Race in java_lang_String::length() when deduplicating

Shenandoah CI reports an assertion failure:

# Internal Error (/home/jenkins/workspace/nightly/shenandoah-jdk/src/hotspot/share/classfile/javaClasses.inline.hpp:78), pid=22355, tid=22358
# assert(oopDesc::equals(value, java_lang_String::value(java_string))) failed: value must be same as java_lang_String::value(java_string)

This seems to be caused by String.value changing concurrently caused by String deduplication.

The call stack is:

Stack: [0x00002b41db723000,0x00002b41db824000], sp=0x00002b41db821120, free space=1016k
Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0xd68c5c] java_lang_String::length(oop, typeArrayOop)+0x32c
V [libjvm.so+0xe83801] jni_GetStringLength+0x2b1
C [libjava.so+0xd6d8] getUTF+0x38
C [libjava.so+0xd9b0] Java_java_lang_ClassLoader_defineClass1+0x100
j java.lang.ClassLoader.defineClass1(Ljava/lang/ClassLoader;Ljava/lang/String;[BIILjava/security/ProtectionDomain;Ljava/lang/String;)Ljava/lang/Class;+0 java.base@13-internal
j java.lang.ClassLoader.defineClass(Ljava/lang/String;[BIILjava/security/ProtectionDomain;)Ljava/lang/Class;+27 java.base@13-internal
j java.security.SecureClassLoader.defineClass(Ljava/lang/String;[BIILjava/security/CodeSource;)Ljava/lang/Class;+12 java.base@13-internal
j jdk.internal.loader.BuiltinClassLoader.defineClass(Ljava/lang/String;Ljdk/internal/loader/Resource;)Ljava/lang/Class;+117 java.base@13-internal
j jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(Ljava/lang/String;)Ljava/lang/Class;+37 java.base@13-internal
j jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(Ljava/lang/String;Z)Ljava/lang/Class;+111 java.base@13-internal
j jdk.internal.loader.BuiltinClassLoader.loadClass(Ljava/lang/String;Z)Ljava/lang/Class;+3 java.base@13-internal
j jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Ljava/lang/String;Z)Ljava/lang/Class;+36 java.base@13-internal
j java.lang.ClassLoader.loadClass(Ljava/lang/String;)Ljava/lang/Class;+3 java.base@13-internal
v ~StubRoutines::call_stub
V [libjvm.so+0xda13bd] JavaCalls::call_helper(JavaValue*, methodHandle const&, JavaCallArguments*, Thread*)+0x74d
V [libjvm.so+0xd9ddfd] JavaCalls::call_virtual(JavaValue*, Klass*, Symbol*, Symbol*, JavaCallArguments*, Thread*)+0x3bd
V [libjvm.so+0xd9e115] JavaCalls::call_virtual(JavaValue*, Handle, Klass*, Symbol*, Symbol*, Handle, Thread*)+0x115
V [libjvm.so+0x16e5197] SystemDictionary::load_instance_class(Symbol*, Handle, Thread*)+0x267
V [libjvm.so+0x16e3ca4] SystemDictionary::resolve_instance_class_or_null(Symbol*, Handle, Handle, Thread*)+0xc34
V [libjvm.so+0x16e3ee2] SystemDictionary::resolve_instance_class_or_null_helper(Symbol*, Handle, Handle, Thread*)+0xa2
V [libjvm.so+0x16e5b0d] SystemDictionary::resolve_or_fail(Symbol*, Handle, Handle, bool, Thread*)+0x4d
V [libjvm.so+0xf015a2] find_class_from_class_loader(JNIEnv_*, Symbol*, unsigned char, Handle, Handle, unsigned char, Thread*)+0x32
V [libjvm.so+0xf0594f] JVM_FindClassFromCaller+0x3af
C [libjava.so+0xd560] Java_java_lang_Class_forName0+0x140
j java.lang.Class.forName0(Ljava/lang/String;ZLjava/lang/ClassLoader;Ljava/lang/Class;)Ljava/lang/Class;+0 java.base@13-internal
j java.lang.Class.forName(Ljava/lang/String;ZLjava/lang/ClassLoader;)Ljava/lang/Class;+43 java.base@13-internal
j sun.launcher.LauncherHelper.loadMainClass(ILjava/lang/String;)Ljava/lang/Class;+93 java.base@13-internal
j sun.launcher.LauncherHelper.checkAndLoadMain(ZILjava/lang/String;)Ljava/lang/Class;+42 java.base@13-internal
v ~StubRoutines::call_stub
V [libjvm.so+0xda13bd] JavaCalls::call_helper(JavaValue*, methodHandle const&, JavaCallArguments*, Thread*)+0x74d
V [libjvm.so+0xe62042] jni_invoke_static(JNIEnv_*, JavaValue*, _jobject*, JNICallType, _jmethodID*, JNI_ArgumentPusher*, Thread*) [clone .isra.178]+0x3c2
V [libjvm.so+0xe888c9] jni_CallStaticObjectMethod+0x1f9
C [libjli.so+0x494c] JavaMain+0x7dc