIALIZED.
		if (gates[mCacheIndex] == ContextImpl.STATE_READY) {
		gates[mCacheIndex] = ContextImpl.STATE_UNINITIALIZED;
		}

		// 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;
		// It's possible for multiple threads to get here at the same time, so
		// use the "gate" to make sure only the first thread will call createService().

		// At this point, the gate must be either UNINITIALIZED or INITIALIZING.
		if (gates[mCacheIndex] == ContextImpl.STATE_UNINITIALIZED) {
		doInitialize = true;
		gates[mCacheIndex] = ContextImpl.STATE_INITIALIZING;
		}
		}

		// 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)) {
		if (doInitialize) {
		// Only the first thread gets here.

		T service = null;
		@ServiceInitializationState int newState = ContextImpl.STATE_NOT_FOUND;
		try {
		// This thread is the first one to get here. Instantiate the service
		// without the cache lock held.
		try {
		service = createService(ctx);
		newState = ContextImpl.STATE_READY;

		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();
		synchronized (cache) {
		cache[mCacheIndex] = service;
		gates[mCacheIndex] = newState;
		cache.notifyAll();
		}
		}
		return (T) service;
		return 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) {
		// The other threads will wait for the first thread to call notifyAll(),
		// and go back to the top and retry.
		synchronized (cache) {
		while (gates[mCacheIndex] < ContextImpl.STATE_READY) {
		try {
		gate.wait();
		cache.wait();
		} catch (InterruptedException e) {
		Log.w(TAG, "getService() interrupted");
		interrupted = true;
		}
		}
		if (interrupted) {
		Thread.currentThread().interrupt();
		return null;
		}
		}
		}
		// 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;