RFR(M): 8081674: EmptyStackException at startup if running with extended or unsupported charset
Volker Simonis
volker.simonis at gmail.com
Tue Jun 9 17:09:04 UTC 2015
Hi Mandy,
thanks for looking into this.
Uunfortunately your fix only helps to fix "java -version" :(
Running even a minimal HelloWorld will still fail with the following
stack trace which is still caused by the same EmptyStackException:
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.ExceptionInInitializerError
at sun.misc.Unsafe.ensureClassInitialized(Native Method)
at sun.misc.SharedSecrets.getJavaUtilZipFileAccess(SharedSecrets.java:158)
at sun.misc.URLClassPath$JarLoader.<clinit>(URLClassPath.java:765)
at sun.misc.URLClassPath$3.run(URLClassPath.java:530)
at sun.misc.URLClassPath$3.run(URLClassPath.java:520)
at java.security.AccessController.doPrivileged(Native Method)
at sun.misc.URLClassPath.getLoader(URLClassPath.java:519)
at sun.misc.URLClassPath.getLoader(URLClassPath.java:492)
at sun.misc.URLClassPath.getNextLoader(URLClassPath.java:457)
at sun.misc.URLClassPath.access$100(URLClassPath.java:64)
at sun.misc.URLClassPath$1.next(URLClassPath.java:239)
at sun.misc.URLClassPath$1.hasMoreElements(URLClassPath.java:250)
at java.net.URLClassLoader$3$1.run(URLClassLoader.java:601)
at java.net.URLClassLoader$3$1.run(URLClassLoader.java:599)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader$3.next(URLClassLoader.java:598)
at java.net.URLClassLoader$3.hasMoreElements(URLClassLoader.java:623)
at sun.misc.CompoundEnumeration.next(CompoundEnumeration.java:45)
at sun.misc.CompoundEnumeration.hasMoreElements(CompoundEnumeration.java:54)
at sun.misc.CompoundEnumeration.next(CompoundEnumeration.java:45)
at sun.misc.CompoundEnumeration.hasMoreElements(CompoundEnumeration.java:54)
at java.util.ServiceLoader$LazyIterator.hasNextService(ServiceLoader.java:354)
at java.util.ServiceLoader$LazyIterator.hasNext(ServiceLoader.java:393)
at java.util.ServiceLoader$1.hasNext(ServiceLoader.java:474)
at java.nio.charset.Charset$1.getNext(Charset.java:350)
at java.nio.charset.Charset$1.hasNext(Charset.java:365)
at java.nio.charset.Charset$2.run(Charset.java:410)
at java.nio.charset.Charset$2.run(Charset.java:407)
at java.security.AccessController.doPrivileged(Native Method)
at java.nio.charset.Charset.lookupViaProviders(Charset.java:406)
at java.nio.charset.Charset.lookup2(Charset.java:477)
at java.nio.charset.Charset.lookup(Charset.java:464)
at java.nio.charset.Charset.isSupported(Charset.java:505)
at sun.launcher.LauncherHelper.makePlatformString(LauncherHelper.java:580)
Caused by: java.util.EmptyStackException
at java.util.Stack.peek(Stack.java:102)
at java.lang.ClassLoader$NativeLibrary.getFromClass(ClassLoader.java:1759)
at java.lang.ClassLoader$NativeLibrary.findBuiltinLib(Native Method)
at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1870)
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1843)
at java.lang.Runtime.loadLibrary0(Runtime.java:870)
at java.lang.System.loadLibrary(System.java:1122)
at java.util.zip.ZipFile.<clinit>(ZipFile.java:86)
... 34 more
It's obvious that the way jni_FindClass is looking for the class
context by calling the NativeLibrary::getFromClass method is hacky but
I think that the proposed fix is the quite simple and non-intrusive.
And we probably don't want a complete rework of this code for 8
anyway. So why not fix it the proposed way in 8 and 9 for now? That
will still leave us time to come up with a better clean-up at least
for 9.
What do you think?
Regards,
Volker
On Tue, Jun 9, 2015 at 1:35 AM, Mandy Chung <mandy.chung at oracle.com> wrote:
> Hi Volker,
>
> Your patch reminds me the question I have about loading zip library.
>
> In JDK 9 (and earlier release), zip library is loaded by the VM during
> startup (see ClassLoader::load_zip_library). I think loadLibrary("zip") is
> no longer needed to be called from System::initializeSystemClass method and
> instead it can be loaded by java.util.zip.ZipFile static initializer.
