RFR (XS): 8023004: JSR 292: java.lang.RuntimeException: Original target method was called.

[Vladimir Ivanov]

http://cr.openjdk.java.net/~vlivanov/8023004/webrev.01/
3 lines changed: 0 ins; 2 del; 1 mod

Reviewed-by: jrose, ?

The fix is to skip MemberNameTable update in MHN_getMemberVMInfo.

I filed a followup bug to implement MemberName interning [1]. It should 
eliminate possibility of MemberNameTable elements overwrite.

Testing: failing testcase.

Contributed-by: sspitsyn

JBS:  https://bugs.openjdk.java.net/browse/JDK-8023004

Best regards,
Vladimir Ivanov

[1] https://bugs.openjdk.java.net/browse/JDK-8027162

On 10/18/13 8:47 PM, Christian Thalinger wrote:
>
> On Oct 18, 2013, at 1:25 AM, serguei.spitsyn at oracle.com wrote:
>
>> Vladimir,
>>
>>
>> Just want to share some details with you.
>>
>>
>> On 10/17/13 5:46 AM, Vladimir Ivanov wrote:
>>> Serguei, Chris, Igor, thanks for looking at this fix.
>>>
>>> I need to look more thoroughly at this code.
>>> I assumed that member name is initialized only once, but I was wrong - asserting empty slot in MethodHandles::init_method_MemberName fails during initialization of JSR292 core classes.
>>
>> John or Chris, please, correct me if I'm wrong...
>> But, I think, John had a plan in mind to utilize the MNT for uniqueness of member names.
>> It was about all member names, not only method member names.
>
> Correct.  It is worrying that the assert fires.  We should get to the bottom of this and fix it properly.
>
>>
>>
>> Thanks,
>> Serguei
>>
>>>
>>> Best regards,
>>> Vladimir Ivanov
>>>
>>> On 10/17/13 1:39 PM, serguei.spitsyn at oracle.com wrote:
>>>> On 10/16/13 1:28 PM, Christian Thalinger wrote:
>>>>> On Oct 14, 2013, at 12:15 PM, Vladimir Ivanov
>>>>> <vladimir.x.ivanov at oracle.com> wrote:
>>>>>
>>>>>> http://cr.openjdk.java.net/~vlivanov/8023004/webrev.00/
>>>>>> 7 lines changed: 5 ins; 1 del; 1 mod
>>>>>>
>>>>>> Assertion code in JDK fetches info from VM using MHN.getMemberVMInfo:
>>>>>> assert(m.vminfoIsConsistent());
>>>>>>
>>>>>> After that check, class redefinition is broken - it's still possible
>>>>>> to invoke old version of a method.
>>>>>>
>>>>>> Analysis from Serguei:
>>>>>> "The problem is here:
>>>>>> oop MethodHandles::init_method_MemberName(Handle mname, CallInfo&
>>>>>> info) {
>>>>>>   . . . . . . . .
>>>>>> m->method_holder()->add_member_name(m->method_idnum(), mname);
>>>>>>
>>>>>>   return mname();
>>>>>> }
>>>>>>
>>>>>> The call to add_member_name() resets the member name at the index
>>>>>> m->method_idnum(). After that one of the two member names with the
>>>>>> same method_idnum() is out of the MNT and is not updated when the
>>>>>> method is redefined."
>>>>> As I understand this the problem is calling
>>>>> MethodHandles::init_method_MemberName which installs a new MemberName
>>>>> instance in the MemberNameTable.  Correct?
>>>>>
>>>>> If that's the case then there is a potential race here.
>>>>>
>>>>> +     x = m->method_holder()->get_member_name(m->method_idnum());
>>>>> +     if (x == NULL) {
>>>>> +       Handle mname2 = MethodHandles::new_MemberName(CHECK_NULL);
>>>>>          x = MethodHandles::init_method_MemberName(mname2, info);
>>>>>        }
>>>>>
>>>>> Racing threads can get back null when calling get_member_name and then
>>>>> install different MemberName objects in the table.
>>>>
>>>> Good catch, Chris.
>>>> I do not see a way to fix it easily without some refactoring.
>>>>
>>>> It is probably better to add to the InstanceKlass a helper function that
>>>> will do
>>>> this dance with a required synchronization.
>>>> But the following line needs to be taken out of the
>>>> init_method_MemberName() :
>>>> m->method_holder()->add_member_name(m->method_idnum(), mname);
>>>>
>>>>
>>>> Thanks,
>>>> Serguei
>>>>
>>>>>
>>>>>> The fix is to check whether there's already a member name associated
>>>>>> with the before creating a new one.
>>>>>>
>>>>>> Testing: failing test.
>>>>>>
>>>>>> Contributed-by: sspitsyn, vlivanov
>>>>>>
>>>>>> Best regards,
>>>>>> Vladimir Ivanov
>>>>>>
>>>>>> JBS: https://bugs.openjdk.java.net/browse/JDK-8023004
>>>>
>>
>