[crac] RFR: RFC: -XX:CPUFeatures=0xnumber for CPU migration [v24]

[Anton Kozlov]

On Thu, 1 Jun 2023 13:44:36 GMT, Jan Kratochvil <jkratochvil at openjdk.org> wrote:

>> It was needed for some previous variant of the patch and it is a leftover. Removed. Sorry for not self-reviewing this version of my patch.
>
> It is in fact needed: https://github.com/openjdk/crac/blob/08c2c0f2b140b1011fec39a1a83037df8e59577d/src/hotspot/os_cpu/linux_x86/os_linux_x86.cpp#L217
> During CRaC restore there is somehow no Java thread created yet that time. I do not understand this much so I left it there as working but maybe some Java thread should be initialized earlier?

Sorry, I've missed the comment in the code. Looks OK.

Since verify_cpu_compatibility is called from VMThread, which is not JavaThreads, the thread is not passed from the caller.

https://github.com/openjdk/crac/blob/08c2c0f2b140b1011fec39a1a83037df8e59577d/src/hotspot/os/posix/signals_posix.cpp#L627

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PR Review Comment: https://git.openjdk.org/crac/pull/41#discussion_r1222925825