RFR: 8310239: Add missing cross modifying fence in nmethod entry barriers [v2]

[Andrew Haley]

On Wed, 9 Aug 2023 02:00:57 GMT, Dean Long <dlong at openjdk.org> wrote:

> I was thinking the issue Erik was worried about is patching of nmethod code as data at safepoints. I seem to recall there are certain kinds of stubs that need to patch more than one word, so it is done at a safepoint. I see code in SafepointMechanism::update_poll_values() that calls OrderAccess::cross_modify_fence() in certain cases, so maybe that's enough?

It certainly should be.

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PR Comment: https://git.openjdk.org/jdk/pull/14543#issuecomment-1671762440