>
> Do you mind to try the patch (below)? That may be a simpler fix.
>
> I never like the way jni_FindClass to look for the class context by calling
> the NativeLibrary::getFromClass method. I will have to look deeper other
> alternative to clean that up. If taking out loadLibrary("zip") resolves
> your issue, this will give us time to come up with a better clean-up in the
> future.
>
> Mandy
> [1] https://bugs.openjdk.java.net/browse/JDK-4429040
>
> diff --git a/src/share/classes/java/lang/System.java
> b/src/share/classes/java/lang/System.java
> --- a/src/share/classes/java/lang/System.java
> +++ b/src/share/classes/java/lang/System.java
> @@ -1192,10 +1192,6 @@
> setOut0(newPrintStream(fdOut,
> props.getProperty("sun.stdout.encoding")));
> setErr0(newPrintStream(fdErr,
> props.getProperty("sun.stderr.encoding")));
>
> - // Load the zip library now in order to keep java.util.zip.ZipFile
> - // from trying to use itself to load this library later.
> - loadLibrary("zip");
> -
> // Setup Java signal handlers for HUP, TERM, and INT (where
> available).
> Terminator.setup();
>
> diff --git a/src/share/classes/java/util/zip/ZipFile.java
> b/src/share/classes/java/util/zip/ZipFile.java
> --- a/src/share/classes/java/util/zip/ZipFile.java
> +++ b/src/share/classes/java/util/zip/ZipFile.java
> @@ -83,6 +83,7 @@
>
> static {
> /* Zip library is loaded from System.initializeSystemClass */
> + System.loadLibrary("zip");
> initIDs();
>
> }
>
>
>
> On 06/08/2015 07:23 AM, Volker Simonis wrote:
>>
>> Hi,
>>
>> can I please get a review at least for the part of this fix which is
>> common for jdk8 and jdk9. It's only a few lines in
>> src/share/vm/prims/jni.cpp for the hotspot repository and one line
>> src/java.base/share/classes/java/lang/ClassLoader.java for the jdk
>> repository.
>>
>> Thanks,
>> Volker
>>
>>
>> On Tue, Jun 2, 2015 at 6:12 PM, Volker Simonis <volker.simonis at gmail.com>
>> wrote:
>>>
>>> Hi,
>>>
>>> can I please have review (and a sponsor) for these changes:
>>>
>>> https://bugs.openjdk.java.net/browse/JDK-8081674
>>> http://cr.openjdk.java.net/~simonis/webrevs/2015/8081674.jdk
>>> http://cr.openjdk.java.net/~simonis/webrevs/2015/8081674.hs
>>>
>>> Please notice that the fix requires synchronous changes in the jdk and
>>> the
>>> hotspot forest.
>>>
>>> The changes themselves are by far not that big as this explanation but I
>>> found the problem to be quite intricate so I tried to explain it as good
>>> as
>>> I could. I'd suggest to read the HTML-formatted explanation in the webrev
>>> although the content is equal to the one in this mail:
>>>
>>> Using an unsupported character encoding (e.g. vi_VN.TCVN on Linux)
>>> results
>>> in an immediate VM failure with jdk 8 and 9:
>>>
>>> export LANG=vi_VN.TCVN
>>> java -version
>>> Error occurred during initialization of VM
>>> java.util.EmptyStackException
>>> at java.util.Stack.peek(Stack.java:102)
>>> at
>>> java.lang.ClassLoader$NativeLibrary.getFromClass(ClassLoader.java:1751)
>>> at java.lang.ClassLoader$NativeLibrary.findBuiltinLib(Native
>>> Method)
>>> at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1862)
>>> at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1835)
>>> at java.lang.Runtime.loadLibrary0(Runtime.java:870)
>>> at java.lang.System.loadLibrary(System.java:1119)
>>> at java.lang.System.initializeSystemClass(System.java:1194)
>>>
>>> This is a consequence of "8005716: Enhance JNI specification to allow
>>> support of static JNI libraries in Embedded JREs".
>>>
>>> With jdk 9 we get this error even if we're running with a supported
>>> charset
>>> which is in the ExtendedCharsets (as opposed to being in the
>>> StandardCharsets) class which is a consequence of delegating the loading
>>> of
>>> the ExtendedCharsets class to the ServiceLoader in jdk 9.
