On 31 August 2017 at 13:58, Brendan Jackman <[email protected]> wrote: > find_idlest_group returns NULL when the local group is idlest. The > caller then continues the find_idlest_group search at a lower level > of the current CPU's sched_domain hierarchy. find_idlest_group_cpu is > not consulted and, crucially, @new_cpu is not updated. This means the > search is pointless and we return @prev_cpu from select_task_rq_fair. > > This is fixed by initialising @new_cpu to @cpu instead of > @prev_cpu. > > Signed-off-by: Brendan Jackman <[email protected]> > Cc: Dietmar Eggemann <[email protected]> > Cc: Vincent Guittot <[email protected]> > Cc: Josef Bacik <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Morten Rasmussen <[email protected]> > Cc: Peter Zijlstra <[email protected]>
Reviewed-by: Vincent Guittot <[email protected]> > --- > kernel/sched/fair.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 2608091..f93cb97 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5567,7 +5567,7 @@ find_idlest_group_cpu(struct sched_group *group, struct > task_struct *p, int this > static inline int find_idlest_cpu(struct sched_domain *sd, struct > task_struct *p, > int cpu, int prev_cpu, int sd_flag) > { > - int new_cpu = prev_cpu; > + int new_cpu = cpu; > > if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed)) > return prev_cpu; > -- > 2.7.4 >
