package org.opendaylight.mdsal.binding.dom.codec.impl;
import com.google.common.collect.Iterables;
-import org.checkerframework.checker.lock.qual.Holding;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
import org.eclipse.jdt.annotation.NonNull;
import org.opendaylight.mdsal.binding.dom.codec.api.BindingDataObjectCodecTreeNode.ChildAddressabilitySummary;
import org.opendaylight.mdsal.binding.dom.codec.impl.NodeCodecContext.CodecContextFactory;
import org.opendaylight.yangtools.yang.model.api.AugmentationSchemaNode;
import org.opendaylight.yangtools.yang.model.api.CaseSchemaNode;
import org.opendaylight.yangtools.yang.model.api.ChoiceSchemaNode;
+import org.opendaylight.yangtools.yang.model.api.ContainerLike;
import org.opendaylight.yangtools.yang.model.api.ContainerSchemaNode;
import org.opendaylight.yangtools.yang.model.api.DataNodeContainer;
import org.opendaylight.yangtools.yang.model.api.DataSchemaNode;
import org.opendaylight.yangtools.yang.model.api.DocumentedNode.WithStatus;
+import org.opendaylight.yangtools.yang.model.api.EffectiveModelContext;
import org.opendaylight.yangtools.yang.model.api.ListSchemaNode;
import org.opendaylight.yangtools.yang.model.api.NotificationDefinition;
import org.opendaylight.yangtools.yang.model.api.SchemaContext;
final class DataContainerCodecPrototype<T extends WithStatus> implements NodeContextSupplier {
private static final Logger LOG = LoggerFactory.getLogger(DataContainerCodecPrototype.class);
+ private static final VarHandle INSTANCE;
+
+ static {
+ try {
+ INSTANCE = MethodHandles.lookup().findVarHandle(DataContainerCodecPrototype.class,
+ "instance", DataContainerCodecContext.class);
+ } catch (NoSuchFieldException | IllegalAccessException e) {
+ throw new ExceptionInInitializerError(e);
+ }
+ }
+
private final T schema;
private final QNameModule namespace;
private final CodecContextFactory factory;
private final PathArgument yangArg;
private final ChildAddressabilitySummary childAddressabilitySummary;
- /*
- * FIXME: This field is now utterly in the hot path of CodecDataObject's instantiation of data. It is volatile
- * support double-checked locking, as detailed in
- * https://en.wikipedia.org/wiki/Double-checked_locking#Usage_in_Java.
- *
- * Removing volatile here would seem to be worthwhile, as it would mean that in the initialized case we end
- * up with no happens-before synchronization between threads, allowing JIT to perform better.
- *
- * Since we are on Java 5+, DataContainerCodecContext and its subclasses play a role here. All of their
- * fields are either final or volatile, so intuition would indicate they themselves could (already?) be
- * acting in the same capacity as "FinalWrapper" in the above example does -- in which case we can safely
- * remove the volatile access altogether, after documenting this fact there (and potentially placing some
- * guards).
- *
- * The presence of volatile fields seems to violate this, as
- * http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html mentions "such that all of the
- * fields of Helper are final".
- *
- * There are only two violations, both relating to dynamic discovery of augmentations, which should be
- * eliminated once we have constant class loader visibility (and thus can discover all valid augmentations
- * and aliases). Alternatively, adding an indirection could be considered after the effects are fully
- * understood.
- *
- * Alternatively we can consider the use of VarHandle acquire/release mechanics to remove this instance
- * from global synchronization order -- that would be a Java 9+ concern, though.
- *
- * Finally, the benefits of addressing this are masked by CodecDataObject operating on volatiles, hence
- * already doing a barrier very close to us -- thus reducing the scope in which code can be reordered.
- * If CodecDataObject moves to VarHandles and uses acquire/release there, we will be put on the spot here,
- * though.
