[aarch64-port-dev ] Tracking aarch64 downstream backports

[Aleksey Shipilev]

Hi,

We have the backports monitor [1] that tracks the status for the patches across the repositories.
For example, for AArch64-specific problems it currently prints this:

> JDK-8219698: aarch64: SIGILL triggered when specifying unsupported hardware features
> 
>   Original Bug:
>       URL: https://bugs.openjdk.java.net/browse/JDK-8219698
>       Reporter: Felix Yang
>       Assignee: Felix Yang
>       Priority: P4
>       Components: hotspot/runtime
> 
>   Original Fix:
>         13: JDK-8219698, http://hg.openjdk.java.net/jdk/jdk/rev/72ce7dd54939, 57 day(s) ago
> 
>   Backports and Forwardports:
>         12: 12.0.2, JDK-8220537, http://hg.openjdk.java.net/jdk-updates/jdk12u/rev/bc3f5be06d88, 44 day(s) ago
>         11: 11.0.4, JDK-8220535, http://hg.openjdk.java.net/jdk-updates/jdk11u-dev/rev/e0d47c058971, 44 day(s) ago
>          8: MISSING
>          7: Not affected

Notice "8: MISSING" -- it says that while the issue has the "Affected Versions: 8", and there is no
corresponding backport in 8u. Which stands to reason, as aarch64-port is not in mainline 8u.

We have the same issue with Shenandoah 8u and 11u development forests: Shenandoah is not in mainline
there. So, we got ourselves a workaround: the backport monitor parses the Mercurial repositories,
and looks for the matching bug ID lines, if the issue has the "Affected Versions" either
"8-shenandoah" or "11-shenandoah", like this:

> JDK-8220712: [TESTBUG] gc/shenandoah/compiler/TestMaybeNullUnsafeAccess should run with Shenandoah enabled
> 
>   Original Bug:
>       URL: https://bugs.openjdk.java.net/browse/JDK-8220712
>       Reporter: Aleksey Shipilev
>       Assignee: Aleksey Shipilev
>       Priority: P4
>       Components: hotspot/gc
> 
>   Original Fix:
>         13: JDK-8220712, http://hg.openjdk.java.net/jdk/jdk/rev/6f14d52d5e10, 41 day(s) ago
> 
>   Backports and Forwardports:
>         12: 12.0.2, JDK-8221572, http://hg.openjdk.java.net/jdk-updates/jdk12u/rev/8e7e0aa6882b, 29 day(s) ago
>         11: Not affected
>          8: Not affected
>          7: Not affected
> 
>   Shenandoah Backports:
>         11: shenandoah-jdk-11.0.3+6, https://hg.openjdk.java.net/shenandoah/jdk11//rev/5cf51abddfbe
>          8: MISSING

Notice the "Shenandoah Backports" section.

We can do the same for AArch64-port. To do this, we need Project Lead to ask ops@ for a special
version tag (e.g. "8-aarch64" or something) in JIRA, and then we put this new version tag instead of
plain "8" on issues that affect only the downstream aarch64-8u code. (Then I'll do some adjustments
to backport monitor to handle that new thing).

-- 
Thanks,
-Aleksey

[1] https://builds.shipilev.net/backports-monitor/label-actionable-redhat-openjdk.txt