RFR: 8292591: Experimentally add back barrier-less Java thread transitions [v5]

[Robbin Ehn]

On Fri, 9 Sep 2022 16:25:54 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

>> Robbin Ehn has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fixed ws
>
> src/hotspot/os/linux/systemMemoryBarrier_linux.cpp line 51:
> 
>> 49:   MEMBARRIER_CMD_PRIVATE_EXPEDITED          = (1 << 3),
>> 50:   MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED = (1 << 4),
>> 51: };
> 
> Does there need to be some form of "#ifndef XXX" ... "#endif" bracketing
> for when we eventually reach systems running kernel 4.14?

The plan is when the build system fully supports AC_CHECK_DECL, auto conf will check this for and set a define.

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PR: https://git.openjdk.org/jdk/pull/10123