RFR: 8267842: SIGSEGV in get_current_contended_monitor [v2]

[David Holmes]

On Thu, 27 May 2021 16:56:25 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> We need a fix for crashes in get_current_contended_monitor due to concurrent modification of memory locations which are not declared volatile. See bug for details.
>
> Martin Doerr has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add comments as suggested by Dan.

Hi Martin,

I'm with @stefank. This special case is a race condition and the solution for that is Atomic::load/store. Given Atomic::load/store don't actually need to do anything in practice (other than act as marker of a race) I don't have any qualms about using them all the time.

Seperately, I'm unclear why we allow this race to exist. I thought we took snapshots when threads were known to be safe and stable. But that is a separate issue.

Cheers,
David

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PR: https://git.openjdk.java.net/jdk/pull/4224