Subject: Re: [RFC PATCH v2 09/14] watchdog/hardlockup: Make arch_touch_nmi_watchdog() to hpet-based implementation

From: "Paul E. McKenney" <[email-masked]>
Date: Wed, 27 Feb 2019 08:17:58 -0800

On Wed, Feb 27, 2019 at 08:05:13AM -0800, Ricardo Neri wrote:
> CPU architectures that have an NMI watchdog use arch_touch_nmi_watchdog()
> to briefly ignore the hardlockup detector. If the architecture does not
> have an NMI watchdog, one can be constructed using a source of non-
> maskable interrupts. In this case, arch_touch_nmi_watchdog() is common
> to any underlying hardware resource used to drive the detector and needs
> to be available to other kernel subsystems if hardware different from perf
> drives the detector.
> 
> There exists perf-based and HPET-based implementations. Make it available
> to the latter.
> 
> For clarity, wrap this function in a separate preprocessor conditional
> from functions which are truly specific to the perf-based implementation.
> 
> Cc: "H. Peter Anvin" <[email-masked]>
> Cc: Ashok Raj <[email-masked]>
> Cc: Andi Kleen <[email-masked]>
> Cc: Tony Luck <[email-masked]>
> Cc: "Rafael J. Wysocki" <[email-masked]>
> Cc: Don Zickus <[email-masked]>
> Cc: Nicholas Piggin <[email-masked]>
> Cc: Michael Ellerman <[email-masked]>
> Cc: Frederic Weisbecker <[email-masked]>
> Cc: Alexei Starovoitov <[email-masked]>
> Cc: Babu Moger <[email-masked]>
> Cc: "David S. Miller" <[email-masked]>
> Cc: Benjamin Herrenschmidt <[email-masked]>
> Cc: Paul Mackerras <[email-masked]>
> Cc: Mathieu Desnoyers <[email-masked]>
> Cc: Masami Hiramatsu <[email-masked]>
> Cc: Peter Zijlstra <[email-masked]>
> Cc: Andrew Morton <[email-masked]>
> Cc: Philippe Ombredanne <[email-masked]>
> Cc: Colin Ian King <[email-masked]>
> Cc: Byungchul Park <[email-masked]>
> Cc: "Paul E. McKenney" <[email-masked]>
> Cc: "Luis R. Rodriguez" <[email-masked]>
> Cc: Waiman Long <[email-masked]>
> Cc: Josh Poimboeuf <[email-masked]>
> Cc: Randy Dunlap <[email-masked]>
> Cc: Davidlohr Bueso <[email-masked]>
> Cc: Christoffer Dall <[email-masked]>
> Cc: Marc Zyngier <[email-masked]>
> Cc: Kai-Heng Feng <[email-masked]>
> Cc: Konrad Rzeszutek Wilk <[email-masked]>
> Cc: David Rientjes <[email-masked]>
> Cc: "Ravi V. Shankar" <[email-masked]>
> Cc: [email-masked]
> Cc: [email-masked]
> Cc: [email-masked]
> Signed-off-by: Ricardo Neri <[email-masked]>
> ---
>  include/linux/nmi.h | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/nmi.h b/include/linux/nmi.h
> index 5a8b19749769..bf5ebcfdd590 100644
> --- a/include/linux/nmi.h
> +++ b/include/linux/nmi.h
> @@ -94,8 +94,16 @@ static inline void hardlockup_detector_disable(void) {}
>  # define NMI_WATCHDOG_SYSCTL_PERM	0444
>  #endif
> 
> -#if defined(CONFIG_HARDLOCKUP_DETECTOR_PERF)
> +#if defined(CONFIG_HARDLOCKUP_DETECTOR_PERF) || \
> +    defined(CONFIG_X86_HARDLOCKUP_DETECTOR_HPET)

Why not instead make CONFIG_X86_HARDLOCKUP_DETECTOR_HPET select
CONFIG_HARDLOCKUP_DETECTOR_PERF?  Keep the arch-specific details
in the arch-specific files and all that.

							Thanx, Paul

>  extern void arch_touch_nmi_watchdog(void);
> +#else
> +# if !defined(CONFIG_HAVE_NMI_WATCHDOG)
> +static inline void arch_touch_nmi_watchdog(void) {}
> +# endif
> +#endif
> +
> +#if defined(CONFIG_HARDLOCKUP_DETECTOR_PERF)
>  extern void hardlockup_detector_perf_stop(void);
>  extern void hardlockup_detector_perf_restart(void);
>  extern void hardlockup_detector_perf_disable(void);
> -- 
> 2.17.1
>