sched/fair: Fix usage of find_idlest_group() when the local group is idlest
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 <brendan.jackman@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Josef Bacik <jbacik@fb.com> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Josef Bacik <josef@toxicpanda.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Morten Rasmussen <morten.rasmussen@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20171005114516.18617-6-brendan.jackman@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -5917,7 +5917,7 @@ find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this
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static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
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static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
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int cpu, int prev_cpu, int sd_flag)
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int cpu, int prev_cpu, int sd_flag)
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{
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{
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int new_cpu = prev_cpu;
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int new_cpu = cpu;
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if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed))
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if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed))
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return prev_cpu;
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return prev_cpu;
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