[RFC] Proposal to backport JEP 386 (Alpine Linux Port) to 11u

Thu Feb 24 12:56:43 UTC 2022

Hi Thomas,

see inline:

On 23/02/2022 21:18, Thomas Stüfe wrote:
> Hi Alexei,
>
> I think this makes sense and is probably less risky than backporting
> JEP 388 and JEP 391. Thanks for doing the work, this looks well
> prepared for review already.
>
> I have some questions, which had not been immediately clear from the
> mail. I may be just slow.
>
> - Did you have to make 11u specific changes to the individual
> backports? If yes, what and why?
Speaking of product code changes, all changes that had to be done for
11u are cosmetic, it's mostly lines layout that had to be taken care of.
8252248 is slightly different because of Solaris support in 11u, but
these changes are under #ifdefs in libnio/ch/NativeThread.c.
> - are there changes to the glibc variant in 11u, and if yes, why? In
> other words, will anything change for the existing platforms? Because
> theoretically, nothing should, right? I see the change to isnan, is
> that motivated to just applying the upstream patch without change, or
> was there a deeper reason?

Yes, there are changes to glibc variant in 11u which are limited to 100
lines of code. Most of the work done for Alpine Linux support was
actually cleanup to linux code. My take with the 11u backport is to keep
it simple and in line with what was contributed to 16 to simplify
maintenance. Let me break down the changes en large so you can also do
the risk assessment

- 8245938 removes dead code (also dead in 11u)
- 8252248 glibc-private  __SIGRTMAX is replaced with public standard
SIGRTMAX
- 8252250 isnan change analysis can be found in
https://bugs.openjdk.java.net/browse/JDK-8178689 comments
- 8247589 First, this change uses libnuma2 if available with fallback to
libnuma if libnuma2 is not found. Second, mmap and mprotect are called
at VM initialization to enable JDK to work on systems with PaX
grsecurity. No new API is used in terms of libc/glibc compatibility
level. Both changes are not specific to Alpine (aside from the fact that
Alpine enables it by default).

Thanks,

-Aleksei

>
> Thank you!
>
> Thomas
>
>
> On Thu, Feb 17, 2022 at 3:12 PM Aleksei Voitylov
> <aleksei.voitylov at bell-sw.com <mailto:aleksei.voitylov at bell-sw.com>>
> wrote:
>
>     Hi,
>
>     Following recent backports of JEP 388 (Windows/AArch64 Port) and
>     JEP 391
>     (macOS/AArch64 Port), I’d like to propose a backport of JEP 386
>     (Alpine
>     Linux Port) [1] to OpenJDK 11u. Support for this port was baked in the
>     Portola project and integrated into OpenJDK 16.
>
>     Motivation for 11u backport: the importance of this platform is
>     explained by wide adoption of Alpine Linux in container environments
>     [2]. Several OpenJDK vendors (Liberica, Corretto, Zulu) include
>     patches
>     that enable Alpine/MUSL for 11u and 8u for quite some time,
>     without any
>     issues. Others (MS) have recently added it. In our case the user
>     demand
>     for Alpine/musl support for both 11u and 8u was at least as strong as
>     Mac/AArch64 and Windows/AArch64, I’d also like to hear if other
>     OpenJDK
>     vendors share our view of the importance of this platform in 11u.
>
>     The set of JBS issues required to be backported for Alpine/MUSL
>     support
>     in 11u is:
>
>     JDK-8217340 Compilation failed: tools/launcher/Test7029048.java
>     -    Test-only fix
>     JDK-8247592 refactor test/jdk/tools/launcher/Test7029048.java
>     -    Test-only fix
>     JDK-8245938 Remove unused print_stack(void) method from XToolkit.c
>     -    Code fix, removal of dead code, applies cleanly
>     JDK-8252248 __SIGRTMAX is not declared in musl libc
>     -    Code fix
>     JDK-8252250 isnanf is obsolete
>     -    Code fix, substitutes isnanf with isnan which was proven to be ok
>     at least since GLIBC 2.8/GCC 4.6 on Linux and any reasonable LLVM
>     version – see the discussion in JDK-8178689 for further details.
>     JDK-8247589 Implementation of Alpine Linux/x64 Port
>     -    The actual build and code changes that tidy up code for MUSL
>     JDK-8247591 Document Alpine Linux build steps in OpenJDK build guide
>     -    Docs only fix
>
>     All patches combined: +480 lines, -146 lines.
>     All source code changes: +133 lines, -43 lines.
>
>     For risk assessment and preliminary examination of the 11u
>     maintainers,
>     the full patchset can be observed in [3], separate 11u backports
>     can be
>     found in [4]. I plan to submit the actual PRs for individual backports
>     one by one unless I hear reasonable concerns from 11u maintainers
>     on the
>     proposed changes.
>
>     The patchset passes full JCK+jtreg set without any regressions to
>     other
>     platforms (Windows, Linux, Mac, Solaris), including non-Intel where
>     applicable. During integration of JEP 386 SAP kindly verified that
>     these
>     changes do not break AIX/XLC.
>
>     On the maintenance side, BellSoft will be happy to support this
>     platform
>     in 11u. But I’ll equally happily share the burden with other OpenJDK
>     vendors that currently support Alpine/MUSL.
>
>     Thanks,
>     -Aleksei
>
>     [1] https://openjdk.java.net/jeps/386
>     [2] https://hub.docker.com/_/alpine
>     [3]
>     https://github.com/voitylov/jdk11u-dev/compare/d6bf0d1e7dac4f4820e5c16ca14a162717b5818d..920d286d8da398797738fbfd1eaf02e1f887e306
>     [4]
>     8217340:
>     https://github.com/voitylov/jdk11u-dev/commit/01542ba865c518c2b5d827d6c0b95488129b658a
>     8247592:
>     https://github.com/voitylov/jdk11u-dev/commit/48a1e49807cc189cd23c569f4b28f20282010ffd
>     8245938:
>     https://github.com/voitylov/jdk11u-dev/commit/3e41399c3471c6664302e6487d8003ecaff5e23a
>     8252248:
>     https://github.com/voitylov/jdk11u-dev/commit/bd2a506a2f44e7e2c9a0007f256e5c2288cfbe34
>     8252250:
>     https://github.com/voitylov/jdk11u-dev/commit/41b6b490fe60c640c90d9e594557215e669955cc
>     8247589:
>     https://github.com/voitylov/jdk11u-dev/commit/b0562ab5e2aa23f27803832f3854f0538f51b891
>     8247591:
>     https://github.com/voitylov/jdk11u-dev/commit/920d286d8da398797738fbfd1eaf02e1f887e306
>
>