On 7/27/2016 11:31 AM, Christoph Lameter wrote:
Ok here is a possible patch that explicitly checks for housekeeping cpus:
Subject: clocksource: Do not schedule watchdog on isolated or NOHZ cpus
watchdog checks can only run on housekeeping capable cpus. Otherwise
we will be generating noise that we would like to avoid on the isolated
processors.
Signed-off-by: Christoph Lameter <[email protected]>
Index: linux/kernel/time/clocksource.c
===================================================================
--- linux.orig/kernel/time/clocksource.c 2016-07-27 08:41:17.109862517
-0500
+++ linux/kernel/time/clocksource.c 2016-07-27 10:28:31.172447732 -0500
@@ -269,9 +269,12 @@ static void clocksource_watchdog(unsigne
* Cycle through CPUs to check if the CPUs stay synchronized
* to each other.
*/
- next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
- if (next_cpu >= nr_cpu_ids)
- next_cpu = cpumask_first(cpu_online_mask);
+ do {
+ next_cpu = cpumask_next(raw_smp_processor_id(),
cpu_online_mask);
+ if (next_cpu >= nr_cpu_ids)
+ next_cpu = cpumask_first(cpu_online_mask);
+ } while (!is_housekeeping_cpu(next_cpu));
+
watchdog_timer.expires += WATCHDOG_INTERVAL;
add_timer_on(&watchdog_timer, next_cpu);
out:
How about using cpumask_next_and(raw_smp_processor_id(), cpu_online_mask,
housekeeping_cpumask()), likewise cpumask_first_and()? Does that work?
Note that you should also cpumask_first_and() in clocksource_start_watchdog(),
just to be complete.
Hopefully the init code runs after tick_init(). It seems like that's probably
true.
--
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com