>>>
>>> export LANG=eo.iso-8859-3
>>> output-jdk9/images/jdk/bin/java -version
>>> Error occurred during initialization of VM
>>> java.util.EmptyStackException
>>> at java.util.Stack.peek(Stack.java:102)
>>> at
>>> java.lang.ClassLoader$NativeLibrary.getFromClass(ClassLoader.java:1737)
>>> at java.lang.ClassLoader$NativeLibrary.findBuiltinLib(Native
>>> Method)
>>> at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1866)
>>> at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1840)
>>> at java.lang.Runtime.loadLibrary0(Runtime.java:874)
>>> at java.lang.System.loadLibrary(System.java:1111)
>>> at java.lang.System.initializeSystemClass(System.java:1186)
>>>
>>> Here's why the exception happens for an unsupported charset (see the
>>> mixed
>>> stack trace below for the full details):
>>>
>>> java.lang.System.loadLibrary() wants to load libzip.so. It calls
>>> java.lang.Runtime.loadLibrary0() which at the very beginning calls the
>>> native method ClassLoader$NativeLibrary.findBuiltinLib() which checks if
>>> the
>>> corresponding library is already statically linked into the VM
>>> (introduced
>>> by 8005716).
>>> Java_java_lang_ClassLoader_00024NativeLibrary_findBuiltinLib(),
>>> the native implementation of findBuiltinLib() in Classloader.c calls
>>> GetStringPlatformChars() to convert the library name into the native
>>> platform encoding. GetStringPlatformChars() calls the helper function
>>> jnuEncodingSupported() to check if the platform encoding which is stored
>>> in
>>> the property "sun.jnu.encoding" is supported by Java.
>>> jnuEncodingSupported()
>>> is implemented as follows:
>>>
>>> static jboolean isJNUEncodingSupported = JNI_FALSE;
>>> static jboolean jnuEncodingSupported(JNIEnv *env) {
>>> jboolean exe;
>>> if (isJNUEncodingSupported == JNI_TRUE) {
>>> return JNI_TRUE;
>>> }
>>> isJNUEncodingSupported = (jboolean) JNU_CallStaticMethodByName (
>>> env, &exe,
>>> "java/nio/charset/Charset",
>>> "isSupported",
>>> "(Ljava/lang/String;)Z",
>>> jnuEncoding).z;
>>> return isJNUEncodingSupported;
>>> }
>>>
>>> Once the function finds that the platform encoding is supported (by
>>> calling
>>> java.nio.charset.Charset.isSupported()) it caches this value and always
>>> returns it on following calls. However if the platform encoding is not
>>> supported, it ALWAYS calls java.nio.charset.Charset.isSupported() an
>>> every
>>> subsequent invocation.
>>>
>>> In order to call the Java method Charset.isSupported() (in
>>> JNU_CallStaticMethodByName() in file jni_util.c), we have to call
>>> jni_FindClass() to convert the symbolic class name
>>> "java.nio.charset.Charset" into a class reference.
>>>
>>> But unfortunately, jni_FindClass() (from jni.cpp in libjvm.so) has a
>>> special
>>> handling if called from java.lang.ClassLoader$NativeLibrary to ensure
>>> that
>>> JNI_OnLoad/JNI_OnUnload are executed in the correct class context:
>>>
>>> instanceKlassHandle k (THREAD, thread->security_get_caller_class(0));
>>> if (k.not_null()) {
>>> loader = Handle(THREAD, k->class_loader());
>>> // Special handling to make sure JNI_OnLoad and JNI_OnUnload are
>>> executed
>>> // in the correct class context.
>>> if (loader.is_null() &&
>>> k->name() == vmSymbols::java_lang_ClassLoader_NativeLibrary()) {
>>> JavaValue result(T_OBJECT);
>>> JavaCalls::call_static(&result, k,
>>> vmSymbols::getFromClass_name(),
>>> vmSymbols::void_class_signature(),
>>> thread);
>>> if (HAS_PENDING_EXCEPTION) {
>>> Handle ex(thread, thread->pending_exception());
>>> CLEAR_PENDING_EXCEPTION;
>>> THROW_HANDLE_0(ex);
>>> }
>>>
>>> So if that's the case and jni_FindClass() was reallycalled from
>>> ClassLoader$NativeLibrary, then jni_FindClass() calles
>>> ClassLoader$NativeLibrary().getFromClass() to find out the corresponding
>>> context class which is supposed to be saved there in a field of type
>>> java.util.Stack named "nativeLibraryContext":
>>>
>>> // Invoked in the VM to determine the context class in
>>> // JNI_Load/JNI_Unload
>>> static Class<?> getFromClass() {
>>> return ClassLoader.nativeLibraryContext.peek().fromClass;
>>> }
>>>
>>> Unfortunately, "nativeLibraryContext" doesn't contain any entry at this
>>> point and the invocation of Stack.peek() will throw the exception shown
>>> before. In general, the "nativeLibraryContext" stack will be filled later
>>> on
>>> in Runtime.loadLibrary0() like this:
>>>
>>> NativeLibrary lib = new NativeLibrary(fromClass, name, isBuiltin);
>>> nativeLibraryContext.push(lib);
>>> try {
>>> lib.load(name, isBuiltin);
>>> } finally {
>>> nativeLibraryContext.pop();
>>> }
>>>
>>> such that it always contains at least one element later when
>>> jni_FindClass()
>>> will be invoked.
