Integrated: 8302760: Improve liveness/remembered set verification for G1

[Thomas Schatzl]

On Mon, 20 Feb 2023 12:48:25 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   can I have reviews for this refactoring/cleanup of the liveness/remembered set verification code for G1?
> 
> Here is an overview of the changes
>  - previously liveness and remembered set verification could be done separately. Thismade the code a bit more complicated than necessary; now that remembered set verification always follows liveness verification, the code can assume that and do some minor cleanup. I kept the remembered verification a separate closure (`VerifyRemSetClosure`) because the additional boiler plate code is negligible compared to the other duplication that would have been needed around failure count tracking.
>  - factored out liveness and remembered set verification from `HeapRegion::verify`, and heavily cleaned up the resulting `HeapRegion::verify_liveness_and_remembered_set`. This includes some removal of code duplication wrt to the failure count tracking.
> - factored out a special `G1VerificationClosure::is_oop_safe` method that adds more checking of the `Klass`; I hesitated to put this into `Universe::is_oop` as this is much more extensive checking (and I wanted implicit error reporting :))
> - CollectedHeap::is_oop() should use `klass_raw` because otherwise it will immediately assert on oops with garbage Klass values (the new code will just return `false` as expected). 
> - some special `oopDesc::print_name_on()` which does not crash on bad oops, similar to existing related debugging helpers.
> 
> Thanks,
>   Thomas

This pull request has now been integrated.

Changeset: 5d7e7e28
Author:    Thomas Schatzl <tschatzl at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/5d7e7e28b1d96b3bf387104f6c98da022aed76d5
Stats:     340 lines in 9 files changed: 120 ins; 151 del; 69 mod

8302760: Improve liveness/remembered set verification for G1

Reviewed-by: kbarrett, iwalulya

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PR: https://git.openjdk.org/jdk/pull/12660