[PATCH v5 3/4] powerpc/watchdog: introduce a NMI watchdog's factor

From: Laurent Dufour <ldufour@linux.ibm.com>
To: mpe@ellerman.id.au, npiggin@gmail.com,
	christophe.leroy@csgroup.eu, wim@linux-watchdog.org,
	linux@roeck-us.net, nathanl@linux.ibm.com, rdunlap@infradead.org
Cc: haren@linux.vnet.ibm.com, hch@infradead.org,
	linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-watchdog@vger.kernel.org
Subject: [PATCH v5 3/4] powerpc/watchdog: introduce a NMI watchdog's factor
Date: Wed, 13 Jul 2022 17:47:28 +0200	[thread overview]
Message-ID: <20220713154729.80789-4-ldufour@linux.ibm.com> (raw)
In-Reply-To: <20220713154729.80789-1-ldufour@linux.ibm.com>

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.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
---
 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..c3c7adef74de 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_timeout_pct(u64 pct);
 #else
 static inline void arch_touch_nmi_watchdog(void) {}
+static inline void watchdog_nmi_set_timeout_pct(u64 pct) {}
 #endif
 
 #ifdef CONFIG_NMI_IPI
diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index 7d28b9553654..5d903e63f932 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_timeout_pct;
+#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_timeout_pct) * 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_timeout_pct(u64 pct)
+{
+	pr_info("Set the NMI watchdog timeout factor to %llu%%\n", pct);
+	WRITE_ONCE(wd_timeout_pct, pct);
+	lockup_detector_reconfigure();
+}
+#endif
-- 
2.37.0