>>>
>>> So in summary, the problem is that the implementors of 8005716 didn't
>>> took
>>> into account that calling ClassLoader$NativeLibrary.findBuiltinLib() may
>>> trigger a call to jni_FindClass() if we are running on a system with an
>>> unsupported character encoding.
>>>
>>> I'd suggest the following fix for this problem:
>>>
>>> Change ClassLoader$NativeLibrary().getFromClass() to return null if the
>>> stack is empty instead of throwing an exception:
>>>
>>> static Class<?> getFromClass() {
>>> return ClassLoader.nativeLibraryContext.empty() ?
>>> null : ClassLoader.nativeLibraryContext.peek().fromClass;
>>> }
>>>
>>> Unfortunately this also requires a HotSpot change in jni_FindClass() in
>>> order to properly handle the new 'null' return value:
>>>
>>> if (k.not_null()) {
>>> loader = Handle(THREAD, k->class_loader());
>>> // Special handling to make sure JNI_OnLoad and JNI_OnUnload are
>>> executed
>>> // in the correct class context.
>>> if (loader.is_null() &&
>>> k->name() == vmSymbols::java_lang_ClassLoader_NativeLibrary()) {
>>> JavaValue result(T_OBJECT);
>>> JavaCalls::call_static(&result, k,
>>> vmSymbols::getFromClass_name(),
>>> vmSymbols::void_class_signature(),
>>> thread);
>>> if (HAS_PENDING_EXCEPTION) {
>>> Handle ex(thread, thread->pending_exception());
>>> CLEAR_PENDING_EXCEPTION;
>>> THROW_HANDLE_0(ex);
>>> }
>>> oop mirror = (oop) result.get_jobject();
>>> if (oopDesc::is_null(mirror)) {
>>> loader = Handle(THREAD, SystemDictionary::java_system_loader());
>>> } else {
>>> loader = Handle(THREAD,
>>>
>>> InstanceKlass::cast(java_lang_Class::as_Klass(mirror))->class_loader());
>>> protection_domain = Handle(THREAD,
>>>
>>>
>>> InstanceKlass::cast(java_lang_Class::as_Klass(mirror))->protection_domain());
>>> }
>>> }
>>> } else {
>>> // We call ClassLoader.getSystemClassLoader to obtain the system
>>> class
>>> loader.
>>> loader = Handle(THREAD, SystemDictionary::java_system_loader());
>>> }
>>>
>>> These changes are sufficient to solve the problem in Java 8.
>>> Unfortunately,
>>> that's still not enough in Java 9 because there the loading of the
>>> extended
>>> charsets has been delegated to ServiceLoader. But ServiceLoader calls
>>> ClassLoader.getBootstrapResources() which calls
>>> sun.misc.Launcher.getBootstrapClassPath(). This leads to another problem
>>> during class initialization of sun.misc.Launcher if running on an
>>> unsupported locale.
>>>
>>> The first thing done in sun.misc.Launcher.<clinit> is the initialisation
>>> of
>>> the bootstrap URLClassPath in the Launcher. However this initialisation
>>> will
>>> eventually call Charset.isSupported() and if we are running on an
>>> unsupported locale this will inevitably end in another recursive call to
>>> ServiceLoader. But as explained below, ServiceLoader will query the
>>> Launcher's bootstrap URLClassPath which will be still uninitialized at
>>> that
>>> point.
>>>
>>> So we'll have to additionally guard guard against this situation on JDK 9
>>> like this:
>>>
>>> private static Charset lookupExtendedCharset(String charsetName) {
>>> if (!sun.misc.VM.isBooted() || // see
>>> lookupViaProviders()
>>> sun.misc.Launcher.getBootstrapClassPath() == null)
>>> return null;
>>>
>>> This fixes the crashes, but still at the price of not having the extended
>>> charsets available during initialization until
>>> Launcher.getBootstrapClassPath is set up properly. This may be still a
>>> problem if the jdk is installed in a directory which contains characters
>>> specific to an extended encoding or if we have such characters in the
>>> command line arguments.
