RFR: 8065634: Crash in InstanceKlass::clean_method_data when _method is NULL

[Stefan Karlsson]

On 2014-12-05 09:04, harold seigel wrote:
> Hi Stefan,
>
> Thanks for restoring the 'else' and the 'nullHandle'.  It looks good!

Thanks!

StefanK

>
> Harold
>
> On 12/5/2014 8:51 AM, Stefan Karlsson wrote:
>> Hi Harold,
>>
>> Thanks for looking at the patch. My first patch used nullHandle and 
>> did the freeing was done inside an else statement, but during a 
>> pre-review of the patch I got feedback to change it to CHECK_NULL and 
>> get rid of the else statement. :)
>>
>> Here's a new webrev with nullHandle and the else statement:
>> http://cr.openjdk.java.net/~stefank/8065634/webrev.02
>>
>> Thanks,
>> StefanK
>>
>> On 2014-12-03 14:31, harold seigel wrote:
>>> Hi Stefan,
>>>
>>> The change looks good but I have a couple of questions.
>>>
>>> 1. Why does the call to create_combined_annotations(), in 
>>> parseClassFile(), use CHECK_NULL when other calls use 
>>> CHECK_(nullHandle) ?
>>>
>>> 4021     ClassAnnotationCollector parsed_annotations;
>>> 4022     parse_classfile_attributes(&parsed_annotations, 
>>> CHECK_(nullHandle));
>>> 4023
>>> 4024     // Finalize the Annotations metadata object,
>>> 4025     // now that all annotation arrays have been created.
>>> 4026     create_combined_annotations(CHECK_NULL);
>>> 4027
>>> 4028     // Make sure this is the end of class file stream
>>> 4029     guarantee_property(cfs->at_eos(), "Extra bytes at the end 
>>> of class file %s", CHECK_(nullHandle));
>>>
>>>
>>> 2. In ~ClassFileParser(), does MetadataFactory::free_array() and 
>>> Annotations::free_contents() need to be called if the *_annotation 
>>> fields are NULL?
>>>
>>>
>>> Thanks, Harold
>>>
>>> On 12/3/2014 9:21 AM, Stefan Karlsson wrote:
>>>> Hi all,
>>>>
>>>> Please, review this patch to fix an issue where the GC encounters 
>>>> an InstanceKlass before it has come far enough in the class loading 
>>>> process.
>>>>
>>>> Some background to the fix:
>>>>
>>>> When the JVM loads classes it has to keep track of the allocated 
>>>> Metadata, and in the event of an exception deallocate the Metadata. 
>>>> The ClassFileParser saves the Metadata pointers so that it knows 
>>>> what needs to be deallocated. When the class loading has come far 
>>>> enough there's a point were the GC can take over the ownership of 
>>>> the Metadata and do deallocation of the both the InstanceKlass and 
>>>> the Metadata, if needed. At that point the Metadata pointers in the 
>>>> ClassFileParser are cleared and transfered over to the InstanceKlass.
>>>>
>>>> Most Metadata allocations happen before the InstanceKlass is 
>>>> allocated, but the Annotations are allocated after the 
>>>> InstanceKlass but before the transferal and clearing of the 
>>>> Metadata pointers in the ClassFileParser. If the GC stops when 
>>>> allocating the Annotations, it will likely find this InstanceKlass 
>>>> and assume that the Metadata are correctly setup. This is exactly 
>>>> what's happening in the bug report. The GC finds that the _methods 
>>>> array, unexpectedly, points to NULL.
>>>>
>>>> The proposed solution to this problem is to allocate the 
>>>> Annotations before the InstanceKlass is allocated.
>>>>
>>>> http://cr.openjdk.java.net/~stefank/8065634/webrev.01
>>>> https://bugs.openjdk.java.net/browse/JDK-8065634
>>>>
>>>> Testing:
>>>> JPRT, parallel_class_loading testlist, Aurora adhoc run
>>>>
>>>> Thanks,
>>>> StefanK
>>>
>>
>