linux-kernel - [PATCH] sched/fair: Invoke cpufreq hooks for CONFIG

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Date:	Fri, 06 May 2016 14:58:43 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Steve Muckle <steve.muckle@...aro.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: [PATCH] sched/fair: Invoke cpufreq hooks for CONFIG_SMP unset

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Commit 34e2c555f3e1 (cpufreq: Add mechanism for registering utilization
update callbacks) overlooked the fact that update_load_avg(), where
CFS invokes cpufreq utilization update hooks, becomes an empty stub for
CONFIG_SMP unset.  In consequence, if CONFIG_SMP is not set, cpufreq
governors are never invoked from CFS and they do not have a chance to
evaluate CPU performace levels and update them often enough.  Needless
to say, things don't work as expected then.

Fix the problem by making the !CONFIG_SMP stub of update_load_avg()
invoke cpufreq update hooks too.

Fixes: 34e2c555f3e1 (cpufreq: Add mechanism for registering utilization update callbacks)
Reported-by: Steve Muckle <steve.muckle@...aro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---

This needs to go into v4.6.

---
 kernel/sched/fair.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

Index: linux-pm/kernel/sched/fair.c
===================================================================
--- linux-pm.orig/kernel/sched/fair.c
+++ linux-pm/kernel/sched/fair.c
@@ -3030,7 +3030,14 @@ static int idle_balance(struct rq *this_

 #else /* CONFIG_SMP */

-static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
+static inline void update_load_avg(struct sched_entity *se, int not_used)
+{
+	struct cfs_rq *cfs_rq = cfs_rq_of(se);
+	struct rq *rq = rq_of(cfs_rq);
+
+	cpufreq_trigger_update(rq_clock(rq));
+}
+
 static inline void
 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
 static inline void