[8u] RFR 8233197: Invert JvmtiExport::post_vm_initialized() and Jfr:on_vm_start() start-up order for correct option parsing

[Andrew Hughes]

On 08/06/2020 17:41, Jaroslav Bachorík wrote:
> Hi Andrew,
> 


snip...

>>
>> 1. How prolific is such usage of JFR?
> 
> I guess not much since till recently each attempt would have resulted
> in segfault.
> But in general I would say that any APM/Profiler based on JFR would be
> happy not to run a special delay code to prevent segfaults.
> 

Ok, I guess that applies to JFR in later OpenJDK versions (i.e. those in
releases) as well as 8u.

>>
>> 2. What are the risks of including this patch?
> 
> In general, changing the initialization order for java.lang.Class
> could cause problems for a code that would operate with assumption of
> the java.lang.Class not being initialized very early on in the JVM
> startup. This sounds pretty unlikely, though - eg tier1, tier2 and jfr
> tests are still passing after adding this change
> 

It's still pretty worrying to be altering this in a very stable release
(though, adding JFR itself is worrying as well)

I'll let Andrew Haley make the final call on whether he is happy to
allow this or not.

> 
>>
>> 3. Do we now have a final version of this patch, with test?
> 
> Yes. The webrev.04 version is the final one.
> 
> 
>>
>> 4. Was a bug filed for the additional test?
> 
> https://bugs.openjdk.java.net/browse/JDK-8246703
> 

Thanks for this follow-up.

Cheers,
-- 
Andrew :)

Senior Free Java Software Engineer
Red Hat, Inc. (http://www.redhat.com)

PGP Key: ed25519/0xCFDA0F9B35964222 (hkp://keys.gnupg.net)
Fingerprint = 5132 579D D154 0ED2 3E04  C5A0 CFDA 0F9B 3596 4222