Excerpts from Laurent Dufour's message of June 27, 2022 11:53 pm:
> Introduce a factor which would apply to the NMI watchdog timeout.
>
> This factor is a percentage added to the watchdog_tresh value. The value is
> set under the watchdog_mutex protection and lockup_detector_reconfigure()
> is called to recompute wd_panic_timeout_tb.
>
> Once the factor is set, it remains until it is set back to 0, which means
> no impact.
Looks okay. We could worry about making it more generic or nicer if
another user came along.
Could you make the naming a bit more self documenting?
watchdog_nmi_set_timeout_pct(), maybe? Does the wd really care
that it is for LPM in particular?
Variables and parameters could have a _pct suffix too.
Otherwise
Reviewed-by: Nicholas Piggin <npiggin@xxxxxxxxx>
>
> Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxx>
> ---
> arch/powerpc/include/asm/nmi.h | 2 ++
> arch/powerpc/kernel/watchdog.c | 21 ++++++++++++++++++++-
> 2 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/include/asm/nmi.h b/arch/powerpc/include/asm/nmi.h
> index ea0e487f87b1..7d6a8d9b0543 100644
> --- a/arch/powerpc/include/asm/nmi.h
> +++ b/arch/powerpc/include/asm/nmi.h
> @@ -5,8 +5,10 @@
> #ifdef CONFIG_PPC_WATCHDOG
> extern void arch_touch_nmi_watchdog(void);
> long soft_nmi_interrupt(struct pt_regs *regs);
> +void watchdog_nmi_set_lpm_factor(u64 factor);
> #else
> static inline void arch_touch_nmi_watchdog(void) {}
> +static inline void watchdog_nmi_set_lpm_factor(u64 factor) {}
> #endif
>
> #ifdef CONFIG_NMI_IPI
> diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
> index 7d28b9553654..80851b228f71 100644
> --- a/arch/powerpc/kernel/watchdog.c
> +++ b/arch/powerpc/kernel/watchdog.c
> @@ -91,6 +91,10 @@ static cpumask_t wd_smp_cpus_pending;
> static cpumask_t wd_smp_cpus_stuck;
> static u64 wd_smp_last_reset_tb;
>
> +#ifdef CONFIG_PPC_PSERIES
> +static u64 wd_factor;
> +#endif
> +
> /*
> * Try to take the exclusive watchdog action / NMI IPI / printing lock.
> * wd_smp_lock must be held. If this fails, we should return and wait
> @@ -527,7 +531,13 @@ static int stop_watchdog_on_cpu(unsigned int cpu)
>
> static void watchdog_calc_timeouts(void)
> {
> - wd_panic_timeout_tb = watchdog_thresh * ppc_tb_freq;
> + u64 threshold = watchdog_thresh;
> +
> +#ifdef CONFIG_PPC_PSERIES
> + threshold += (READ_ONCE(wd_factor) * threshold) / 100;
> +#endif
> +
> + wd_panic_timeout_tb = threshold * ppc_tb_freq;
>
> /* Have the SMP detector trigger a bit later */
> wd_smp_panic_timeout_tb = wd_panic_timeout_tb * 3 / 2;
> @@ -570,3 +580,12 @@ int __init watchdog_nmi_probe(void)
> }
> return 0;
> }
> +
> +#ifdef CONFIG_PPC_PSERIES
> +void watchdog_nmi_set_lpm_factor(u64 factor)
> +{
> + pr_info("Set the NMI watchdog factor to %llu%%\n", factor);
> + WRITE_ONCE(wd_factor, factor);
> + lockup_detector_reconfigure();
> +}
> +#endif
> --
> 2.36.1
>
>
