Commit-ID: 6fee85ccbc76e8aeba43dc120c5fa3c5409a4e2c Gitweb: https://git.kernel.org/tip/6fee85ccbc76e8aeba43dc120c5fa3c5409a4e2c Author: Brendan Jackman <brendan.jack...@arm.com> AuthorDate: Thu, 5 Oct 2017 12:45:15 +0100 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Tue, 10 Oct 2017 11:45:35 +0200
sched/fair: Fix usage of find_idlest_group() when no groups are allowed When 'p' is not allowed on any of the CPUs in the sched_domain, we currently return NULL from find_idlest_group(), and pointlessly continue the search on lower sched_domain levels (where 'p' is also not allowed) before returning prev_cpu regardless (as we have not updated new_cpu). Add an explicit check for this case, and add a comment to find_idlest_group(). Now when find_idlest_group() returns NULL, it always means that the local group is allowed and idlest. Signed-off-by: Brendan Jackman <brendan.jack...@arm.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Reviewed-by: Vincent Guittot <vincent.guit...@linaro.org> Reviewed-by: Josef Bacik <jba...@fb.com> Cc: Dietmar Eggemann <dietmar.eggem...@arm.com> Cc: Josef Bacik <jo...@toxicpanda.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Mike Galbraith <efa...@gmx.de> Cc: Morten Rasmussen <morten.rasmus...@arm.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/20171005114516.18617-5-brendan.jack...@arm.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/sched/fair.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index cca1835..ed80d6b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5730,6 +5730,8 @@ static unsigned long capacity_spare_wake(int cpu, struct task_struct *p) /* * find_idlest_group finds and returns the least busy CPU group within the * domain. + * + * Assumes p is allowed on at least one CPU in sd. */ static struct sched_group * find_idlest_group(struct sched_domain *sd, struct task_struct *p, @@ -5917,6 +5919,9 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p { int new_cpu = prev_cpu; + if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed)) + return prev_cpu; + while (sd) { struct sched_group *group; struct sched_domain *tmp;
