Hi Vladimir,
thank you. Of course you're right: I'll dub this issue "Hydra" - one head
chopped off, at least one missed, new ones growing. At least the understanding
improves in each iteration ... ;-)
The proposal as it now is indeed has the risk of leaving a stale cache entry
(placeholder) if species loading or initialisation break. The other solution
that was proposed would have wrapped the class loading and initialisation step
in a try/catch block and rolled back the cache entry for the types string at
hand in case anything went wrong. This, too, could lead to the duplicate
definition error if the same species is requested again.
At the foundation of the problem, there's a code cache that overflows. This is
inside the VM, and, as you notice, not easily addressed. In fact, if the
application creates so many adapters that the VM cache overflows, it suggests a
problem with the application. It's like forcing an OOME by just going mad on
allocations. Thus, I don't see how (1) would help.
I agree that this is a test problem that has never occurred "in the wild". I
also agree that, in case it would, the error message should be clearer.
Proposal - this is a derivative of (3):
* Keep the fix as it is, because it certainly clarifies the cache
initialisation logic.
* Additionally, harden the class loading / initialisation step:
- Wrap it in a try/catch block.
- In case something goes wrong, mark the species as failure in the cache and
raise an appropriate error.
* Also, check for failed species upon retrieval and raise an appropriate error.
* Finally, harden the test itself against such errors, much like it deals with
code cache overflows.
How about it?
Best,
Michael
> Am 28.10.2015 um 13:02 schrieb Vladimir Ivanov <vladimir.x.iva...@oracle.com>:
>
> 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.<init>).
> 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$SpeciesData.<init>(BoundMethodHandle.java:347)
>> at
>> java.lang.invoke.BoundMethodHandle$SpeciesData.getForClass(BoundMethodHandle.java:411)
>> at java.lang.invoke.BoundMethodHandle$Species_IL7.<clinit>(Species_IL7)
>> at sun.misc.Unsafe.ensureClassInitialized(Native Method)
>> at
>> java.lang.invoke.BoundMethodHandle$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 <bootloader>): attempted
>> duplicate class definition for name:
>> "java/lang/invoke/BoundMethodHandle$Species_IL7"
>> 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$5/21979926.run(Unknown Source)
>> at java.lang.Thread.run(Thread.java:745)
>> java.lang.LinkageError: loader (instance of <bootloader>): attempted
>> duplicate class definition for name:
>> "java/lang/invoke/BoundMethodHandle$Species_IL7"
>> 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$5/21979926.run(Unknown Source)
>> at java.lang.Thread.run(Thread.java:745)
>> STATUS:Failed.STATUS:Failed.STATUS:Failed.`main' threw exception:
>> java.lang.LinkageError: loader (instance of <bootloader>): attempted
>> duplicate class definition for name:
>> "java/lang/invoke/BoundMethodHandle$Species_IL7"
>> `main' threw exception: java.lang.LinkageError: loader (instance of
>> <bootloader>): attempted duplicate class definition for name:
>> "java/lang/invoke/BoundMethodHandle$Species_IL7"
>> `main' threw exception: java.lang.InternalError:
>> java.lang.NoSuchMethodException: no such method:
>> java.lang.invoke.MethodHandle.linkToStatic(Object,Object,int,Object,Object,Object,Object,Object,Object,Object,MemberName)Object/invokeStatic
>> java.lang.LinkageError: loader (instance of <bootloader>): attempted
>> duplicate class definition for name:
>> "java/lang/invoke/BoundMethodHandle$Species_IL7"
>> 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)
>> -----
>>
>>
>>
--
<http://www.oracle.com/>
Dr. Michael Haupt | Principal Member of Technical Staff
Phone: +49 331 200 7277 | Fax: +49 331 200 7561
Oracle Java Platform Group | LangTools Team | Nashorn
Oracle Deutschland B.V. & Co. KG, Schiffbauergasse 14 | 14467 Potsdam, Germany
<http://www.oracle.com/commitment> Oracle is committed to developing
practices and products that help protect the environment
