Implement more granular locks for a Singleton scope in Guice.

Now when you can create two independent singletons using
the same injector in different threads.
This make it easy to create scopes creating singletons using
thread pools with all the concurrency being done by Guice.
As a nice side effect Singleton scope is no longer treated
specially in Guice codebase.

The obvious problem to solve is potential deadlocks:
A requires B, B requires C, C requires A where all are
singletons and all are created simultaneously.
It's impossible to detect this deadlock using information
within one thread, so we have to have a shared storage.

An idea is to have a map of creators' locks and a map
of which threads are waiting for other singletons to be created.
Using this information circular dependencies are trivially
discovered within O(N) where N is a number of concurrent threads.

Important to not that no other deadlock scenarios within
Guice code is introduced as Guice does not expose any
other scopes that can span several threads.

Now it would be possible for
client code to deadlock on itself with two lazy singletons
calling each other's providers during creation.
This is deemed as a non-issue as it is up to the client
to write a thread-safe code.
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=91610630

core/src/com/google/inject/internal/BindingProcessor.java

@@ -111,7 +111,7 @@ public Boolean visit(ProviderInstanceBinding<? extends T> binding) {
         // always visited with Binding<T>
         @SuppressWarnings("unchecked") 
         InternalFactory<T> factory = new InternalFactoryToInitializableAdapter<T>(
-            initializable, source, !injector.options.disableCircularProxies,
+            initializable, source,
             injector.provisionListenerStore.get((ProviderInstanceBinding<T>)binding));
         InternalFactory<? extends T> scopedFactory
             = Scoping.scope(key, injector, factory, source, scoping);
@@ -127,7 +127,7 @@ public Boolean visit(ProviderKeyBinding<? extends T> binding) {
         // always visited with Binding<T>
         @SuppressWarnings("unchecked") 
         BoundProviderFactory<T> boundProviderFactory = new BoundProviderFactory<T>(
-            injector, providerKey, source, !injector.options.disableCircularProxies,
+            injector, providerKey, source,
             injector.provisionListenerStore.get((ProviderKeyBinding<T>) binding));
         bindingData.addCreationListener(boundProviderFactory);
         InternalFactory<? extends T> scopedFactory = Scoping.scope(

core/src/com/google/inject/internal/BoundProviderFactory.java

@@ -38,9 +38,8 @@ final class BoundProviderFactory<T> extends ProviderInternalFactory<T> implement
       InjectorImpl injector,
       Key<? extends javax.inject.Provider<? extends T>> providerKey,
       Object source,
-      boolean allowProxy,
       ProvisionListenerStackCallback<T> provisionCallback) {
-    super(source, allowProxy);
+    super(source);
     this.provisionCallback = checkNotNull(provisionCallback, "provisionCallback");
     this.injector = injector;
     this.providerKey = providerKey;
@@ -60,7 +59,7 @@ public T get(Errors errors, InternalContext context, Dependency<?> dependency, b
     try {
       errors = errors.withSource(providerKey);
       javax.inject.Provider<? extends T> provider = providerFactory.get(errors, context, dependency, true);
-      return circularGet(provider, errors, context, dependency, linked, provisionCallback);
+      return circularGet(provider, errors, context, dependency, provisionCallback);
     } finally {
       context.popState();
     }

core/src/com/google/inject/internal/ConstructionContext.java

@@ -16,6 +16,8 @@
 
 package com.google.inject.internal;
 
+import com.google.inject.internal.InjectorImpl.InjectorOptions;
+
 import java.lang.reflect.Proxy;
 import java.util.ArrayList;
 import java.util.List;
@@ -57,11 +59,11 @@ public void finishConstruction() {
     invocationHandlers = null;
   }
 
-  public Object createProxy(Errors errors, Class<?> expectedType) throws ErrorsException {
-    // TODO: if I create a proxy which implements all the interfaces of
-    // the implementation type, I'll be able to get away with one proxy
-    // instance (as opposed to one per caller).
-
+  public Object createProxy(Errors errors, InjectorOptions injectorOptions,
+      Class<?> expectedType) throws ErrorsException {
+    if (injectorOptions.disableCircularProxies) {
+      throw errors.circularProxiesDisabled(expectedType).toException();
+    }
     if (!expectedType.isInterface()) {
       throw errors.cannotSatisfyCircularDependency(expectedType).toException();
     }
@@ -73,6 +75,9 @@ public Object createProxy(Errors errors, Class<?> expectedType) throws ErrorsExc
     DelegatingInvocationHandler<T> invocationHandler = new DelegatingInvocationHandler<T>();
     invocationHandlers.add(invocationHandler);
 
