RFR(S): 8131129: Attempt to define a duplicate BMH$Species class (original) (raw)

Peter Levart peter.levart at gmail.com
Wed Oct 28 15:21:09 UTC 2015

Hi Vladimir, I think you are right. The proposed fix alone even increases the chance of duplicate class definition attempts as it delays registration in cache to after whole clinit successfully finishes. I would still keep this initialization rearrangement as it fixes the possible publication race too. If the source of 1st exception is from clinit method execution, then it would be best to skip forced class initialization and delay it to its 1st use. Eager initialization does not serve any purpose if the registration into cache is performed out of clinit method as proposed in the fix.

To summarise: the proposed initialization fix would have to be accompanied with removal of forced class initialization to achieve the effect of your option (1) below.

Am I right?

Regards, Peter Michael, Peter,

Thanks for detailed analysis! It was a hard one to track down :-)

Unfortunately, I don't see how the proposed change fixes the problem.

The failure occurs during SpeciesData instantiation (BMH$SpeciesData.). It means updateCache has not yet been called from getForClass:

static SpeciesData getForClass(String types, Class<? extends BoundMethodHandle> clazz) { return updateCache(types, new SpeciesData(types, clazz)); }

With your changes, updateCache is called only after successful loading of a class. So, the cache isn't updated if there was an error during previous attempt.

The real problem is more severe IMO. The loaded class is useless when its initialization finishes abruptly, so there's no way to instantiate it or reload. Right now it is manifested as a duplicate class definition attempt, but if you avoid repeated class loading it will just fail slightly later - the system is already broken and there's no way to recover.

I see the following ways to proceed: (1) delay class initialization (fill in Species_*.SPECIES_DATA field afterwards) and attempt to finish initialization on subsequent requests, but skipping class loading step;

(2) use VM anonymous classes (see JDK-8078602 [1]) and just retry Species creation;

(3) give up on that particular Species shape and throw an error whenever it is requested (how it works right now, but with more meaningful error message).

I remember I experimented with (2), but even after JDK-8078629 [2] there was still measurable peak performance regression on Octane/Nashorn.

(1) looks more favorable and robust, but right now there shouldn't be much difference - there's no support in VM to unload MH.linkTo* adapters, so the failure will repeatedly occur once the code cache is full.

My conclusion is that it is mostly a test problem, but java.lang.invoke framework should clearly communicate the reason why it fails. Since the test is aware about code cache overflow problems, it looks preferable to go with (1) or (3) for now. VM should throw VirtualMachineError on repeated attempts to instantiate SPECIES_DATA and the test already filters them out.

Best regards, Vladimir Ivanov

[1] https://bugs.openjdk.java.net/browse/JDK-8078602 [2] https://bugs.openjdk.java.net/browse/JDK-8078629

On 10/28/15 12:19 PM, Michael Haupt wrote:

Dear all,

please review this change. Bug: https://bugs.openjdk.java.net/browse/JDK-8131129 Webrev: http://cr.openjdk.java.net/~mhaupt/8131129/webrev.00/ Thanks to Peter Levart, who has contributed the actual code to fix the issue. The background of this is as follows. Bug 8131129 is an intermittent failure in a multi-threaded test for LambdaForm caching. The failure was not reproducible but used to occur on various platforms every now and then. I was able to dig up some stack traces that reveal the real cause in internal test logs. These traces finally confirmed a suspicion that both Peter and I had had but could, for lack of complete failure information, not pin down as the cause of the issue. (Most traces from failures of the test were only partial, as the test harness is selective about traces it logs.) At the heart of the problem is an overflowing code cache for adapters in the VM. The test, dynamically generating considerable amounts of LambdaForm and BoundMethodHandle species classes, would eventually trigger this overflow. The place at which the problem would surface is this, in BoundMethodHandle.Factory.generateConcreteBMHClass(): Class<? extends BoundMethodHandle> bmhClass = //UNSAFE.defineAnonymousClass(BoundMethodHandle.class, classFile, null).asSubclass(BoundMethodHandle.class); UNSAFE.defineClass(className, classFile, 0, classFile.length, BoundMethodHandle.class.getClassLoader(), null) .asSubclass(BoundMethodHandle.class); UNSAFE.ensureClassInitialized(bmhClass); The test would generate a BMH species with a given type signature via defineClass and immediately thereafter force initialisation of that class, in the course of which a SpeciesData instance is supposed to be created and entered in the BMH species cache. In case the VM's adapter code cache overflowed during this operation, the BMH species' class initialiser would not finish its execution properly, leading to a stale placeholder entry left behind in the cache. The presence of this very placeholder would trick the next request for a BMH species with the same type signature into believing the class needed to be defined, leading to the observed failure. An exemplary stack trace is appended below. Both Peter and I had come up with solutions, but I think Peter's is better as it gets rid of the somewhat intricate and semi-hidden cache registration call made from generated code. With Peter's fix, it's all visible in library code now. Thanks, Michael

