RFR: 8315373: Change VirtualThread to unmount after freezing, re-mount before thawing [v2]

[Alan Bateman]

On Fri, 1 Sep 2023 11:32:45 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

>> Thanks. One other thing that I see when more testing with generational ZGC is that ZPageAllocator::alloc_page will record an event and this can happen during a mount transition. So I think JfrStackTrace::record also needs to test if the current thread is a virtual thread without a continuation mounted.
>
> That is not good. Such a check would be attributed to all event sites, making them all slower.

Markus has suggested, and provided the change, to handle the synchronous case in JfrStackTrace. The testing is looking good with the combined changes.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/15492#discussion_r1314643730