RFR: 8321075: RISC-V: UseSystemMemoryBarrier lacking proper OS support

[Yadong Wang]

On Fri, 16 Feb 2024 13:01:20 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

src/hotspot/os/linux/systemMemoryBarrier_linux.cpp line 70:

> 68:   long major, minor;
> 69:   os::Linux::kernel_version(&major, &minor);
> 70:   if (!(major >= 6 && minor >= 9)) {

Is there something wrong with this conditional expression? What happens if it's 7.0?

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PR Review Comment: https://git.openjdk.org/jdk/pull/17889#discussion_r1493624787