Revise singleton registry for lenient locking (fallback instead of de…

…adlock)

Closes gh-23501

spring-aop/src/main/java/org/springframework/aop/aspectj/annotation/BeanFactoryAspectInstanceFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -109,13 +109,8 @@ public Object getAspectCreationMutex() {
 			// Rely on singleton semantics provided by the factory -> no local lock.
 			return null;
 		}
-		else if (this.beanFactory instanceof ConfigurableBeanFactory cbf) {
-			// No singleton guarantees from the factory -> let's lock locally but
-			// reuse the factory's singleton lock, just in case a lazy dependency
-			// of our advice bean happens to trigger the singleton lock implicitly...
-			return cbf.getSingletonMutex();
-		}
 		else {
+			// No singleton guarantees from the factory -> let's lock locally.
 			return this;
 		}
 	}

spring-aop/src/main/java/org/springframework/aop/support/AbstractBeanFactoryPointcutAdvisor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,7 +23,6 @@
 
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
-import org.springframework.beans.factory.config.ConfigurableBeanFactory;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -52,7 +51,7 @@ public abstract class AbstractBeanFactoryPointcutAdvisor extends AbstractPointcu
 	@Nullable
 	private transient volatile Advice advice;
 
-	private transient volatile Object adviceMonitor = new Object();
+	private transient Object adviceMonitor = new Object();
 
 
 	/**
@@ -78,16 +77,6 @@ public String getAdviceBeanName() {
 	@Override
 	public void setBeanFactory(BeanFactory beanFactory) {
 		this.beanFactory = beanFactory;
-		resetAdviceMonitor();
-	}
-
-	private void resetAdviceMonitor() {
-		if (this.beanFactory instanceof ConfigurableBeanFactory cbf) {
-			this.adviceMonitor = cbf.getSingletonMutex();
-		}
-		else {
-			this.adviceMonitor = new Object();
-		}
 	}
 
 	/**
@@ -118,9 +107,7 @@ public Advice getAdvice() {
 			return advice;
 		}
 		else {
-			// No singleton guarantees from the factory -> let's lock locally but
-			// reuse the factory's singleton lock, just in case a lazy dependency
-			// of our advice bean happens to trigger the singleton lock implicitly...
+			// No singleton guarantees from the factory -> let's lock locally.
 			synchronized (this.adviceMonitor) {
 				advice = this.advice;
 				if (advice == null) {
@@ -155,7 +142,7 @@ private void readObject(ObjectInputStream ois) throws IOException, ClassNotFound
 		ois.defaultReadObject();
 
 		// Initialize transient fields.
-		resetAdviceMonitor();
+		this.adviceMonitor = new Object();
 	}
 
 }

spring-beans/src/main/java/org/springframework/beans/factory/config/SingletonBeanRegistry.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -129,7 +129,10 @@ public interface SingletonBeanRegistry {
 	 * Return the singleton mutex used by this registry (for external collaborators).
 	 * @return the mutex object (never {@code null})
 	 * @since 4.2
+	 * @deprecated as of 6.2, in favor of lenient singleton locking
+	 * (with this method returning an arbitrary object to lock on)
 	 */
+	@Deprecated(since = "6.2")
 	Object getSingletonMutex();
 
 }

spring-beans/src/main/java/org/springframework/beans/factory/support/AbstractAutowireCapableBeanFactory.java

@@ -972,59 +972,54 @@ protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd,
 	 */
 	@Nullable
 	private FactoryBean<?> getSingletonFactoryBeanForTypeCheck(String beanName, RootBeanDefinition mbd) {
-		synchronized (getSingletonMutex()) {
-			BeanWrapper bw = this.factoryBeanInstanceCache.get(beanName);
-			if (bw != null) {
-				return (FactoryBean<?>) bw.getWrappedInstance();
-			}
-			Object beanInstance = getSingleton(beanName, false);
-			if (beanInstance instanceof FactoryBean<?> factoryBean) {
-				return factoryBean;
-			}
-			if (isSingletonCurrentlyInCreation(beanName) ||
-					(mbd.getFactoryBeanName() != null && isSingletonCurrentlyInCreation(mbd.getFactoryBeanName()))) {
-				return null;
-			}
+		BeanWrapper bw = this.factoryBeanInstanceCache.get(beanName);
+		if (bw != null) {
+			return (FactoryBean<?>) bw.getWrappedInstance();
+		}
+		Object beanInstance = getSingleton(beanName, false);
+		if (beanInstance instanceof FactoryBean<?> factoryBean) {
+			return factoryBean;
+		}
+		if (isSingletonCurrentlyInCreation(beanName) ||
+				(mbd.getFactoryBeanName() != null && isSingletonCurrentlyInCreation(mbd.getFactoryBeanName()))) {
+			return null;
+		}
 
