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From: Dmitry Vyukov <dvyukov@google.com>
Date: Tue, 9 Apr 2024 13:45:24 +0200
Message-ID: <CACT4Y+ZOn3n+NL=JH-=yNWOv8RWOg_idGqQz10fD-F-FW27M+g@mail.gmail.com>
Subject: Re: [PATCH] selftests/timers/posix_timers: reimplement check_timer_distribution()
To: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, John Stultz <jstultz@google.com>, 
	Marco Elver <elver@google.com>, Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>, 
	"Eric W. Biederman" <ebiederm@xmission.com>, linux-kernel@vger.kernel.org, 
	linux-kselftest@vger.kernel.org, kasan-dev@googlegroups.com, 
	Edward Liaw <edliaw@google.com>, Carlos Llamas <cmllamas@google.com>, 
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Content-Type: text/plain; charset="UTF-8"

On Tue, 9 Apr 2024 at 13:12, Oleg Nesterov <oleg@redhat.com> wrote:
>
> On 04/09, Thomas Gleixner wrote:
> >
> > The discussion started about running new tests on older kernels. As this
> > is a feature and not a bug fix that obviously fails on older kernels.
>
> OK, I see... please see below.
>
> > So something like the uncompiled below should work.
>
> Hmm... this patch doesn't apply to Linus's tree...
>
> It seems that this is because in your tree check_timer_distribution() does
>
>         if (timer_delete(id)) {
>                 ksft_perror("Can't delete timer");
>                 return 0;
>         }
>
> while in Linus's tree it returns -1 if timer_delete() fails. Nevermind.
>
> Thomas, I am almost shy to continue this discussion and waste your time ;)
> But ...
>
> > +static bool check_kernel_version(unsigned int min_major, unsigned int min_minor)
> > +{
> > +     unsigned int major, minor;
> > +     struct utsname info;
> > +
> > +     uname(&info);
> > +     if (sscanf(info.release, "%u.%u.", &major, &minor) != 2)
> > +             ksft_exit_fail();
> > +     return major > min_major || (major == min_major && minor >= min_minor);
> > +}
>
> this looks useful regardless. Perhaps it should be moved into
> tools/testing/selftests/kselftest.h as ksft_ck_kernel_version() ?
>
> > +static int check_timer_distribution(void)
> > +{
> > +     const char *errmsg;
> > +
> > +     if (!check_kernel_version(6, 3)) {
> > +             ksft_test_result_skip("check signal distribution (old kernel)\n");
> >               return 0;
>
> ...
>
> > +     ksft_test_result(!ctd_failed, "check signal distribution\n");
>
> Perhaps
>
>         if (!ctd_failed)
>                 ksft_test_result_pass("check signal distribution\n");
>         else if (check_kernel_version(6, 3))
>                 ksft_test_result_fail("check signal distribution\n");
>         else
>                 ksft_test_result_skip("check signal distribution (old kernel)\n");
>
> makes more sense?

This looks even better!

> This way it can be used on the older kernels with bcb7ee79029d backported.
>
> Oleg.
>