- */
+ // Accessed via INSTANCE
+ @SuppressWarnings("unused")
private volatile DataContainerCodecContext<?, T> instance;
@SuppressWarnings("unchecked")
} else if (nodeSchema instanceof ChoiceSchemaNode) {
boolean haveAddressable = false;
boolean haveUnaddressable = false;
- for (CaseSchemaNode child : ((ChoiceSchemaNode) nodeSchema).getCases().values()) {
+ for (CaseSchemaNode child : ((ChoiceSchemaNode) nodeSchema).getCases()) {
switch (computeChildAddressabilitySummary(child)) {
case ADDRESSABLE:
haveAddressable = true;
return ChildAddressabilitySummary.UNADDRESSABLE;
}
- static DataContainerCodecPrototype<SchemaContext> rootPrototype(final CodecContextFactory factory) {
- final SchemaContext schema = factory.getRuntimeContext().getSchemaContext();
- final NodeIdentifier arg = NodeIdentifier.create(schema.getQName());
+ static DataContainerCodecPrototype<EffectiveModelContext> rootPrototype(final CodecContextFactory factory) {
+ final EffectiveModelContext schema = factory.getRuntimeContext().getEffectiveModelContext();
+ final NodeIdentifier arg = NodeIdentifier.create(SchemaContext.NAME);
return new DataContainerCodecPrototype<>(DataRoot.class, arg, schema, factory);
}
- @SuppressWarnings({ "unchecked", "rawtypes" })
static <T extends DataSchemaNode> DataContainerCodecPrototype<T> from(final Class<?> cls, final T schema,
final CodecContextFactory factory) {
- return new DataContainerCodecPrototype(cls, NodeIdentifier.create(schema.getQName()), schema, factory);
+ return new DataContainerCodecPrototype<>(cls, NodeIdentifier.create(schema.getQName()), schema, factory);
}
- @SuppressWarnings({ "unchecked", "rawtypes" })
static <T extends DataSchemaNode> DataContainerCodecPrototype<T> from(final Item<?> bindingArg, final T schema,
final CodecContextFactory factory) {
- return new DataContainerCodecPrototype(bindingArg, NodeIdentifier.create(schema.getQName()), schema, factory);
+ return new DataContainerCodecPrototype<>(bindingArg, NodeIdentifier.create(schema.getQName()), schema, factory);
}
- @SuppressWarnings({ "rawtypes", "unchecked" })
- static DataContainerCodecPrototype<?> from(final Class<?> augClass, final AugmentationIdentifier arg,
- final AugmentationSchemaNode schema, final CodecContextFactory factory) {
- return new DataContainerCodecPrototype(augClass, arg, schema, factory);
+ static DataContainerCodecPrototype<AugmentationSchemaNode> from(final Class<?> augClass,
+ final AugmentationIdentifier arg, final AugmentationSchemaNode schema, final CodecContextFactory factory) {
+ return new DataContainerCodecPrototype<>(augClass, arg, schema, factory);
}
static DataContainerCodecPrototype<NotificationDefinition> from(final Class<?> augClass,
return new DataContainerCodecPrototype<>(augClass,arg, schema, factory);
}
- protected T getSchema() {
+ T getSchema() {
return schema;
}
return childAddressabilitySummary;
}
- protected QNameModule getNamespace() {
+ QNameModule getNamespace() {
return namespace;
}
- protected CodecContextFactory getFactory() {
+ CodecContextFactory getFactory() {
return factory;
}
- protected Class<?> getBindingClass() {
+ Class<?> getBindingClass() {
return bindingArg.getType();
}
- protected Item<?> getBindingArg() {
+ Item<?> getBindingArg() {
return bindingArg;
}
- protected PathArgument getYangArg() {
+ PathArgument getYangArg() {
return yangArg;
}
@Override
public DataContainerCodecContext<?, T> get() {
- DataContainerCodecContext<?, T> tmp = instance;
- if (tmp == null) {
- synchronized (this) {
- tmp = instance;
- if (tmp == null) {
- instance = tmp = createInstance();
- }
- }
- }
+ final DataContainerCodecContext<?, T> existing = (DataContainerCodecContext<?, T>) INSTANCE.getAcquire(this);
+ return existing != null ? existing : loadInstance();
+ }
- return tmp;
+ private @NonNull DataContainerCodecContext<?, T> loadInstance() {
+ final var tmp = createInstance();
+ final var witness = (DataContainerCodecContext<?, T>) INSTANCE.compareAndExchangeRelease(this, null, tmp);
+ return witness == null ? tmp : witness;
}
- @Holding("this")
@SuppressWarnings({ "rawtypes", "unchecked" })
+ // This method must allow concurrent loading, i.e. nothing in it may have effects outside of the loaded object
private @NonNull DataContainerCodecContext<?, T> createInstance() {
// FIXME: make protected abstract
- if (schema instanceof ContainerSchemaNode) {
+ if (schema instanceof ContainerLike) {
return new ContainerNodeCodecContext(this);
} else if (schema instanceof ListSchemaNode) {
return Identifiable.class.isAssignableFrom(getBindingClass())
throw new IllegalArgumentException("Unsupported type " + getBindingClass() + " " + schema);
}
+ // FIXME: eliminate with above createInstance() item
boolean isChoice() {
return schema instanceof ChoiceSchemaNode;
}
Code Review / mdsal.git / blobdiff