+    // TODO: if I create a proxy which implements all the interfaces of
+    // the implementation type, I'll be able to get away with one proxy
+    // instance (as opposed to one per caller).
     ClassLoader classLoader = BytecodeGen.getClassLoader(expectedType);
     return expectedType.cast(Proxy.newProxyInstance(classLoader,
         new Class[] { expectedType, CircularDependencyProxy.class }, invocationHandler));
@@ -83,6 +88,8 @@ public void setProxyDelegates(T delegate) {
       for (DelegatingInvocationHandler<T> handler : invocationHandlers) {
         handler.setDelegate(delegate);
       }
+      // initialization of each handler can happen no more than once
+      invocationHandlers = null;
     }
   }
 }

core/src/com/google/inject/internal/ConstructorBindingImpl.java

@@ -133,7 +133,6 @@ private static boolean hasAtInject(Constructor cxtor) {
 
   @SuppressWarnings("unchecked") // the result type always agrees with the ConstructorInjector type
   public void initialize(InjectorImpl injector, Errors errors) throws ErrorsException {
-    factory.allowCircularProxy = !injector.options.disableCircularProxies;
     factory.constructorInjector =
         (ConstructorInjector<T>) injector.constructors.get(constructorInjectionPoint, errors);
     factory.provisionCallback =
@@ -246,7 +245,6 @@ public int hashCode() {
   private static class Factory<T> implements InternalFactory<T> {
     private final boolean failIfNotLinked;
     private final Key<?> key;
-    private boolean allowCircularProxy;
     private ConstructorInjector<T> constructorInjector;
     private ProvisionListenerStackCallback<T> provisionCallback;
 
@@ -267,7 +265,7 @@ public T get(Errors errors, InternalContext context, Dependency<?> dependency, b
       // This may not actually be safe because it could return a super type of T (if that's all the
       // client needs), but it should be OK in practice thanks to the wonders of erasure.
       return (T) constructorInjector.construct(errors, context,
-          dependency.getKey().getTypeLiteral().getRawType(), allowCircularProxy, provisionCallback);
+          dependency.getKey().getTypeLiteral().getRawType(), provisionCallback);
     }
   }
 }

core/src/com/google/inject/internal/ConstructorInjector.java

@@ -59,19 +59,16 @@ ConstructionProxy<T> getConstructionProxy() {
    * it may return a proxy.
    */
   Object construct(final Errors errors, final InternalContext context,
-      Class<?> expectedType, boolean allowProxy,
+      Class<?> expectedType,
       ProvisionListenerStackCallback<T> provisionCallback)
       throws ErrorsException {
     final ConstructionContext<T> constructionContext = context.getConstructionContext(this);
 
     // We have a circular reference between constructors. Return a proxy.
     if (constructionContext.isConstructing()) {
-      if(!allowProxy) {
-        throw errors.circularProxiesDisabled(expectedType).toException();
-      } else {      
-        // TODO (crazybob): if we can't proxy this object, can we proxy the other object?
-        return constructionContext.createProxy(errors, expectedType);
-      }
+      // TODO (crazybob): if we can't proxy this object, can we proxy the other object?
+      return constructionContext.createProxy(
+          errors, context.getInjectorOptions(), expectedType);
     }
 
     // If we're re-entering this factory while injecting fields or methods,
@@ -85,7 +82,7 @@ Object construct(final Errors errors, final InternalContext context,
     try {
       // Optimization: Don't go through the callback stack if we have no listeners.
       if (!provisionCallback.hasListeners()) {
-        return provision(errors, context, constructionContext);        
+        return provision(errors, context, constructionContext);
       } else {
         return provisionCallback.provision(errors, context, new ProvisionCallback<T>() {
           public T call() throws ErrorsException {