RFR: 8347422: Crash during safepoint handler execution with -XX:+UseAPX

[Daniel Lundén]

On Mon, 13 Jan 2025 15:16:55 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>>> Technically, randomizing allocation sequence from the same register class is not very useful
>> 
>> It's definitely useful to catch bugs where silent register corruption is never detected because that exact register is not used anywhere else. Or for cases where a specific register is not saved although it should be but we don't notice because that register is not used anywhere else. And we had quite a few bugs like this in the past.
>> 
>> Wouldn't such a random register selection also randomly prioritize EGPRs and therefore do the same thing that you did manually? And if not, doesn't that mean that we should definitely add such a stress flag?
>> 
>>> Yes, but with -XX:+SafepointALot crash hit early.
>> 
>> Okay, good then.
>
>> > Technically, randomizing allocation sequence from the same register class is not very useful
>> 
>> It's definitely useful to catch bugs where silent register corruption is never detected because that exact register is not used anywhere else. Or for cases where a specific register is not saved although it should be but we don't notice because that register is not used anywhere else. And we had quite a few bugs like this in the past.
>> 
> 
> I see, Thanks @TobiHartmann, scope of JDK- 8343294 can be extended to cover EGPRs to catch such silent bugs, to strees validating all JVM components I am taking a brute force approach to begin with. You can assign JDK-8343294 to me if Daniel is not active on that.
> 
>> Wouldn't such a random register selection also randomly prioritize EGPRs and therefore do the same thing that you did manually? And if not, doesn't that mean that we should definitely add such a stress flag?
>> 
>> > Yes, but with -XX:+SafepointALot crash hit early.
>> 
>> Okay, good then.
> 
> Let me know if this looks ok for now.

Hi @jatin-bhateja. Feel free to have a look at JDK-8343294 (and assign yourself). Please ping me for the review when the changeset is ready!

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PR Comment: https://git.openjdk.org/jdk/pull/23035#issuecomment-2587445078