----- java.lang.InternalError: java.lang.NoSuchMethodException: no such method: java.lang.invoke.MethodHandle.linkToStatic(Object,Object,int,Object,Object,Object,Object,Object,Object,Object,MemberName)Object/invokeStatic at java.lang.invoke.MethodHandleStatics.newInternalError(MethodHandleStatics.java:120) at java.lang.invoke.DirectMethodHandle.makePreparedLambdaForm(DirectMethodHandle.java:214) at java.lang.invoke.DirectMethodHandle.preparedLambdaForm(DirectMethodHandle.java:188) at java.lang.invoke.DirectMethodHandle.preparedLambdaForm(DirectMethodHandle.java:177) at java.lang.invoke.DirectMethodHandle.make(DirectMethodHandle.java:84) at java.lang.invoke.MethodHandles$Lookup.getDirectMethodCommon(MethodHandles.java:1655) at java.lang.invoke.MethodHandles$Lookup.getDirectMethod(MethodHandles.java:1600) at java.lang.invoke.MethodHandles$Lookup.findStatic(MethodHandles.java:777) at java.lang.invoke.BoundMethodHandle$Factory.makeCbmhCtor(BoundMethodHandle.java:817) at java.lang.invoke.BoundMethodHandle$Factory.makeCtors(BoundMethodHandle.java:772) at java.lang.invoke.BoundMethodHandle$SpeciesData.(BoundMethodHandle.java:347) at java.lang.invoke.BoundMethodHandle$SpeciesData.getForClass(BoundMethodHandle.java:411) at java.lang.invoke.BoundMethodHandle$SpeciesIL7.(SpeciesIL7) at sun.misc.Unsafe.ensureClassInitialized(Native Method) at java.lang.invoke.BoundMethodHandle$Factory.generateConcreteBMHClass(BoundMethodHandle.java:718) at java.lang.invoke.BoundMethodHandle$SpeciesData.get(BoundMethodHandle.java:401) at java.lang.invoke.BoundMethodHandle$SpeciesData.extendWith(BoundMethodHandle.java:388) at java.lang.invoke.LambdaFormEditor.newSpeciesData(LambdaFormEditor.java:363) at java.lang.invoke.LambdaFormEditor.makeArgumentCombinationForm(LambdaFormEditor.java:631) at java.lang.invoke.LambdaFormEditor.filterArgumentForm(LambdaFormEditor.java:612) at java.lang.invoke.MethodHandles.filterArgument(MethodHandles.java:2667) at java.lang.invoke.MethodHandles.filterArguments(MethodHandles.java:2654) at TestMethods$4.getMH(TestMethods.java:180) at TestMethods.getTestCaseMH(TestMethods.java:548) at LFMultiThreadCachingTest.lambda$doTest$0(LFMultiThreadCachingTest.java:80) at LFMultiThreadCachingTest$$Lambda$5/21979926.run(Unknown Source) at java.lang.Thread.run(Thread.java:745) Caused by: java.lang.NoSuchMethodException: no such method: java.lang.invoke.MethodHandle.linkToStatic(Object,Object,int,Object,Object,Object,Object,Object,Object,Object,MemberName)Object/invokeStatic at java.lang.invoke.MemberName.makeAccessException(MemberName.java:873) at java.lang.invoke.MemberName$Factory.resolveOrFail(MemberName.java:990) at java.lang.invoke.DirectMethodHandle.makePreparedLambdaForm(DirectMethodHandle.java:212) ... 25 more Caused by: java.lang.NoSuchMethodError: java.lang.invoke.MethodHandle.linkToStatic(Ljava/lang/Object;Ljava/lang/Object;ILjava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/invoke/MemberName;)Ljava/lang/Object; at java.lang.invoke.MethodHandleNatives.resolve(Native Method) at java.lang.invoke.MemberName$Factory.resolve(MemberName.java:962) at java.lang.invoke.MemberName$Factory.resolveOrFail(MemberName.java:987) ... 26 more Caused by: java.lang.VirtualMachineError: out of space in CodeCache for method handle intrinsic ... 