Review request: 8000459: assert(java_lang_String::is_instance(entry)) failure with various mlvm tests

[serguei.spitsyn at oracle.com]

Hi Jiangli,


On 10/10/12 9:37 AM, Jiangli Zhou wrote:
> Hi Serguei,
>
> Thanks for the review! Please see comments below.
>
> On 10/09/2012 06:05 PM, serguei.spitsyn at oracle.com wrote:
>> Hi Jiangli,
>>
>> I'm not very familiar with the pseudo strings, and so, just have a 
>> question:
>>
>> *src/share/vm/prims/jvmtiTagMap.cpp*
>> 2927             entry = pool->resolved_string_at(i);
>> 2928             assert(java_lang_String::is_instance(entry) ||
>> 2929                    pool->is_pseudo_string_at(i), "must be string");
>> I have a little of doubt the above is correct.
>>
>> What value the "entry" will have in a case of pseudo string cp entry?
>> Just want to understand what constant pool reference will be reported.
>> Do you see all related failing tests passed?
>>
>> Would something like the following be more accurate ?
>>    entry = pool->is_pseudo_string_at(i) ?
>>                pool->pseudo_string_at(i, cp_to_object_index(i)) :
>>                pool->resolved_string_at(i);
>> assert(java_lang_String::is_instance(entry));
>>
>> In this case, a reference from CP to string is reported regardless it 
>> is pseudo string or not.
>
> Those are very good questions. Here is an example of the specific case 
> with a generated JSR292 java.lang.invoke.LambdaForm$MH class. The 
> follow are two constant pool entries of the class. Entry 16 is a 
> "sun/misc/Unsafe" String, which could be patched using a 
> sun.misc.Unsafe klass oop.
>
>         ...
>         (0016) tag=Utf8 "sun/misc/Unsafe"
>         (0017) tag=Class "sun/misc/Unsafe"
>         ...
>
> I discussed with John Rose about different ways to fix the assertion 
> issue. The code you have above uses pseudo_string_at() to access the 
> 'entry', which is similar to one of the version we discussed. The 
> current change was chosen as it's the simplest solution.

I'm Ok with the simplest solution.

Thank you for the details!
-Serguei

>
> Thanks,
>
> Jiangli
>>
>>
>> Thanks,
>> Serguei
>>
>> On 10/9/12 4:26 PM, Jiangli Zhou wrote:
>>> Please review following fix for 8000459:
>>>
>>> http://cr.openjdk.java.net/~jiangli/8000459/webrev/
>>>
>>> With JSR292, a constant pool String entry could be patched to a 
>>> non-string oop. The assert in 
>>> VM_HeapWalkOperation::iterate_over_class() needs to be adjusted to 
>>> reflect that.
>>>
>>> Thanks,
>>>
>>> Jiangli
>>
>