On Mon, 06 Jun, at 08:20:39AM, Yuyang Du wrote:
> Newly forked task has not been enqueued, so should not be removed from
> cfs_rq in task_move_group_fair(). To do so, we need to pass the fork
> information all the way from sched_move_task() to task_move_group_fair().
>
> Signed-off-by: Yuyang Du <yuyang...@intel.com>
> ---
> kernel/sched/auto_group.c | 2 +-
> kernel/sched/core.c | 8 ++++----
> kernel/sched/fair.c | 8 ++++++--
> kernel/sched/sched.h | 4 ++--
> 4 files changed, 13 insertions(+), 9 deletions(-)
[...]
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 28b3415..370e284 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -8429,9 +8429,13 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
> }
>
> #ifdef CONFIG_FAIR_GROUP_SCHED
> -static void task_move_group_fair(struct task_struct *p)
> +static void task_move_group_fair(struct task_struct *p, bool fork)
> {
> - detach_task_cfs_rq(p);
> + /*
> + * Newly forked task should not be removed from any cfs_rq
> + */
> + if (!fork)
> + detach_task_cfs_rq(p);
> set_task_rq(p, task_cpu(p));
> attach_task_cfs_rq(p);
> /*
Wouldn't it be more symmetric to add,
if (p->se.avg.last_update_time)
__update_load_avg(...)
to detach_entity_load_avg() so that there's no need to pass the @fork
parameter all the way down the stack, and more importantly, remember
to *not* call detach_task_cfs_rq() if the code changes in the future?
Additionally adding the above check looks like it would fix a race
that (I think) occurs if a newly forked task's class is changed before
it is enqueued in wake_up_new_task().
