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powerpc/watchdog: Moderate touch_nmi_watchdog overhead

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Some code can go into a tight loop calling touch_nmi_watchdog (e.g.,
stop_machine CPU hotplug code). This can cause contention on watchdog
locks particularly if all CPUs with watchdog enabled are spinning in
the loops.

Avoid this storm of activity by running the watchdog timer callback
from this path if we have exceeded the timer period since it was last
run.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin 2017-08-09 22:41:23 +10:00 committed by Michael Ellerman
parent d8e2a40535
commit 26c5c6e129
1 changed files with 3 additions and 1 deletions
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4
arch/powerpc/kernel/watchdog.c
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@ -263,9 +263,11 @@ static void wd_timer_fn(unsigned long data)
void arch_touch_nmi_watchdog(void)
{
unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000;
int cpu = smp_processor_id();
watchdog_timer_interrupt(cpu);
if (get_tb() - per_cpu(wd_timer_tb, cpu) >= ticks)
watchdog_timer_interrupt(cpu);
}
EXPORT_SYMBOL(arch_touch_nmi_watchdog);