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8274004: Change 'nonleaf' rank name #5845

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8274004: Change 'nonleaf' rank name #5845

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coleenp
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@coleenp coleenp commented Oct 6, 2021

Also fixes: 8273956: Add checking for rank values

This change does 3 things. I could separate them but this has all been tested together and most of the change is mechanical. The first is a simple rename of nonleaf => safepoint. The second change is to add the enum class Rank which only allows subtraction from a base rank, and some additional type checking so that rank arithmetic doesn't overlap with a different rank. Ie if you say nosafepoint-n, that doesn't overlap with oopstorage. The third change is to remove the _safepoint_check_always/never flag. That is now intrinsic in the ranking, as all nosafepoint ranks are lower than all safepoint ranks.

Future changes could add rank names in the middle of nosafepoint and safepoint, like handshake. As of now, the rank subtractions are not unmanageable. There are actually not many nested Mutex.

This is the last of the planned subtasks for Mutex ranking cleanup. If you have other ideas or suggestions, please let me know.

Tested with tier1-8 at one point in time and just retested with tier1-6.


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8273956: Add checking for rank values
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@bridgekeeper bridgekeeper bot commented Oct 6, 2021

👋 Welcome back coleenp! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

@openjdk openjdk bot added the rfr label Oct 6, 2021
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@openjdk openjdk bot commented Oct 6, 2021

@coleenp The following labels will be automatically applied to this pull request:

  • hotspot
  • serviceability
  • shenandoah

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

@openjdk openjdk bot added serviceability hotspot shenandoah labels Oct 6, 2021
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@mlbridge mlbridge bot commented Oct 6, 2021

Webrevs

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@dcubed-ojdk dcubed-ojdk commented Oct 6, 2021

The PR description mentions:
8273956: Add checking for rank values
but the PR synopsis is:
8274004: Change 'nonleaf' rank name

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@mlbridge mlbridge bot commented Oct 6, 2021

Mailing list message from coleen.phillimore at oracle.com on hotspot-dev:

On 10/6/21 7:45 PM, Daniel D.Daugherty wrote:

On Wed, 6 Oct 2021 23:27:17 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

8273956: Add checking for rank values

This change does 3 things. I could separate them but this has all been tested together and most of the change is mechanical. The first is a simple rename of nonleaf => safepoint. The second change is to add the enum class Rank which only allows subtraction from a base rank, and some additional type checking so that rank arithmetic doesn't overlap with a different rank. Ie if you say nosafepoint-n, that doesn't overlap with oopstorage. The third change is to remove the _safepoint_check_always/never flag. That is now intrinsic in the ranking, as all nosafepoint ranks are lower than all safepoint ranks.

Future changes could add rank names in the middle of nosafepoint and safepoint, like handshake. As of now, the rank subtractions isn't unmanageable. There are actually not many nested Mutex.

This is the last of the planned subtasks for Mutex ranking cleanup. If you have other ideas or suggestions, please let me know.

Tested with tier1-8 at one point in time and just retested with tier1-6.
The PR description mentions:
`8273956: Add checking for rank values`
but the PR synopsis is:
`8274004: Change 'nonleaf' rank name`

It's actually both.? But I should close the 8273956 as a duplicate of
the first and remove that line in the description.
thanks,
Coleen

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@dcubed-ojdk dcubed-ojdk commented Oct 6, 2021

Just do

/issue JDK-8274004
/issue JDK-8273956

and this PR will cover both.

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@dcubed-ojdk Only the author (@coleenp) is allowed to issue the /issue command.

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@openjdk openjdk bot commented Oct 6, 2021

@dcubed-ojdk Only the author (@coleenp) is allowed to issue the /issue command.

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@coleenp coleenp commented Oct 7, 2021

/issue JDK-8274004
/issue JDK-8273956

Thank you @dcubed-ojdk!

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@openjdk openjdk bot commented Oct 7, 2021

@coleenp This issue is referenced in the PR title - it will now be updated.

