8359105: RISC-V: No need for acquire fence in safepoint poll during JNI calls

[Anjian-Wen]

Acquire fence removal in safepoint_poll

At least in jdk11, when comes to safepoint::end, it will invoke SafepointMechanism::disarm_local_poll to change the polling_word_offset, which may cause a race when thread come to visit polling_word_offset in native_trans state, so we used to use acquire fence.

Since the disarm_local_poll has been removed from SafepointSynchronize::end, Thread disarm itself in
JavaThread::check_special_condition_for_native_trans when trans from native. it seems that there is no need for acquire fence in safepoint_poll.

[0] #20420

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Issue

• JDK-8359105: RISC-V: No need for acquire fence in safepoint poll during JNI calls (Enhancement - P4)

Reviewers

• Robbin Ehn (@robehn - Reviewer)
• Fei Yang (@RealFYang - Reviewer)
• Feilong Jiang (@feilongjiang - Committer)

Reviewing

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@Anjian-Wen This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8359105: RISC-V: No need for acquire fence in safepoint poll during JNI calls

Reviewed-by: rehn, fyang, fjiang

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At the time when this comment was updated there had been 67 new commits pushed to the master branch:

• 26848a7: 8358804: Improve the API Note of BigDecimal.valueOf(double)
• 0e725c6: 8354447: Missing test for retroactive @SuppressWarnings("dangling-doc-comments") behavior
• b3f5608: 8358094: Test vmTestbase/nsk/jvmti/AttachOnDemand/attach045/TestDescription.java still times out after JDK-8357282
• ... and 64 more: https://git.openjdk.org/jdk/compare/ca7b885873712a5ae503cb82c915d709034a69f7...master

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[Anjian-Wen]

/issue JDK-8359105

[openjdk]

@Anjian-Wen The primary solved issue for a PR is set through the PR title. Since the current title does not contain an issue reference, it will now be updated.

[mlbridge]

Webrevs

• 01: Full - Incremental (47065b4a)
• 00: Full (5ca62af4)

[Anjian-Wen]

@robehn Hi, Can you help to review the patch?

[robehn]

Hey, sure.

The description says "backport of", as you are changing master I think that description is wrong.

The downcallLinker_riscv.cpp is the same case as the native transition.
So I don't see why you would keep that acquire ?

AFIACT no one should use acquire, thus this should then mean that we can remove "bool acquire" argument from safepoint_poll().

That arm still have acquire in their downlinker seems like an oversight?
8337657 only have one reviewer, I think it should have been cought there.
(please note https://wiki.openjdk.org/display/HotSpot/Pushing+a+HotSpot+change, two reviewers required)
@dchuyko can you open a new issue and look at the acquire in downcall linker for aarch64 ?

Thanks, Robbin

[dchuyko]

@dchuyko can you open a new issue and look at the acquire in downcall linker for aarch64 ?

Thanks for the reminder, created JDK-8359252. It was intentional to limit the scope of the original change to JNI (due the amount of testing and usages).

[Anjian-Wen]

Thanks for your review!! I have changed the description.
About the safepoint_poll, I think it makes sence that there is no need to keep "bool acquire" argument when we change the last 'true' in downcallLinker_riscv.cpp, and I have updated the patch.

Hey, sure.

The description says "backport of", as you are changing master I think that description is wrong.

The downcallLinker_riscv.cpp is the same case as the native transition. So I don't see why you would keep that acquire ?

AFIACT no one should use acquire, thus this should then mean that we can remove "bool acquire" argument from safepoint_poll().

That arm still have acquire in their downlinker seems like an oversight? 8337657 only have one reviewer, I think it should have been cought there. (please note https://wiki.openjdk.org/display/HotSpot/Pushing+a+HotSpot+change, two reviewers required) @dchuyko can you open a new issue and look at the acquire in downcall linker for aarch64 ?

Thanks, Robbin

[robehn]

@dchuyko can you open a new issue and look at the acquire in downcall linker for aarch64 ?

Thanks for the reminder, created JDK-8359252. It was intentional to limit the scope of the original change to JNI (due the amount of testing and usages).

Thank you!

[robehn]

Thanks, looks good!

[RealFYang]

LGTM. FYI: I see another pending PR (#25211) which handles the rest for aarch64.

[feilongjiang]

Looks fine. Thanks!

[Anjian-Wen]

/integrate

[openjdk]

@Anjian-Wen
Your change (at version 47065b4) is now ready to be sponsored by a Committer.

[Anjian-Wen]

@robehn @feilongjiang @RealFYang Thanks for your review and approve !

[feilongjiang]

/sponsor

[openjdk]

Going to push as commit 1a01839.
Since your change was applied there have been 67 commits pushed to the master branch:

• 26848a7: 8358804: Improve the API Note of BigDecimal.valueOf(double)
• 0e725c6: 8354447: Missing test for retroactive @SuppressWarnings("dangling-doc-comments") behavior
• b3f5608: 8358094: Test vmTestbase/nsk/jvmti/AttachOnDemand/attach045/TestDescription.java still times out after JDK-8357282
• ... and 64 more: https://git.openjdk.org/jdk/compare/ca7b885873712a5ae503cb82c915d709034a69f7...master

Your commit was automatically rebased without conflicts.

[openjdk]

@feilongjiang @Anjian-Wen Pushed as commit 1a01839.

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