RFR(XS): 8144852: Corrupted oop in nmethod

[Dean Long]

Thanks Vladimir.

dl

On 12/17/2015 5:07 AM, Vladimir Ivanov wrote:
>> Vladimir, are you OK with keeping the changes in method?  If so, I will
>> push what I have.
> I'm fine with leaving oopDesc::print_* as is.
>
> Best regards,
> Vladimir Ivanov
>
>> On 12/16/2015 3:38 PM, Ioi Lam wrote:
>>> Currently non_oop_word is used only in the nmethod code. If this value
>>> is assigned to an oop or a metadata* elsewhere we would probably see
>>> massive crashes. Adding non_oop_word to oopDesc::print_*_on would
>>> imply that it's OK to assign this value in a more general context,
>>> which is not true.
>>>
>>> So I would suggest keeping knowledge of non_oop_word inside nmethod
>>> for now, and we can revisit this if other places start to use
>>> non_oop_word.
>>>
>>> Thanks
>>> - Ioi
>>>
>>> On 12/16/15 12:41 PM, Dean Long wrote:
>>>> Ping.
>>>>
>>>> Could runtime folks please comment on Vladimir's suggestion to have
>>>> oopDesc::print_*_on and
>>>> Metadata::print_*_maybe_null support Universe::non_oop_word() values
>>>> without crashing, or if I should keep this change in nmethod only.
>>>>
>>>> thanks,
>>>>
>>>> dl
>>>>
>>>> On 12/11/2015 11:18 AM, Dean Long wrote:
>>>>> [adding hotspot-runtime-dev]
>>>>>
>>>>> On 12/11/2015 3:49 AM, Vladimir Ivanov wrote:
>>>>>> Dean, thanks for taking care of it.
>>>>>>
>>>>>> Can oopDesc::print_value_on and print_value_on_maybe_null be
>>>>>> enhanced instead to handle non_oop_word case (in addition to NULL
>>>>>> case)?
>>>>>>
>>>>>
>>>>> I thought of that, but didn't want to add
>>>>> print_value_on_maybe_null_or_non_oop :-)
>>>>>
>>>>> If you feel strongly about that, then I should probably get input
>>>>> from runtime too, since I think they own that code.
>>>>>
>>>>>> Also, the following is slightly misleading since metadata pointers
>>>>>> aren't oops:
>>>>>>  void nmethod::print_recorded_metadata() {
>>>>>> +    if (m == (Metadata*)Universe::non_oop_word()) {
>>>>>> +      tty->print("non-oop word");
>>>>>>
>>>>>
>>>>> Would "non-metadata word" be better?
>>>>>
>>>>> dl
>>>>>
>>>>>> Best regards,
>>>>>> Vladimir Ivanov
>>>>>>
>>>>>> On 12/11/15 6:36 AM, Dean Long wrote:
>>>>>>> https://bugs.openjdk.java.net/browse/JDK-8144852
>>>>>>> http://cr.openjdk.java.net/~dlong//8144852/webrev/
>>>>>>>
>>>>>>> The fix for [1] introduced new functions 
>>>>>>> nmethod::print_recorded_oops
>>>>>>> and nmethod::print_recorded_metadata that print all oop and 
>>>>>>> metadata
>>>>>>> values in an nmethod.  Currently NULL values are handled OK, but
>>>>>>> Universe::non_oop_word values cause a crash.
>>>>>>>
>>>>>>> (This bug is marked confidential because it was reported against
>>>>>>> one of
>>>>>>> our closed ports.)
>>>>>>>
>>>>>>> dl
>>>>>>>
>>>>>>> [1]     JDK-8072008: Emit direct call instead of linkTo* for
>>>>>>> recursive
>>>>>>> indy/MH.invoke* calls
>>>>>
>>>>
>>>
>>