Re: [PATCH v2 2/6] watchdog/hardlockup: Make the config checks more straightforward

Doug Anderson
2023-06-16T16:48:16Z

Hi,

On Fri, Jun 16, 2023 at 8:07 AM Petr Mladek <pmladek@suse.com> wrote:
>
> There are four possible variants of hardlockup detectors:
>
> + buddy: available when SMP is set.
>
> + perf: available when HAVE_HARDLOCKUP_DETECTOR_PERF is set.
>
> + arch-specific: available when HAVE_HARDLOCKUP_DETECTOR_ARCH is set.
>
> + sparc64 special variant: available when HAVE_NMI_WATCHDOG is set
> and HAVE_HARDLOCKUP_DETECTOR_ARCH is not set.
>
> The check for the sparc64 variant is more complicated because
> HAVE_NMI_WATCHDOG is used to #ifdef code used by both arch-specific
> and sparc64 specific variant. Therefore it is automatically
> selected with HAVE_HARDLOCKUP_DETECTOR_ARCH.
>
> This complexity is partly hidden in HAVE_HARDLOCKUP_DETECTOR_NON_ARCH.
> It reduces the size of some checks but it makes them harder to follow.
>
> Finally, the other temporary variable HARDLOCKUP_DETECTOR_NON_ARCH
> is used to re-compute HARDLOCKUP_DETECTOR_PERF/BUDDY when the global
> HARDLOCKUP_DETECTOR switch is enabled/disabled.
>
> Make the logic more straightforward by the following changes:
>
> + Better explain the role of HAVE_HARDLOCKUP_DETECTOR_ARCH and
> HAVE_NMI_WATCHDOG in comments.
>
> + Add HAVE_HARDLOCKUP_DETECTOR_BUDDY so that there is separate
> HAVE_* for all four hardlockup detector variants.
>
> Use it in the other conditions instead of SMP. It makes it
> clear that it is about the buddy detector.
>
> + Open code HAVE_HARDLOCKUP_DETECTOR_NON_ARCH in HARDLOCKUP_DETECTOR
> and HARDLOCKUP_DETECTOR_PREFER_BUDDY. It helps to understand
> the conditions between the four hardlockup detector variants.
>
> + Define the exact conditions when HARDLOCKUP_DETECTOR_PERF/BUDDY
> can be enabled. It explains the dependency on the other
> hardlockup detector variants.
>
> Also it allows to remove HARDLOCKUP_DETECTOR_NON_ARCH by using "imply".
> It triggers re-evaluating HARDLOCKUP_DETECTOR_PERF/BUDDY when
> the global HARDLOCKUP_DETECTOR switch is changed.
>
> + Add dependency on HARDLOCKUP_DETECTOR so that the affected variables
> disappear when the hardlockup detectors are disabled.
>
> Another nice side effect is that HARDLOCKUP_DETECTOR_PREFER_BUDDY
> value is not preserved when the global switch is disabled.
> The user has to make the decision again when it gets re-enabled.
>
> Signed-off-by: Petr Mladek <pmladek@suse.com>
> ---
> arch/Kconfig | 23 +++++++++++++-----
> lib/Kconfig.debug | 62 +++++++++++++++++++++++++++--------------------
> 2 files changed, 53 insertions(+), 32 deletions(-)

While I'd still paint the bikeshed a different color and organize the
dependencies a little differently, as discussed in your v1 post, this
is still OK w/ me.

Reviewed-by: Douglas Anderson <dianders@chromium.org>