RFR: 8306767: Concurrent repacking of extra data in MethodData is potentially unsafe [v18]

[Roland Westrelin]

On Wed, 17 Jan 2024 08:33:14 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> Emanuel Peter has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   NoSafepointMutexLocker
>
> Looks good to me. Thanks for making the changes. Do we want to file a bug to refactor the code?

> @rwestrel thanks for the review! I pushed a comment improvement.
> 
> What kind of refactoring are you thinking about? Just to remove the `MutexUnlocker` occurrence, or something bigger?

I was thinking maybe something along the lines of what Tom suggested: " I think the API would need to make a stronger split between preallocated records and records which might come from the extra data section. "
It doesn't seem right that the API can return a pointer to something that's not safe to access unless we own a lock too.

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PR Comment: https://git.openjdk.org/jdk/pull/16840#issuecomment-1896005676