>>>
>>> Thank you and best regards,
>>> Volker
>>>
>>>
>>> Mixed stack trace of the initial EmptyStackException for unsupported
>>> charsets described before:
>>>
>>> Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native
>>> code)
>>> j java.util.Stack.peek()Ljava/lang/Object;+1
>>> j java.lang.ClassLoader$NativeLibrary.getFromClass()Ljava/lang/Class;+3
>>> v ~StubRoutines::call_stub
>>> V [libjvm.so+0x9d279a] JavaCalls::call_helper(JavaValue*,
>>> methodHandle*,
>>> JavaCallArguments*, Thread*)+0x6b4
>>> V [libjvm.so+0xcad591] os::os_exception_wrapper(void (*)(JavaValue*,
>>> methodHandle*, JavaCallArguments*, Thread*), JavaValue*, methodHandle*,
>>> JavaCallArguments*, Thread*)+0x45
>>> V [libjvm.so+0x9d20cf] JavaCalls::call(JavaValue*, methodHandle,
>>> JavaCallArguments*, Thread*)+0x8b
>>> V [libjvm.so+0x9d1d3b] JavaCalls::call_static(JavaValue*, KlassHandle,
>>> Symbol*, Symbol*, JavaCallArguments*, Thread*)+0x139
>>> V [libjvm.so+0x9d1e3f] JavaCalls::call_static(JavaValue*, KlassHandle,
>>> Symbol*, Symbol*, Thread*)+0x9d
>>> V [libjvm.so+0x9e6588] jni_FindClass+0x428
>>> C [libjava.so+0x20208] JNU_CallStaticMethodByName+0xff
>>> C [libjava.so+0x21cae] jnuEncodingSupported+0x61
>>> C [libjava.so+0x22125] JNU_GetStringPlatformChars+0x125
>>> C [libjava.so+0xedcd]
>>> Java_java_lang_ClassLoader_00024NativeLibrary_findBuiltinLib+0x8b
>>> j
>>>
>>> java.lang.ClassLoader$NativeLibrary.findBuiltinLib(Ljava/lang/String;)Ljava/lang/String;+0
>>> j java.lang.ClassLoader.loadLibrary0(Ljava/lang/Class;Ljava/io/File;)Z+4
>>> j
>>>
>>> java.lang.ClassLoader.loadLibrary(Ljava/lang/Class;Ljava/lang/String;Z)V+228
>>> j
>>> java.lang.Runtime.loadLibrary0(Ljava/lang/Class;Ljava/lang/String;)V+54
>>> j java.lang.System.loadLibrary(Ljava/lang/String;)V+7
>>> j java.lang.System.initializeSystemClass()V+113
>>> v ~StubRoutines::call_stub
>>> V [libjvm.so+0x9d279a] JavaCalls::call_helper(JavaValue*,
>>> methodHandle*,
>>> JavaCallArguments*, Thread*)+0x6b4
>>> V [libjvm.so+0xcad591] os::os_exception_wrapper(void (*)(JavaValue*,
>>> methodHandle*, JavaCallArguments*, Thread*), JavaValue*, methodHandle*,
>>> JavaCallArguments*, Thread*)+0x45
>>> V [libjvm.so+0x9d20cf] JavaCalls::call(JavaValue*, methodHandle,
>>> JavaCallArguments*, Thread*)+0x8b
>>> V [libjvm.so+0x9d1d3b] JavaCalls::call_static(JavaValue*, KlassHandle,
>>> Symbol*, Symbol*, JavaCallArguments*, Thread*)+0x139
>>> V [libjvm.so+0x9d1e3f] JavaCalls::call_static(JavaValue*, KlassHandle,
>>> Symbol*, Symbol*, Thread*)+0x9d
>>> V [libjvm.so+0xe3cceb] call_initializeSystemClass(Thread*)+0xb0
>>> V [libjvm.so+0xe44444]
>>> Threads::initialize_java_lang_classes(JavaThread*,
>>> Thread*)+0x21a
>>> V [libjvm.so+0xe44b12] Threads::create_vm(JavaVMInitArgs*, bool*)+0x4a6
>>> V [libjvm.so+0xa19bd7] JNI_CreateJavaVM+0xc7
>>> C [libjli.so+0xa520] InitializeJVM+0x154
>>> C [libjli.so+0x8024] JavaMain+0xcc
>>>
>>>
>
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