[PATCH 0/1][bionic:linux-raspi2] CONFIG_LATENCYTOP=n

[Tim Gardner]

BugLink: https://bugs.launchpad.net/bugs/1928394

[Impact]

There were some recent changes on the main kernels to fix some syntax issues with the annotations files (Propagate "Update annotations and fix errors" to all derivatives), after I replicated the changes from bionic/linux to bionic/linux-raspi2 I started getting this enforcement error:

check-config: FAIL (y != n): CONFIG_LATENCYTOP policy<{'amd64-generic': 'n', 'amd64-lowlatency': 'y', 'arm64': 'n', 'armhf': 'n', 'i386': 'n', 'ppc64el': 'n', 's390x': 'n'}> mark<ENFORCED> note<https://lists.ubuntu.com/archives/kernel-team/2014-July/045006.html, LP#1655986>
It seems we were supposed to have the same enforcement as the main kernel (= n) but the raspi2 config has it actually enabled.

Looking at the url and the bug reference on the enforcement notes, it seems it doesn't make much sense to keep it enabled for non-lowlatency kernels.

@juerghaefliger confirmed we should disable this option:

Yes, it should be disabled. I did the same for hirsute earlier this year after Seth fixed the master config annotations:
~ubuntu-kernel/ubuntu/+source/linux-raspi/+git/hirsute - [no description]

If I remember correctly I made some other config changes due to Seth's
changes.

[Test Plan]

Install latencytop, try to run the tool.

[Where problems could occur]

Disabling this config removes information that userspace might depend on.