linux-kernel - [PATCH v2 3/4] powerpc/watchdog: introduce a LPM factor

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Message-Id: <20220614135414.37746-4-ldufour@linux.ibm.com>
Date:   Tue, 14 Jun 2022 15:54:13 +0200
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
        nathanl@...ux.ibm.com, haren@...ux.vnet.ibm.com, npiggin@...il.com
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/4] powerpc/watchdog: introduce a LPM factor

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.

Signed-off-by: Laurent Dufour <ldufour@...ux.ibm.com>
---
 arch/powerpc/include/asm/nmi.h |  2 ++
 arch/powerpc/kernel/watchdog.c | 22 +++++++++++++++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/nmi.h b/arch/powerpc/include/asm/nmi.h
index ea0e487f87b1..4eb894ef12a3 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 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..faaf5ba14d69 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 += (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 +580,13 @@ int __init watchdog_nmi_probe(void)
 	}
 	return 0;
 }
+
+#ifdef CONFIG_PPC_PSERIES
+void watchdog_nmi_set_lpm_factor(u64 factor)
+{
+	mutex_lock(&watchdog_mutex);
+	wd_factor = factor;
+	lockup_detector_reconfigure();
+	mutex_unlock(&watchdog_mutex);
+}
+#endif
-- 
2.36.1