linux-kernel - [PATCH v14 11/14] clocksource: Do not schedule watchdog on isolated or NOHZ cpus

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Message-Id: <1470774596-17341-12-git-send-email-cmetcalf@mellanox.com>
Date:	Tue,  9 Aug 2016 16:29:53 -0400
From:	Chris Metcalf <cmetcalf@...lanox.com>
To:	Gilad Ben Yossef <giladb@...lanox.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Andy Lutomirski <luto@...capital.net>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Cc:	Chris Metcalf <cmetcalf@...lanox.com>
Subject: [PATCH v14 11/14] clocksource: Do not schedule watchdog on isolated or NOHZ cpus

From: Christoph Lameter <cl@...ux.com>

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 <cl@...ux.com>
Signed-off-by: Chris Metcalf <cmetcalf@...lanox.com>
  [line-wrapped and added equivalent fix in clocksource_start_watchdog()]
---
 kernel/time/clocksource.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 6a5a310a1a53..b9c79c96d069 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -269,9 +269,12 @@ static void clocksource_watchdog(unsigned long data)
 	 * Cycle through CPUs to check if the CPUs stay synchronized
 	 * to each other.
 	 */
-	next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
+	next_cpu = cpumask_next_and(raw_smp_processor_id(), cpu_online_mask,
+				    housekeeping_cpumask());
 	if (next_cpu >= nr_cpu_ids)
-		next_cpu = cpumask_first(cpu_online_mask);
+		next_cpu = cpumask_first_and(cpu_online_mask,
+					     housekeeping_cpumask());
+
 	watchdog_timer.expires += WATCHDOG_INTERVAL;
 	add_timer_on(&watchdog_timer, next_cpu);
 out:
@@ -285,7 +288,8 @@ static inline void clocksource_start_watchdog(void)
 	init_timer(&watchdog_timer);
 	watchdog_timer.function = clocksource_watchdog;
 	watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
-	add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
+	add_timer_on(&watchdog_timer,
+		     cpumask_first_and(cpu_online_mask, housekeeping_cpumask()));
 	watchdog_running = 1;
 }
 
-- 
2.7.2