Messages in this thread | | | Date | Fri, 24 Oct 2014 17:32:06 +0800 | From | Wanpeng Li <> | Subject | Re: [PATCH v4 1/6] sched/fair: Fix reschedule which is generated on throttled cfs_rq |
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Hi Kirill, 10/24/14, 2:01 PM, Kirill Tkhai: > Hi, Wanpeng, > > the commit commentary confuses, I'm agree. Really it's just a cleanup. > > On Пт, 2014-10-24 at 07:27 +0800, Wanpeng Li wrote: >> Hi Kirill, >> 8/6/14, 4:06 PM, Kirill Tkhai: >>> (sched_entity::on_rq == 1) does not guarantee the task is pickable; >>> changes on throttled cfs_rq must not lead to reschedule. >> Why (sched_entity::on_rq == 1) doesn't guarantee the task is pickable >> since entity will be dequeued during throttling cfs_rq? > Because one of task's (grand)parents in hierarhy may be throtthed and > dequeued. > > But task_struct::on_rq check doesn't guarantee this too. So, just ignore > commit commentary; the commentary is wrong. > >>> Check for task_struct::on_rq instead. >> Do you mean task_struct::on_rq will be cleared during throttling cfs_rq? >> I can't find codes do this. > No, it not cleared. The commit commentary should be: > "sched: Cleanup. Check task_struct::on_rq instead of sched_entity::on_rq, > because it is the same for a task"
IIUR, for fair class, sched_entity::on_rq will be set/clear during enqueue/dequeue, task_struct::on_rq will changed during task migration, I'm not sure why they are the same.
Regards, Wanpeng Li
> > >> Regards, >> Wanpeng Li >> >>> Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> >>> --- >>> kernel/sched/fair.c | 6 +++--- >>> 1 file changed, 3 insertions(+), 3 deletions(-) >>> >>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >>> index bfa3c86..6f0ce2b 100644 >>> --- a/kernel/sched/fair.c >>> +++ b/kernel/sched/fair.c >>> @@ -7465,7 +7465,7 @@ static void task_fork_fair(struct task_struct *p) >>> static void >>> prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) >>> { >>> - if (!p->se.on_rq) >>> + if (!p->on_rq) >>> return; >>> >>> /* >>> @@ -7521,15 +7521,15 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p) >>> */ >>> static void switched_to_fair(struct rq *rq, struct task_struct *p) >>> { >>> - struct sched_entity *se = &p->se; >>> #ifdef CONFIG_FAIR_GROUP_SCHED >>> + struct sched_entity *se = &p->se; >>> /* >>> * Since the real-depth could have been changed (only FAIR >>> * class maintain depth value), reset depth properly. >>> */ >>> se->depth = se->parent ? se->parent->depth + 1 : 0; >>> #endif >>> - if (!se->on_rq) >>> + if (!p->on_rq) >>> return; >>> >>> /* >>> >>> >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> Please read the FAQ at http://www.tux.org/lkml/ >
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