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SubjectRe: [PATCH 05/16] sched: add an rq migration call-back to sched_class
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On Wed, 27 Jun 2012 19:24:14 -0700, Paul Turner wrote:
> Since we are now doing bottom up load accumulation we need explicit
> notification when a task has been re-parented so that the old hierarchy can be
> updated.
>
> Adds task_migrate_rq(struct rq *prev, struct *rq new_rq);

It should be:
migrate_task_rq(struct task_struct *p, int next_cpu);


>
> (The alternative is to do this out of __set_task_cpu, but it was suggested that
> this would be a cleaner encapsulation.)
>
> Signed-off-by: Paul Turner <pjt@google.com>
> ---
> include/linux/sched.h | 1 +
> kernel/sched/core.c | 2 ++
> kernel/sched/fair.c | 12 ++++++++++++
> 3 files changed, 15 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 842c4df..fdfdfab 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1102,6 +1102,7 @@ struct sched_class {
>
> #ifdef CONFIG_SMP
> int (*select_task_rq)(struct task_struct *p, int sd_flag, int flags);
> + void (*migrate_task_rq)(struct task_struct *p, int next_cpu);
>
> void (*pre_schedule) (struct rq *this_rq, struct task_struct *task);
> void (*post_schedule) (struct rq *this_rq);
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index aeb8e56..c3686eb 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1109,6 +1109,8 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
> trace_sched_migrate_task(p, new_cpu);
>
> if (task_cpu(p) != new_cpu) {
> + if (p->sched_class->migrate_task_rq)
> + p->sched_class->migrate_task_rq(p, new_cpu);
> p->se.nr_migrations++;
> perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS, 1, NULL, 0);
> }
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 6200d20..33f582a 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3089,6 +3089,17 @@ unlock:
>
> return new_cpu;
> }
> +
> +/*
> + * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
> + * cfs_rq_of(p) references at time of call are still valid and identify the
> + * previous cpu. However, the caller only guarantees p->pi_lock is held; no
> + * other assumptions, including rq->lock state, should be made.
> + * Caller guarantees p->pi_lock held, but nothing else.

Duplicate sentence?


> + */
> +static void
> +migrate_task_rq_fair(struct task_struct *p, int next_cpu) {

The opening brace should start on the next line.

Thanks,
Namhyung

> +}
> #endif /* CONFIG_SMP */
>
> static unsigned long
> @@ -5754,6 +5765,7 @@ const struct sched_class fair_sched_class = {
>
> #ifdef CONFIG_SMP
> .select_task_rq = select_task_rq_fair,
> + .migrate_task_rq = migrate_task_rq_fair,
>
> .rq_online = rq_online_fair,
> .rq_offline = rq_offline_fair,


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