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

[dean.long at oracle.com]

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