Subject: [PATCH v2 3/6] powerpc/watchdog: do not trigger SMP crash from touch_nmi_watchdog

From: Nicholas Piggin <[email-masked]>
Date: Fri, 29 Sep 2017 13:29:39 +1000

In xmon, touch_nmi_watchdog() is not expected to be checking that
other CPUs have not touched the watchdog, so the code will just
call touch_nmi_watchdog() once before re-enabling hard interrupts.

Just update our CPU's state, and ignore apparently stuck SMP threads.

Arguably touch_nmi_watchdog should check for SMP lockups, and
callers should be fixed, but that's not trivial for the input code
of xmon.
---
 arch/powerpc/kernel/watchdog.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index 920e61c79f47..1fb9379dc683 100644
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -277,9 +277,12 @@ void arch_touch_nmi_watchdog(void)
 {
 	unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000;
 	int cpu = smp_processor_id();
+	u64 tb = get_tb();
 
-	if (get_tb() - per_cpu(wd_timer_tb, cpu) >= ticks)
-		watchdog_timer_interrupt(cpu);
+	if (tb - per_cpu(wd_timer_tb, cpu) >= ticks) {
+		per_cpu(wd_timer_tb, cpu) = tb;
+		wd_smp_clear_cpu_pending(cpu, tb);
+	}
 }
 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
 
-- 
2.13.3