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Commit a2129978 authored by Brendan Jackman's avatar Brendan Jackman Committed by Joel Fernandes
Browse files

sched/core: Warn if ENERGY_AWARE is enabled but data is missing 



If the EAS energy model is missing or incomplete, i.e. sd_scs is NULL, then
sched_group_energy will return -EINVAL on the assumption that it raced with a
CPU hotplug event. In that case, energy_diff will return 0 and the energy-aware
wake path will silently fail to trigger any migrations.

This case can be triggered by disabling CONFIG_SCHED_MC on existing platforms,
so that there are no sched_groups with the SD_SHARE_CAP_STATES flag, so that
sd_scs is NULL.

Add checks so that a warning is printed if EAS is ever enabled while the
necessary data is not present.

Change-Id: Id233a510b5ad8b7fcecac0b1d789e730bbfc7c4a
Signed-off-by: default avatarBrendan Jackman <brendan.jackman@arm.com>
parent e79f447a

kernel/sched/core.c

+22 −0
Original line number Diff line number Diff line
@@ -91,6 +91,8 @@ 
#include <trace/events/sched.h>

#include "walt.h"



static bool have_sched_energy_data(void);



DEFINE_MUTEX(sched_domains_mutex);

DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
@@ -193,6 +195,10 @@ static int sched_feat_set(char *cmp) 
				sysctl_sched_features &= ~(1UL << i);

				sched_feat_disable(i);

			} else {

				if (i == __SCHED_FEAT_ENERGY_AWARE)

					WARN(!have_sched_energy_data(),

					     "Missing sched energy data\n");



				sysctl_sched_features |= (1UL << i);

				sched_feat_enable(i);

			}
@@ -6649,6 +6655,19 @@ static void init_sched_groups_capacity(int cpu, struct sched_domain *sd) 
	atomic_set(&sg->sgc->nr_busy_cpus, sg->group_weight);

}



static bool have_sched_energy_data(void)

{

	int cpu;



	for_each_possible_cpu(cpu) {

		if (!rcu_dereference(per_cpu(sd_scs, cpu)) ||

		    !rcu_dereference(per_cpu(sd_ea, cpu)))

			return false;

	}



	return true;

}



/*

 * Check that the per-cpu provided sd energy data is consistent for all cpus

 * within the mask.
@@ -7461,6 +7480,9 @@ static int build_sched_domains(const struct cpumask *cpu_map, 
	}

	rcu_read_unlock();



	WARN(sched_feat(ENERGY_AWARE) && !have_sched_energy_data(),

	     "Missing data for energy aware scheduling\n");



	ret = 0;

error:

	__free_domain_allocs(&d, alloc_state, cpu_map);