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SubjectRe: [PATCH RFC] sched/fair: fix sudden expiration of cfq quota in put_prev_task()
On Tue, Apr 07, 2015 at 02:52:51PM +0200, Peter Zijlstra wrote:
> If the above set_next_entity() is indeed the simple one, does the below
> cure things?
>
> ---
> kernel/sched/fair.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index fdae26eb7218..df72d61138a8 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5176,12 +5176,11 @@ pick_next_task_fair(struct rq *rq, struct task_struct *prev)
> simple:
> cfs_rq = &rq->cfs;
> #endif
> + put_prev_task(rq, prev);
>
> if (!cfs_rq->nr_running)
> goto idle;
>
> - put_prev_task(rq, prev);
> -
> do {
> se = pick_next_entity(cfs_rq, NULL);
> set_next_entity(cfs_rq, se);

Bah, that's broken because if we end up going idle pick_next_task_idle()
is going to do put_prev_task() again.

Lemme think a bit more on that.


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