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[193.116.203.247]) by smtp.gmail.com with ESMTPSA id m12-20020a170902f64c00b0016bf9437766sm5346915plg.261.2022.07.11.18.42.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 Jul 2022 18:42:57 -0700 (PDT) Date: Tue, 12 Jul 2022 11:42:52 +1000 From: Nicholas Piggin Subject: Re: [PATCH v3 3/4] powerpc/watchdog: introduce a NMI watchdog's factor To: benh@kernel.crashing.org, haren@linux.vnet.ibm.com, Laurent Dufour , linux@roeck-us.net, mpe@ellerman.id.au, nathanl@linux.ibm.com, paulus@samba.org, wim@linux-watchdog.org Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-watchdog@vger.kernel.org References: <20220627135347.32624-1-ldufour@linux.ibm.com> <20220627135347.32624-4-ldufour@linux.ibm.com> In-Reply-To: <20220627135347.32624-4-ldufour@linux.ibm.com> MIME-Version: 1.0 Message-Id: <1657589870.vvurapsif3.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Excerpts from Laurent Dufour's message of June 27, 2022 11:53 pm: > Introduce a factor which would apply to the NMI watchdog timeout. >=20 > 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. >=20 > 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?=20 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 >=20 > Signed-off-by: Laurent Dufour > --- > arch/powerpc/include/asm/nmi.h | 2 ++ > arch/powerpc/kernel/watchdog.c | 21 ++++++++++++++++++++- > 2 files changed, 22 insertions(+), 1 deletion(-) >=20 > diff --git a/arch/powerpc/include/asm/nmi.h b/arch/powerpc/include/asm/nm= i.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 > =20 > #ifdef CONFIG_NMI_IPI > diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdo= g.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; > =20 > +#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) > =20 > static void watchdog_calc_timeouts(void) > { > - wd_panic_timeout_tb =3D watchdog_thresh * ppc_tb_freq; > + u64 threshold =3D watchdog_thresh; > + > +#ifdef CONFIG_PPC_PSERIES > + threshold +=3D (READ_ONCE(wd_factor) * threshold) / 100; > +#endif > + > + wd_panic_timeout_tb =3D threshold * ppc_tb_freq; > =20 > /* Have the SMP detector trigger a bit later */ > wd_smp_panic_timeout_tb =3D 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 > --=20 > 2.36.1 >=20 >=20