RFR: 8035150 ShouldNotReachHere() in ConstantPool::copy_entry_to

[Staffan Larsen]

On 26 feb 2014, at 15:03, Daniel D. Daugherty <daniel.daugherty at oracle.com> wrote:

> On 2/26/14 1:31 AM, Staffan Larsen wrote:
>> On 26 feb 2014, at 01:48, Daniel D. Daugherty <daniel.daugherty at oracle.com> wrote:
>> 
>>> I concur with Markus. Pairing JVM_CONSTANT_UnresolvedClassInError with
>>> JVM_CONSTANT_UnresolvedClass in the ConstantPool::copy_entry_to()
>>> switch looks like the right thing to do.
>> Good - thanks.
>> 
>>> The usual questions:
>>> 
>>> - why wasn't this failure mode seen before JDK8?
>> No tests for this ? ;)
> 
> I should have been more clear... :-) Why hasn't the NetBeans profiler
> run into this before? That profiler is a wonderful test for the
> RedefineClasses/RetransformClasses stuff…

Ah, ok. No idea...

> 
> 
>> 
>>> - was this failure caught somewhere else before JDK8 and changes
>>>  in JDK8 exposed a new code path?
>>> 
>>> Reasoning about this from a 30,000 foot view, I don't see any reason
>>> why you can't redefine a class that has a constant pool ref that
>>> refers to a class in error. You won't be able to use the error'ed
>>> class, but there's no reason it can't be in there... Or does that
>>> violate the rule that you can't redefine a class that isn't fully
>>> linked (what ever that means...)???
>>> 
>>> So what does your new test on JDK7 or JDK6? Just curious…
>> The test passes on jdk7, but fails on jdk8. (I don’t have a jdk6). I don’t know why it passes on jdk7, do you think it’s important to track it down?
> 
> The fact that it passes on JDK7 is the useful piece of data.
> Figuring out why is much less important. BTW, which JDK7
> version? One of the updates or GA/FCS?

I used 7u45, but now I tested with 7u4 as well - passes there, too.

Are you ok with pushing the change?

Thanks,
/Staffan

> 
> Dan
> 
> 
>> 
>> /Staffan
>> 
>>> Dan
>>> 
>>> 
>>> On 2/24/14 2:42 AM, Markus Gronlund wrote:
>>>> Hi Staffan,
>>>> 
>>>> I would think this is the correct fix.
>>>> 
>>>> The other two constant pool "error" tags, besides UnresolvedClassInError, which signal constant pool resolution errors are MethodTypeInError and MethodHandleInError - these error tags are associated with their corresponding "success" tags in switch targets in ConstantPool::copy_entry_to(), as well as in additional routines in constantPool.cpp.
>>>> 
>>>> In addition, in other routines in ConstantPool.cpp, the error tag JVM_CONSTANT_UnresolvedClassInError is associated with JVM_CONSTANT_UnresolvedClass -  ConstantPool::resolve_constant_at_impl() for example.
>>>> 
>>>> Thanks
>>>> Markus
>>>> 
>>>> 
>>>> -----Original Message-----
>>>> From: Staffan Larsen
>>>> Sent: den 21 februari 2014 15:11
>>>> To: hotspot-runtime-dev; serviceability-dev at openjdk.java.net serviceability-dev at openjdk.java.net
>>>> Subject: RFR: 8035150 ShouldNotReachHere() in ConstantPool::copy_entry_to
>>>> 
>>>> This is an attempt to solve a crash while redefining a class that has unresolved class references in its constant pool. I would appreciate some extra scrutiny here since I am unfamiliar with this code path.
>>>> 
>>>> I have also added a test that causes a JVM crash without the fix.
>>>> 
>>>> The updates to the test library is all code copied from the jdk version of the test library.
>>>> 
>>>> webrev: http://cr.openjdk.java.net/~sla/8035150/webrev.00/
>>>> bug: https://bugs.openjdk.java.net/browse/JDK-8035150
>>>> 
>>>> Thanks,
>>>> /Staffan

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