[External] : Re: A noob question about weird sequence of `*synchronization entry` in a C2 compiled code

[Jaroslav Bachorík]

Hi Tobias,

Thanks for fixing this subtle and annoying bug. Looking forward to having
the fix accepted so we can start backporting it.

Cheers,

Jaroslav

On Wed 1. 3. 2023 at 16:17, Tobias Hartmann <tobias.hartmann at oracle.com>
wrote:

> Hi Jaroslav,
>
> I finally got the time to investigate this properly and found the root
> cause. The fix is out for
> review: https://github.com/openjdk/jdk/pull/12806
>
> Thanks again for reporting this!
>
> Best regards,
> Tobias
>
>
> On 07.02.22 23:20, dean.long at oracle.com wrote:
> > It turns out the problem with DebugNonSafepoints is a known issue.  See
> > https://bugs.openjdk.java.net/browse/JDK-8201516.
> >
> > dl
> >
> > On 2/7/22 7:58 AM, Jaroslav Bachorík wrote:
> >> Hi Dean,
> >>
> >> The first thing I want to mention is that I isolated  this behaviour
> >> to be triggered by `-XX:DebugNonSafepoints` JVM arg. When this option
> >> is not specified I don't see the pattern at all.
> >>
> >> I have extracted a self-contained (almost) reproducer - it is not a
> >> single class, unfortunately, but building and running it is as simple
> >> as executing the attached `./run.sh`
> >> The reproducer has a weak point, though - I am not able to get the
> >> `*synchronization entry` pattern manifesting at the same locations.
> >> Therefore it is more of PoC than a full test case - it requires going
> >> to the assembly print out and searching for `*synchronization entry`
> >> manually.
> >>
> >> The project can be found here -
> >>
> https://urldefense.com/v3/__https://drive.google.com/file/d/1Z6rX4NpvNpctVA3AuYfaG0Qxjd4KjrED/view?usp=sharing__;!!ACWV5N9M2RV99hQ!f9PhKRCRHuSdH__32-XrLtTdu0RoQCQz8wJGjvsqF83SjHg4R2_vAcUJOJFYqd4$
> >> It is a zipped gradle java project and the only thing it requires is a
> >> working Java env.
> >>
> >> Thanks!
> >>
> >> -JB-
> >>
> >> On Sun, Feb 6, 2022 at 6:45 AM <dean.long at oracle.com> wrote:
> >>>
> >>> On 2/5/22 12:58 PM, Jaroslav Bachorík wrote:
> >>>> Is this the hard limitation of what is possible to do with the debug
> >>>> data at this level of optimization? Are some boundaries irreversibly
> >>>> lost here?
> >>>
> >>> It's quite likely you've discovered a bug that can be fixed.  If you
> >>> could narrow it down to a self-contained test case, that would really
> help.
> >>>
> >>> dl
>
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