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@openjdk openjdk bot commented Oct 7, 2021

@coleenp
Adding additional issue to issue list: 8273956: Add checking for rank values.

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@dholmes-ora dholmes-ora left a comment

Hi Coleen,

Overall this looks good! But shouldn't the test:

test/hotspot/gtest/runtime/test_safepoint_locks.cpp

be replaced by one that checks we lock with/without a safepoint check for a safepoint/nonsafepoint lock respectively? (Or does that test already exist elsewhere?).

Also should there not be a gtest to verify your Rank overlap checking?

Thanks,
David

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@pchilano pchilano left a comment

LGTM!

Thanks,
Patricio

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@coleenp coleenp commented Oct 7, 2021

Thanks for the review @pchilano and offline discussion about check_for_overlap.

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@dholmes-ora dholmes-ora left a comment

Hi Coleen,

A couple of comments on tests, but otherwise okay.

Thanks,
David

monitor_rank_broken->lock_without_safepoint_check();
monitor_rank_broken->unlock();
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This is dead code right - the assertion failure will stop us getting here.

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@coleenp coleenp Oct 8, 2021

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Yes, it is dead code. I'll remove it and retest to make sure nothing surprising happens.

monitor_rank_broken->lock_without_safepoint_check();
monitor_rank_broken->unlock();
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Ditto - dead code

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@coleenp coleenp Oct 8, 2021

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removed.

JavaThread* THREAD = JavaThread::current();
ThreadInVMfromNative invm(THREAD);

Monitor* monitor_rank_broken = new Monitor(Mutex::safepoint-1, "monitor_rank_broken");
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This rank is not actually broken is it - otherwise we won't get to the next line.

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@coleenp coleenp Oct 8, 2021

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right. It's not broken. I'll rename it to 'monitor_rank_ok'.

monitor_rank_also_broken->lock_without_safepoint_check();
monitor_rank_also_broken->unlock();
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@dholmes-ora dholmes-ora Oct 8, 2021

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Dead code

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@coleenp coleenp Oct 8, 2021

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removed.

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

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

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

8274004: Change 'nonleaf' rank name
8273956: Add checking for rank values

Reviewed-by: dholmes, pchilanomate

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 23 new commits pushed to the master branch:

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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@coleenp coleenp left a comment

I removed the dead test code and retested.

monitor_rank_broken->lock_without_safepoint_check();
monitor_rank_broken->unlock();
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@coleenp coleenp Oct 8, 2021

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Yes, it is dead code. I'll remove it and retest to make sure nothing surprising happens.

monitor_rank_broken->lock_without_safepoint_check();
monitor_rank_broken->unlock();
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@coleenp coleenp Oct 8, 2021

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removed.

JavaThread* THREAD = JavaThread::current();
ThreadInVMfromNative invm(THREAD);

Monitor* monitor_rank_broken = new Monitor(Mutex::safepoint-1, "monitor_rank_broken");
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@coleenp coleenp Oct 8, 2021

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right. It's not broken. I'll rename it to 'monitor_rank_ok'.

monitor_rank_also_broken->lock_without_safepoint_check();
monitor_rank_also_broken->unlock();
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@coleenp coleenp Oct 8, 2021

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removed.

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@coleenp coleenp commented Oct 8, 2021

Thanks for the code review David, and all the discussions leading to this change.

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@coleenp coleenp commented Oct 8, 2021

/integrate

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@openjdk openjdk bot commented Oct 8, 2021

Going to push as commit 6364719.
Since your change was applied there have been 23 commits pushed to the master branch:

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot closed this Oct 8, 2021
@openjdk openjdk bot added integrated and removed ready rfr labels Oct 8, 2021
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@openjdk openjdk bot commented Oct 8, 2021

@coleenp Pushed as commit 6364719.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

@coleenp coleenp deleted the rank branch Oct 8, 2021
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