sched/fair: Fix !CONFIG_SMP kernel cpufreq governor breakage

rafaeljw · Ingo Molnar · commit 536bd00cdbb7 · 2016-05-07T07:45:34.000+02:00
The following commit: 34e2c55 ("cpufreq: Add mechanism for registering utilization update callbacks") overlooked the fact that update_load_avg(), where CFS invokes cpufreq utilization update callbacks, becomes an empty stub on UP kernels. In consequence, if !CONFIG_SMP, 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 callbacks too. Reported-by: Steve Muckle <steve.muckle@linaro.org> Tested-by: Steve Muckle <steve.muckle@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Steve Muckle <steve.muckle@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Linux PM list <linux-pm@vger.kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Viresh Kumar <viresh.kumar@linaro.org> Fixes: 34e2c55 (cpufreq: Add mechanism for registering utilization update callbacks) Link: http://lkml.kernel.org/r/6282396.VVEdgVYxO3@vostro.rjw.lan Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
@@ -3030,7 +3030,14 @@ static int idle_balance(struct rq *this_rq);
 
 #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
