RFR: 8275800: Redefinition leaks MethodData::_extra_data_lock [v2]

[David Holmes]

On Mon, 25 Oct 2021 22:17:33 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> // Can't release the constant pool here because the constant pool can be
>>      // deallocated separately from the InstanceKlass for default methods and
>>      // redefine classes.
>> 
>> Because of this comment.  We have two ways that we can get to ConstantPool::deallocate_contents.  We don't have two ways to get to the Method::deallocate_contents.
>> 
>> The deallocate list contains unloaded/unattached Methods (from the relocator for jsr/ret), scratch classes from redefinition, fully formed constant pools from default methods, or fully formed InstanceKlass from classfile parsing errors or class definition errors.
>> 
>> Only the constant pool case should be separated out in deallocate_contents, which is why it's excluded.
>
> Is the suggestion to have a default parameter to free CHEAP structures that's false for deallocate_contents?
> I'm not really sure it's an improvement because I have to have an extra parameter to Klass::release_C_heap_structures that's unused.

That is one option but I was thinking perhaps remove `constants()->release_C_heap_structures()` from `instanceKlass::release_C_heap_structures()` and have the callers that should remove the CP call `ik->constants()->release_C_heap_structures()` directly?
Or perhaps just change this comment:


 // Release C heap allocated data that this points to, which includes
  // reference counting symbol names.
  release_C_heap_structures_internal();


to 

` // reference counting symbol names, but excludes the constant pool.`

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PR: https://git.openjdk.java.net/jdk/pull/6105