lttng-modules-dkms 2.4.1-1: lttng-modules kernel module failed to build [error: unknown field ‘map’ specified in initializer]

[Ted Gould]

Upgrading to Utopic

ProblemType: Package
DistroRelease: Ubuntu 14.10
Package: lttng-modules-dkms 2.4.1-1
ProcVersionSignature: Ubuntu 3.15.0-1.5-generic 3.15.0-rc5
Uname: Linux 3.15.0-1-generic x86_64
ApportVersion: 2.14.2-0ubuntu4
Architecture: amd64
DKMSKernelVersion: 3.15.0-1-generic
Date: Tue May 20 22:39:56 2014
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-precise-amd64-20130203-1
DuplicateSignature: dkms:lttng-modules-dkms:2.4.1-1:/var/lib/dkms/lttng-modules/2.4.1/build/lib/ringbuffer/ring_buffer_splice.c:59:2: error: unknown field ‘map’ specified in initializer
InstallationDate: Installed on 2013-12-13 (158 days ago)
InstallationMedia: Ubuntu 12.04 "Precise" - Build amd64 LIVE Binary 20130203-13:50
PackageArchitecture: all
PackageVersion: 2.4.1-1
SourcePackage: lttng-modules
SystemImageInfo: Error: [Errno 2] No such file or directory: 'system-image-cli'
Title: lttng-modules-dkms 2.4.1-1: lttng-modules kernel module failed to build
UpgradeStatus: Upgraded to utopic on 2013-12-21 (150 days ago)

[Alex Montplaisir (alexandre-montplaisir)]

I can reproduce the build error, it seems lttng-modules 2.4 doesn't build against kernel 3.15.

There are some commits in master to support 3.15 though, in particular:
http://git.lttng.org/?p=lttng-modules.git;a=commit;h=989f58e80ffdf6fbc3150d14977c2bff411d3b9c

I'll inquire if it's planned to backport the 3.15 support to 2.4. I guess it depends on how soon 2.5 comes out.

[Alex Montplaisir (alexandre-montplaisir)]

Due to a change in the tracepoint API between kernels 3.14 and 3.15, it's not trivial to backport the support to the 2.4 series. So 2.4 will not support kernel 3.15+.

Incidentally, LTTng 2.5 RC1 came out today. The correct solution would be to update the package to lttng-modules 2.5 then.

[Chris J Arges (arges)]

So this leaves lttng-modules in an unusable state for both Trusty (3.13) and Utopic (3.16) currently. In addition we need to consider that Trusty will be able to use newer kernels such as 3.16, and those for the V/W/X-series.

If updating to lttng-modules 2.5 is the solution; then perhaps updating the debian version to a newer version and applying for a MRE (https://wiki.ubuntu.com/StableReleaseUpdates/MicroReleaseExceptions) such that these newer releases can be pushed into the affected Ubuntu series (T and greater) makes the most sense.

In addition taking a glance at the bugs against this package the majority are DKMS compile issues; so perhaps having an MRE update would close many of those issues as well.

[Mathieu Desnoyers (mathieu-desnoyers)]

Hi,

We usually backport tracepoint instrumentation updates to support newer kernels, but as Alexandre Montplaisir pointed out, there is a significant tracepoint API change introduced in kernel 3.15 that requires the new lttng-tracepoint.c adapter, and I would consider it far-fetched to backport it as a fix. This is why we chose not to support kernels 3.15+ in lttng-modules 2.4.

Therefore, upgrading to lttng-modules 2.5 would be the appropriate solution. Please keep in mind that this is not usually required. This is a rare situation where there has been a significant module API change in the Linux kernel that required implementing a new adapter to support the new kernel.

Thanks,

Mathieu