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

[Robbin Ehn]

> 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

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17889/files
  - new: https://git.openjdk.org/jdk/pull/17889/files/9975040a..819c891c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17889&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17889&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/17889.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17889/head:pull/17889

PR: https://git.openjdk.org/jdk/pull/17889