RFR: 8321075: RISC-V: UseSystemMemoryBarrier lacking proper OS support [v2]

[Fei Yang]

On Mon, 19 Feb 2024 09:01:20 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

>> Hi, please consider.
>> 
>> RV port was pickup into mainline Linux 4.4.
>> The same version also made membar private expedited mandatory, but this was missed in RV port.
>> This means to we need to check kernel version in runtime to figure out if it's usable.
>> 
>> Kernel fix is here:
>> https://git.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git/commit/?h=for-next&id=0420af54c2c2b7b3abbd986a41aded7cab0137ef
>
> Robbin Ehn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fixed version check

Hi, Just wondering if there is a plan for the kernel fix to be backported to some longterm kernel versions like 6.6, 5.10 or even 4.19? UseSystemMemoryBarrier won't be usable with this change when we are running on top of those older kernels if that happens.

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PR Review: https://git.openjdk.org/jdk/pull/17889#pullrequestreview-1887949057