Re: [PATCH] selftests: remove obsolete kconfig fragment for cpu-hotplug

[lyang0]

On 2017å11æ03æ 11:55, Sumit Semwal wrote:
> Hello Lei,
>
> On 2 November 2017 at 07:43, lyang0 <lei.yang@xxxxxxxxxxxxx> wrote:
> > On 2017å11æ02æ 06:59, Shuah Khan wrote:
> > > On 11/01/2017 04:52 PM, Thomas Gleixner wrote:
> > > > On Wed, 1 Nov 2017, Shuah Khan wrote:
> > > > > On 10/17/2017 08:10 PM, lei.yang@xxxxxxxxxxxxx wrote:
> > > > > > From: Lei Yang <Lei.Yang@xxxxxxxxxxxxx>
> > > > > >
> > > > > > Kconfig CONFIG_CPU_NOTIFIER_ERROR_INJECT has been removed since kernel
> > > > > > 4.10
> > > > > > check commit:
> > > > > >       commit 530e9b76ae8f863dfdef4a6ad0b38613d32e8c3f
> > > > > >       Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > > > > >       Date:   Wed Dec 21 20:19:53 2016 +0100
> > > > > >
> > > > > >           cpu/hotplug: Remove obsolete cpu hotplug register/unregister
> > > > > > functions
> > > > > >
> > > > > >           hotcpu_notifier(), cpu_notifier(), __hotcpu_notifier(),
> > > > > > __cpu_notifier(),
> > > > > >           register_hotcpu_notifier(), register_cpu_notifier(),
> > > > > >           __register_hotcpu_notifier(), __register_cpu_notifier(),
> > > > > >           unregister_hotcpu_notifier(), unregister_cpu_notifier(),
> > > > > >           __unregister_hotcpu_notifier(), __unregister_cpu_notifier()
> > > > > >        <snip>
> > > > > >
> > > > > > Signed-off-by: Lei Yang <Lei.Yang@xxxxxxxxxxxxx>
> > > > > > ---
> > > > > >    tools/testing/selftests/cpu-hotplug/config | 1 -
> > > > > >    1 file changed, 1 deletion(-)
> > > > > >
> > > > > > diff --git a/tools/testing/selftests/cpu-hotplug/config
> > > > > > b/tools/testing/selftests/cpu-hotplug/config
> > > > > > index e6ab090..d4aca2a 100644
> > > > > > --- a/tools/testing/selftests/cpu-hotplug/config
> > > > > > +++ b/tools/testing/selftests/cpu-hotplug/config
> > > > > > @@ -1,2 +1 @@
> > > > > >    CONFIG_NOTIFIER_ERROR_INJECTION=y
> > > > > > -CONFIG_CPU_NOTIFIER_ERROR_INJECT=m
> > > > > Yes. It is removed from the kernel. However, selftests from the latest
> > > > > release do get run routinely on older stable releases. Dropping the
> > > > > config will impact coverage on older releases.
> > > > >
> > > > > Thomas/Greg,
> > > > >
> > > > > Any ideas on what we should do about this. On one hand it is a good idea
> > > > > to remove it, however my concern is coverage on older releases.
> > > > Can you check the kernel version on which you are running and do it
> > > > runtime
> > > > conditionally?
> > > I have been avoiding adding kernel version checks to tests. Maybe this is
> > > one exception since the functionality is obsoleted.
> >
> >
> > I think the baseline is that we only assure kselftest  works on the release
> > it belongs to, for example, removing this config for the
> > version above 4.10, keep it in old release.  but looks it doesn't work like
> > this way.
> >
> > I think We can't  assure latest kselftest works still well on a very older
> > releases
> > yes, for some features it's common for each release. but we have some
> > features that are only available in newer
> > release.   even for the common features, it's difficult to make sure it
> > still works well for each
> > release. maintenance is a big effort if we use something like version check.
> > you never know what changes will make
> > for general feature in the future release although it's common right now.
> As Greg and several others have reiterated - the tests should be able
> to check for presence of a feature, run it if it's applicable, and
> skip if it's not. It really isn't about kernel version check, but
> writing code and test in such a way that tests can 'degrade
> gracefully', rather than fail. There are several good examples for the
> same.
>
> The idea of running newer tests is to gain coverage on older kernels
> for features still present in them, but tests weren't available at the
> time of the kernel tagging.

so we actually don't have version control for kselftest?  anytime, we 
use the latest one

I thought  we recommended use the one in 4.12 if we want to test 4.12 
kernel, not to use the one in newer version



> Hope this helps clear the doubt?

I'm wondering how do you determine this patch apply to which release.

I don't understand "Dropping the config will impact coverage on older 
releases" , we can just don't apply it to
the release older than 4.10.  then the coverage doesn't drop.

Lei



> > Lei
> >
> >
> > > In any case, just removing the config isn't the complete solution. I will
> > > have to think about this some.
> > >
> > > thanks,
> > > -- Shuah
> > >
> > > --
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> Best,
> Sumit.
> --
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