Proposal: Allowing selective pushes to hotspot without jprt

[Mikael Vidstedt]

All,

Made up primarily of low level C++ code, the Hotspot codebase is highly 
platform dependent and also tightly coupled with the tool chains on the 
various platforms. Each platform/tool chain combination has its set of 
special quirks, and code must be implemented in a way such that it only 
relies on the common subset of syntax and functionality across all these 
combinations. History has taught us that even simple changes can have 
surprising results when compiled with different compilers.

For more than a decade the Hotspot team has ensured a minimum quality 
level by requiring all pushes to be done through a build and test system 
(jprt) which guarantees that the code resulting from applying a set of 
changes builds on a set of core platforms and that a set of core tests 
pass. Only if all the builds and tests pass will the changes actually be 
pushed to the target repository.

We believe that testing like the above, in combination with later stages 
of testing, is vital to ensuring that the quality level of the Hotspot 
code remains high and that developers do not run into situations where 
the latest version has build errors on some platforms.

Recently the AIX/PPC port was added to the set of OpenJDK platforms. 
 From a Hotspot perspective this new platform added a set of AIX/PPC 
specific files including some platform specific changes to shared code. 
The AIX/PPC platform is not tested by Oracle as part of Hotspot push 
jobs. The same thing applies for the shark and zero versions of Hotspot.

While Hotspot developers remain committed to making sure changes are 
developed in a way such that the quality level remains high across all 
platforms and variants, because of the above mentioned complexities it 
is inevitable that from time to time changes will be made which 
introduce issues on specific platforms or tool chains not part of the 
core testing.

To allow these issues to be resolved more quickly I would like to 
propose a relaxation in the requirements on how changes to Hotspot are 
pushed. Specifically I would like to allow for direct pushes to the 
hotspot/ repository of files specific to the following ports/variants/tools:

* AIX
* PPC
* Shark
* Zero

Today this translates into the following files:

- src/cpu/ppc/**
- src/cpu/zero/**
- src/os/aix/**
- src/os_cpu/aix_ppc/**
- src/os_cpu/bsd_zero/**
- src/os_cpu/linux_ppc/**
- src/os_cpu/linux_zero/**

Note that all changes are still required to go through the normal 
development and review cycle; the proposed relaxation only applies to 
how the changes are pushed.

If at code review time a change is for some reason deemed to be risky 
and/or otherwise have impact on shared files the reviewer may request 
that the change to go through the regular push testing. For changes only 
touching the above set of files this expected to be rare.

Please let me know what you think.

Cheers,
Mikael