-			Object instance;
-			try {
-				// Mark this bean as currently in creation, even if just partially.
-				beforeSingletonCreation(beanName);
-				// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
-				instance = resolveBeforeInstantiation(beanName, mbd);
-				if (instance == null) {
-					bw = createBeanInstance(beanName, mbd, null);
-					instance = bw.getWrappedInstance();
-				}
+		Object instance;
+		try {
+			// Mark this bean as currently in creation, even if just partially.
+			beforeSingletonCreation(beanName);
+			// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
+			instance = resolveBeforeInstantiation(beanName, mbd);
+			if (instance == null) {
+				bw = createBeanInstance(beanName, mbd, null);
+				instance = bw.getWrappedInstance();
+				this.factoryBeanInstanceCache.put(beanName, bw);
 			}
-			catch (UnsatisfiedDependencyException ex) {
-				// Don't swallow, probably misconfiguration...
+		}
+		catch (UnsatisfiedDependencyException ex) {
+			// Don't swallow, probably misconfiguration...
+			throw ex;
+		}
+		catch (BeanCreationException ex) {
+			// Don't swallow a linkage error since it contains a full stacktrace on
+			// first occurrence... and just a plain NoClassDefFoundError afterwards.
+			if (ex.contains(LinkageError.class)) {
 				throw ex;
 			}
-			catch (BeanCreationException ex) {
-				// Don't swallow a linkage error since it contains a full stacktrace on
-				// first occurrence... and just a plain NoClassDefFoundError afterwards.
-				if (ex.contains(LinkageError.class)) {
-					throw ex;
-				}
-				// Instantiation failure, maybe too early...
-				if (logger.isDebugEnabled()) {
-					logger.debug("Bean creation exception on singleton FactoryBean type check: " + ex);
-				}
-				onSuppressedException(ex);
-				return null;
-			}
-			finally {
-				// Finished partial creation of this bean.
-				afterSingletonCreation(beanName);
-			}
-
-			FactoryBean<?> fb = getFactoryBean(beanName, instance);
-			if (bw != null) {
-				this.factoryBeanInstanceCache.put(beanName, bw);
+			// Instantiation failure, maybe too early...
+			if (logger.isDebugEnabled()) {
+				logger.debug("Bean creation exception on singleton FactoryBean type check: " + ex);
 			}
-			return fb;
+			onSuppressedException(ex);
+			return null;
+		}
+		finally {
+			// Finished partial creation of this bean.
+			afterSingletonCreation(beanName);
 		}
+
+		return getFactoryBean(beanName, instance);
 	}
 
 	/**
@@ -1912,21 +1907,17 @@ protected Object postProcessObjectFromFactoryBean(Object object, String beanName
 	 */
 	@Override
 	protected void removeSingleton(String beanName) {
-		synchronized (getSingletonMutex()) {
-			super.removeSingleton(beanName);
-			this.factoryBeanInstanceCache.remove(beanName);
-		}
+		super.removeSingleton(beanName);
+		this.factoryBeanInstanceCache.remove(beanName);
 	}
 
 	/**
 	 * Overridden to clear FactoryBean instance cache as well.
 	 */
 	@Override
 	protected void clearSingletonCache() {
-		synchronized (getSingletonMutex()) {
-			super.clearSingletonCache();
-			this.factoryBeanInstanceCache.clear();
-		}
+		super.clearSingletonCache();
+		this.factoryBeanInstanceCache.clear();
 	}
 
 	/**