29 more java.lang.LinkageError: loader (instance of ): attempted duplicate class definition for name: "java/lang/invoke/BoundMethodHandle$SpeciesIL7" at sun.misc.Unsafe.defineClass(Native Method) at java.lang.invoke.BoundMethodHandle$Factory.generateConcreteBMHClass(BoundMethodHandle.java:715) at java.lang.invoke.BoundMethodHandle$SpeciesData.get(BoundMethodHandle.java:401) at java.lang.invoke.BoundMethodHandle$SpeciesData.extendWith(BoundMethodHandle.java:388) at java.lang.invoke.LambdaFormEditor.newSpeciesData(LambdaFormEditor.java:363) at java.lang.invoke.LambdaFormEditor.makeArgumentCombinationForm(LambdaFormEditor.java:631) at java.lang.invoke.LambdaFormEditor.filterArgumentForm(LambdaFormEditor.java:612) at java.lang.invoke.MethodHandles.filterArgument(MethodHandles.java:2667) at java.lang.invoke.MethodHandles.filterArguments(MethodHandles.java:2654) at TestMethods$4.getMH(TestMethods.java:180) at TestMethods.getTestCaseMH(TestMethods.java:548) at LFMultiThreadCachingTest.lambda$doTest$0(LFMultiThreadCachingTest.java:80) at LFMultiThreadCachingTest$$Lambda$5/21979926.run(Unknown Source) at java.lang.Thread.run(Thread.java:745) java.lang.LinkageError: loader (instance of ): attempted duplicate class definition for name: "java/lang/invoke/BoundMethodHandle$SpeciesIL7" at sun.misc.Unsafe.defineClass(Native Method) at java.lang.invoke.BoundMethodHandle$Factory.generateConcreteBMHClass(BoundMethodHandle.java:715) at java.lang.invoke.BoundMethodHandle$SpeciesData.get(BoundMethodHandle.java:401) at java.lang.invoke.BoundMethodHandle$SpeciesData.extendWith(BoundMethodHandle.java:388) at java.lang.invoke.LambdaFormEditor.newSpeciesData(LambdaFormEditor.java:363) at java.lang.invoke.LambdaFormEditor.makeArgumentCombinationForm(LambdaFormEditor.java:631) at java.lang.invoke.LambdaFormEditor.filterArgumentForm(LambdaFormEditor.java:612) at java.lang.invoke.MethodHandles.filterArgument(MethodHandles.java:2667) at java.lang.invoke.MethodHandles.filterArguments(MethodHandles.java:2654) at TestMethods$4.getMH(TestMethods.java:180) at TestMethods.getTestCaseMH(TestMethods.java:548) at LFMultiThreadCachingTest.lambda$doTest$0(LFMultiThreadCachingTest.java:80) at LFMultiThreadCachingTest$$Lambda$5/21979926.run(Unknown Source) at java.lang.Thread.run(Thread.java:745) STATUS:Failed.STATUS:Failed.STATUS:Failed.main' threw exception:_ _java.lang.LinkageError: loader (instance of <bootloader>): attempted_ _duplicate class definition for name:_ _"java/lang/invoke/BoundMethodHandle$SpeciesIL7"_ _main' threw exception: java.lang.LinkageError: loader (instance of ): attempted duplicate class definition for name: "java/lang/invoke/BoundMethodHandle$SpeciesIL7" `main' threw exception: java.lang.InternalError: java.lang.NoSuchMethodException: no such method: java.lang.invoke.MethodHandle.linkToStatic(Object,Object,int,Object,Object,Object,Object,Object,Object,Object,MemberName)Object/invokeStatic java.lang.LinkageError: loader (instance of ): attempted duplicate class definition for name: "java/lang/invoke/BoundMethodHandle$SpeciesIL7" at sun.misc.Unsafe.defineClass(Native Method) at java.lang.invoke.BoundMethodHandle$Factory.generateConcreteBMHClass(BoundMethodHandle.java:715) at java.lang.invoke.BoundMethodHandle$SpeciesData.get(BoundMethodHandle.java:401) -----

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