sched/fair: ignore backup CPU when not valid
The find_best_target can sometimes not return a valid backup CPU, either
because it cannot find one or just becasue it returns prev_cpu as a backup.
In these cases we should skip the energy_diff evaluation for the backup CPU.
Change-Id: I3787dbdfe74122348dd7a7485b88c4679051bd32
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
(cherry picked from commit d9bcf5b88594a0225b51878236e49305f272eadc)
[trivial cherry-pick issue]
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index aa3d7bd..d9a2a02 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7071,7 +7071,9 @@ static int select_energy_cpu_brute(struct task_struct *p, int prev_cpu, int sync
/* No energy saving for target_cpu, try backup */
target_cpu = tmp_backup;
eenv.dst_cpu = target_cpu;
- if (tmp_backup < 0 || energy_diff(&eenv) >= 0) {
+ if (tmp_backup < 0 ||
+ tmp_backup == prev_cpu ||
+ energy_diff(&eenv) >= 0) {
schedstat_inc(p->se.statistics.nr_wakeups_secb_no_nrg_sav);
schedstat_inc(this_rq()->eas_stats.secb_no_nrg_sav);
target_cpu = prev_cpu;