NACK: [SRU][L, K, J, F][M, U][PATCH v2 0/1] UBUNTU: [Packaging] Expose base (parent) abinum for derivatives

Tue Jun 6 10:43:42 UTC 2023

On Tue, Jun 06, 2023 at 11:47:08AM +0200, Roxana Nicolescu wrote:
> BugLink: https://bugs.launchpad.net/bugs/2017006
> 
> SRU Justification
> 

See NACK for v1.

> [ Impact ]
> 
> Upstream stable added a change in the format of jbd2 in 5.15.87 that
> was cherry-picked to kinetic:linux.
> This is incompatible with the current changes in the lttng-module
> kinetic.
> 
> We previously encountered this issue for focal #lp2004644
> and we proactively released a new version for kinetic, but the fix did
> not work as expected.
> 
> As shown in the buglink, the build error is triggered because some
> function declaration does not match the kernel's.
> In `include/instrumentation/events/jbd2.h` in lttng-modules, there is
> a conditional declaration based on the kernel version.
> But for 5.19 kernels, the upstream kernel version has remained the
> same.
> 
> [ Fix ]
> Versioning based on linux upstream version does not work in this case.
> We expose the abi version of the kernel, but it alone will not solve
> this issue because we deliver many derivatives, each with its own
> version. Hence a base main abi version needs to be exposed in the
> headers.
> 
> The actual fix for lttng-modules requires 2 steps:
> 1. Expose UTS_UBUNTU_BASE_RELEASE_ABI variable equal with the parent
> abi in <generated/utsrelease.h>. For backports with multiple
> inheritance (like jammy:linux-aws-5.19) the version from debian.master
> (kinetic:linux) will be used. In case there is no inheritance, the
> actual kernel abi will be used. This is needed for jammy, kinetic and
> lunar but it may be needed in the future for similar use cases,
> so it makes sense to push this to all releases.
> This patch will cover the first part.
> 2. Use this variable in the lttng-module to construct
> LTTNG_UBUNTU_BASE_VERSION_CODE and then use it for versioning:
> LTTNG_UBUNTU_BASE_VERSION_CODE >= LTTNG_UBUNTU_KERNEL_VERSION(5,19,0,42)
> The lttng-module fix will be done only for lunar, kinetic, and jammy.
> 
> [ Where problems would occur ]
> This patch alone should not have a big impact on our kernels.
> It will only expose a variable in the headers.
> In terms of the lttng-modules solution:
> We may notice new failures in ubuntu_lttng_smoke_test once this
> compiles and run. But it was tested locally and the results were good,
> so the probability is very very low.
> 
> [ Test Plan ]
> Since we hit backward issues in the past, multiple kernel versions
> were tested out to make sure this is the proper fix.
> General test instructions:
> 1. Install kinetic (desired version)
> 2. sudo apt install lttng-modules-dkms(or dpkg -i)
> 3. Depending on the version it may work or not
> 4. Additionally lttng-modules regression test should be triggered to
> confirm everything works fine.
> 
> My testing:
> I build fixed lttng-modules with the fixes described in launchpad.
> A. Kinetic kernel where I expose UTS_UBUNTU_BASE_RELEASE_ABI.
> The module built and rts passed:
> 09:32:05 INFO | PASSED (simple system call tracing with babeltrace)
> 09:32:05 INFO | Summary: 7 passed, 0 failed
> B. The break commit was introduced in 5.19.0.42. Versions between 42
> and 44 (depending on where this fix will land) will break.
> C. Tested with a kernel version that does not have the break commit:
> 5.19.0-41 to see if it's backwards compatible. Results were good.
> D. Tested with jammy-aws-5.19 that has this patch. It works fine.
> E. Tested with jammy-aws-5.19.0-1024 that does not have the break
> commit to see backwards compatibility. It succeeded.
> 
> Changes since v1:
> - used a cleaner version of parsing the abinum from
>   debian.master/changelog that lead to removing the useless variables
>   created in v1
> - added abinum in the title
> 
> Roxana Nicolescu (1):
>   UBUNTU: [Packaging] Expose base (parent) abinum for derivatives
> 
>  debian/rules.d/0-common-vars.mk | 6 ++++++
>  debian/rules.d/2-binary-arch.mk | 4 ++++
>  2 files changed, 10 insertions(+)
> 
> -- 
> 2.34.1
> 
> 
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