Thread Pinning occurs with VirtualThreads enabled (spring boot 3)

[keydon]

Describe the bug

when running a simple spring boot 3 with spring-amqp app with the debug-flag -Djdk.tracePinnedThreads=full Thread-Pinning occurs.

Thread[#60,ForkJoinPool-1-worker-9,5,CarrierThreads]
    java.base/java.lang.VirtualThread$VThreadContinuation.onPinned(Unknown Source)
    java.base/jdk.internal.vm.Continuation.onPinned0(Unknown Source)
    java.base/java.lang.VirtualThread.park(Unknown Source)
    java.base/java.lang.System$2.parkVirtualThread(Unknown Source)
    java.base/jdk.internal.misc.VirtualThreads.park(Unknown Source)
    java.base/java.util.concurrent.locks.LockSupport.park(Unknown Source)
    java.base/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(Unknown Source)
    java.base/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(Unknown Source)
    java.base/java.util.concurrent.locks.ReentrantLock$Sync.lock(Unknown Source)
    java.base/java.util.concurrent.locks.ReentrantLock.lock(Unknown Source)
    java.base/jdk.internal.misc.InternalLock.lock(Unknown Source)
    java.base/java.io.BufferedOutputStream.write(Unknown Source)
    java.base/java.io.DataOutputStream.write(Unknown Source) <== monitors:1
    java.base/java.io.ByteArrayOutputStream.writeTo(Unknown Source) <== monitors:1
    com.rabbitmq.client.impl.Frame.writeTo(Frame.java:197)
    com.rabbitmq.client.impl.SocketFrameHandler.writeFrame(SocketFrameHandler.java:209)
    com.rabbitmq.client.impl.AMQConnection.writeFrame(AMQConnection.java:649)
    com.rabbitmq.client.impl.AMQCommand.transmit(AMQCommand.java:150)
    com.rabbitmq.client.impl.AMQChannel.quiescingTransmit(AMQChannel.java:503)
    com.rabbitmq.client.impl.AMQChannel.quiescingTransmit(AMQChannel.java:479)
    com.rabbitmq.client.impl.AMQChannel.quiescingRpc(AMQChannel.java:378)
    com.rabbitmq.client.impl.AMQChannel.rpc(AMQChannel.java:366)
    com.rabbitmq.client.impl.AMQChannel.privateRpc(AMQChannel.java:305)
    com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:152)
    com.rabbitmq.client.impl.ChannelN.queueDeclarePassive(ChannelN.java:1033)
    com.rabbitmq.client.impl.ChannelN.queueDeclarePassive(ChannelN.java:47)
    java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(Unknown Source)
    java.base/java.lang.reflect.Method.invoke(Unknown Source)
    org.springframework.amqp.rabbit.connection.CachingConnectionFactory$CachedChannelInvocationHandler.invoke(CachingConnectionFactory.java:1204)
    jdk.proxy2/jdk.proxy2.$Proxy228.queueDeclarePassive(Unknown Source)
    org.springframework.amqp.rabbit.listener.BlockingQueueConsumer.attemptPassiveDeclarations(BlockingQueueConsumer.java:751)
    org.springframework.amqp.rabbit.listener.BlockingQueueConsumer.passiveDeclarations(BlockingQueueConsumer.java:650)
    org.springframework.amqp.rabbit.listener.BlockingQueueConsumer.start(BlockingQueueConsumer.java:637)
    org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.initialize(SimpleMessageListenerContainer.java:1481)
    org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.run(SimpleMessageListenerContainer.java:1322)
    java.base/java.lang.VirtualThread.run(Unknown Source)

Reproduction steps

1. Spring Boot 3 with spring-amqp
2. JDK 21
3. spring.threads.virtual.enabled=true
4. jvm-debug-flag -Djdk.tracePinnedThreads=full

Expected behavior

no thread pinning

Additional context

it seems the culprits are DataOutputStream & ByteArrayOutputStream.

according to this article, not all java.io classes are adjusted to be fit for project loom. not sure why though. is it possbile to use the compatible classes instead?