[PATCH 4.14 133/159] powerpc/watchdog: Do not trigger SMP crash from touch_nmi_watchdog

Greg Kroah-Hartman
2017-12-22T09:21:24Z

From: Nicholas Piggin <npiggin@gmail.com>

[ Upstream commit 80e4d70b06863e0104e5a0dc78aa3710297fbd4b ]

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.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/powerpc/kernel/watchdog.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -276,9 +276,12 @@ 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);