BUG: SandboxClassLoader 死锁问题

[aloooha]

jvm-sandbox 安装repeater插件后，发现应用概率性启动卡住，jstack发现死锁，日志如下：

Found one Java-level deadlock:
=============================
"app-monitor-1":
  waiting to lock monitor 0x00007fb4f0003668 (object 0x0000000084f93300, a [I),
  which is held by "main"
"main":
  waiting to lock monitor 0x00007fb4f0004638 (object 0x0000000084d84b88, a com.alibaba.jvm.sandbox.agent.SandboxClassLoader),
  which is held by "sandbox-jetty-qtp-191872762-34"
"sandbox-jetty-qtp-191872762-34":
  waiting to lock monitor 0x00007fb4f0003668 (object 0x0000000084f93300, a [I),
  which is held by "main"

Java stack information for the threads listed above:
===================================================
"app-monitor-1":
	at com.alibaba.jvm.sandbox.core.util.matcher.structure.ClassStructureImplByAsm.<init>(ClassStructureImplByAsm.java:400)
	at com.alibaba.jvm.sandbox.core.util.matcher.structure.ClassStructureFactory.createClassStructure(ClassStructureFactory.java:57)
	at com.alibaba.jvm.sandbox.core.manager.impl.SandboxClassFileTransformer.getClassStructure(SandboxClassFileTransformer.java:64)
	at com.alibaba.jvm.sandbox.core.manager.impl.SandboxClassFileTransformer._transform(SandboxClassFileTransformer.java:117)
	at com.alibaba.jvm.sandbox.core.manager.impl.SandboxClassFileTransformer.transform(SandboxClassFileTransformer.java:84)
	at sun.instrument.TransformerManager.transform(TransformerManager.java:188)
	at sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:428)
	at java.lang.ClassLoader.findBootstrapClass(Native Method)
	at java.lang.ClassLoader.findBootstrapClassOrNull(ClassLoader.java:1008)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:407)
	- locked <0x00000000ead44bb0> (a java.lang.Object)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:405)
	- locked <0x00000000ead44b10> (a java.lang.Object)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:405)
	- locked <0x00000000850144a8> (a com.alibaba.jvm.sandbox.core.classloader.ModuleJarClassLoader)
	at com.alibaba.jvm.sandbox.core.classloader.RoutingURLClassLoader.access$601(RoutingURLClassLoader.java:22)
	at com.alibaba.jvm.sandbox.core.classloader.RoutingURLClassLoader$1.loadClass(RoutingURLClassLoader.java:105)
	at com.alibaba.jvm.sandbox.core.classloader.ClassLoadingLock.loadingInLock(ClassLoadingLock.java:55)
	- locked <0x00000000ead43a28> (a java.lang.Object)
	at com.alibaba.jvm.sandbox.core.classloader.RoutingURLClassLoader.loadClass(RoutingURLClassLoader.java:64)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
	at io.micrometer.core.instrument.distribution.TimeWindowMax.poll(TimeWindowMax.java:85)
	at io.micrometer.prometheus.PrometheusTimer.max(PrometheusTimer.java:97)
	at io.micrometer.core.instrument.AbstractTimer.takeSnapshot(AbstractTimer.java:183)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
"main":
	at com.alibaba.jvm.sandbox.core.util.matcher.structure.ClassStructureImplByAsm.<init>(ClassStructureImplByAsm.java:400)
	at com.alibaba.jvm.sandbox.core.util.matcher.structure.ClassStructureFactory.createClassStructure(ClassStructureFactory.java:57)
	at com.alibaba.jvm.sandbox.core.manager.impl.SandboxClassFileTransformer.getClassStructure(SandboxClassFileTransformer.java:64)
	at com.alibaba.jvm.sandbox.core.manager.impl.SandboxClassFileTransformer._transform(SandboxClassFileTransformer.java:117)
	at com.alibaba.jvm.sandbox.core.manager.impl.SandboxClassFileTransformer.transform(SandboxClassFileTransformer.java:84)
	at sun.instrument.TransformerManager.transform(TransformerManager.java:188)
	at sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:428)
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:756)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:468)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:74)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:369)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:363)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:362)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
	- locked <0x00000000ea700920> (a java.lang.Object)
	at org.springframework.boot.loader.LaunchedURLClassLoader.loadClass(LaunchedURLClassLoader.java:151)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
	at org.hibernate.loader.plan.build.internal.returns.AbstractExpandingFetchSource.buildEntityAttributeFetch(AbstractExpandingFetchSource.java:112)
	at org.hibernate.internal.util.collections.LazyIndexedMap.lockedComputeIfAbsent(LazyIndexedMap.java:77)
	- locked <0x00000000fb807c90> (a org.hibernate.persister.entity.EntityLoaderLazyCollection)
	at org.hibernate.internal.util.collections.LazyIndexedMap.computeIfAbsent(LazyIndexedMap.java:63)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
	- locked <0x0000000081b9fec8> (a java.util.concurrent.ConcurrentHashMap)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583)
	- locked <0x00000000816cee88> (a java.lang.Object)
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:144)
	at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:88)
"sandbox-jetty-qtp-191872762-34":
	at com.alibaba.jvm.sandbox.core.util.matcher.structure.ClassStructureImplByAsm.<init>(ClassStructureImplByAsm.java:400)
	at com.alibaba.jvm.sandbox.core.util.matcher.structure.ClassStructureFactory.createClassStructure(ClassStructureFactory.java:57)
	at com.alibaba.jvm.sandbox.core.manager.impl.SandboxClassFileTransformer.getClassStructure(SandboxClassFileTransformer.java:64)
	at com.alibaba.jvm.sandbox.core.manager.impl.SandboxClassFileTransformer._transform(SandboxClassFileTransformer.java:117)
	at com.alibaba.jvm.sandbox.core.manager.impl.SandboxClassFileTransformer.transform(SandboxClassFileTransformer.java:84)
	at sun.instrument.TransformerManager.transform(TransformerManager.java:188)
	at sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:428)
	at java.lang.ClassLoader.findBootstrapClass(Native Method)
	at java.lang.ClassLoader.findBootstrapClassOrNull(ClassLoader.java:1008)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:407)
	- locked <0x00000000eaa36c60> (a java.lang.Object)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:405)
	- locked <0x00000000eaa36b98> (a java.lang.Object)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:405)
	- locked <0x0000000084d84b88> (a com.alibaba.jvm.sandbox.agent.SandboxClassLoader)
	at com.alibaba.jvm.sandbox.agent.SandboxClassLoader.loadClass(SandboxClassLoader.java:68)
	- locked <0x0000000084d84b88> (a com.alibaba.jvm.sandbox.agent.SandboxClassLoader)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
	at com.xxx.apm.JettyInterceptor.obBefore(JettyInterceptor.java:24)
	at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java)
	at org.eclipse.jetty.server.Server.handle(Server.java:351)
	at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:454)
	at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:534)
	at java.lang.Thread.run(Thread.java:748)

Found 1 deadlock.