4-th round RFR (XS) 8068162: jvmtiRedefineClasses.cpp: guarantee(false) failed: OLD and/or OBSOLETE method(s) found

[serguei.spitsyn at oracle.com]

Coleen,

Thank you for answering questions below!

Thanks,
Serguei


On 1/19/15 7:55 AM, Coleen Phillimore wrote:
>
> On 1/16/15, 9:24 PM, Daniel D. Daugherty wrote:
>> > 
>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2015/hotspot/8068162-JVMTI-old.4/
>>
>> src/share/vm/memory/universe.hpp
>>     No comments.
>>
>> src/share/vm/memory/universe.cpp
>>     No comments.
>>
>> src/share/vm/prims/jvmtiRedefineClasses.cpp
>>     So redefining the Unsafe class is now very expensive because
>>     we have to visit the i-table and v-table of every class (and
>>     maybe interface?)...
>>
>>     Based on the bug report 'Unsafe::throw_illegal_access' is some
>>     magical method that can appear in any i-table or v-table entry.
>>     Maybe only as part of some default methods thing? That's not
>>     clear to me so I'm just guessing...
>
> True.
>>
>>     Is there some way to limit this visit to classes where the
>>     magical method can appear? Or can it really appear anywhere?
>
> The Unsafe methods can appear in any itable now.   I don't know of a 
> way to limit this.  Fortunately, redefining Unsafe seems to be an 
> unusual thing to do, except for this stress test.
>
> Coleen
>
>>
>> Dan
>>
>>
>> On 1/16/15 12:14 PM, serguei.spitsyn at oracle.com wrote:
>>> Dan, David H. or David C.,
>>>
>>> May I ask one of you to look at the webrev below?
>>> The issue itself is a little bit tricky, so it is not easy to review 
>>> despite the small size.
>>>
>>> Coleen,
>>>
>>> Does the webrev matches what we discussed with you?
>>> Do you give me a thumbs up?
>>>
>>> Thanks,
>>> Serguei
>>>
>>> May I ask
>>>
>>> On 1/13/15 9:47 PM, serguei.spitsyn at oracle.com wrote:
>>>> Please, review the fix for:
>>>>   https://bugs.openjdk.java.net/browse/JDK-8068162
>>>>
>>>>
>>>> Open webrevs:
>>>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2015/hotspot/8068162-JVMTI-old.4/ 
>>>>
>>
>>>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2015/jdk/8068162-Test-IsModifiableAgent/ 
>>>>
>>>>
>>>>
>>>> Summary:
>>>>
>>>>    The sun.misc.Unsafe:throwIllegalAccessError() method is used in 
>>>> place of a default
>>>>    interface method in the itable if a default method was not 
>>>> defined in the interface.
>>>>    In fact, it happens for two interfaces that purhaps are 
>>>> auto-generated:
>>>>      java/nio/CharBuffer
>>>>      java/nio/HeapCharBuffer
>>>>
>>>>    This approach creates a problem when the class sun.misc.Unsafe 
>>>> is retransformed.
>>>>    The Method* pointer to the old (redefined) method in the itable 
>>>> triggers an assert
>>>>    (see the hs_err log in the bug report).
>>>>    Coleen told me that a similar approach is going to be 
>>>> implemented for some vtable entries.
>>>>    Coleen, thanks for suggesting a better fix for this issue!
>>>>
>>>>    The fix is to replace the old Unsafe method in the itable/vtable 
>>>> with the latest method version.
>>>>
>>>>
>>>> Testing:
>>>>   In progress: nsk.jdi.testlist, JTREG java/lang/instrument tests
>>>>
>>>>
>>>> Thanks,
>>>> Serguei
>>>>
>>>
>>
>