Re: [PATCH v2 4/4] sched/fair: Rework/fix task_h_load()

[Kayra Cizmeci <kayracizmeci@gmail.com>]

Hi Peter,

(Fun Stuff):

> @@ -15731,6 +15766,8 @@ static int __sched_group_set_shares(stru
>  			update_load_avg(cfs_rq, se, UPDATE_TG);
>  			update_cfs_group(se);
>  		}
> +		for_each_sched_entity_bl(se, cfs_rq)
> +			update_cfs_rq_h_load(group_cfs_rq(se), se, cfs_rq);
>  		rq_unlock_irqrestore(rq, &rf);
>  	}
>

So, the code is this:
	#define for_each_sched_entity(se, cfs_rq)					\
		for (struct sched_entity *_BL = NULL;					\
		     (se) && ((cfs_rq) = cfs_rq_of(se), (cfs_rq)->backlink = _BL, true);\
		     (se) = (se)->parent, _BL = (se))
	
	#define for_each_sched_entity_bl(se, cfs_rq) \
		for (; ((se) = (cfs_rq)->backlink); (cfs_rq) = group_cfs_rq(se))


(While writing this, a suitcase tried to assassinate me by falling from top of the closet,
what follows after this part may be the symptoms of my brain-damage.)

Let's say we have a *thing* like this:

  +----+    +----+    +------+
  |se_a| -> |rq_a| -> |task_a|
  +----+    +----+    +------+
     |
     |
     |
     V
  +----+    +----+     +------+
  |se_b| -> |rq_b|  -> |task_b|
  +----+    +----+     +------+

When we start as task_b, everything goes well. Both groups are updated.
On task_a too, only se_a is updated. 

But when we start as se_a root's backlink is NULL so we don't update anything.
While on se_b rq_a's backlink is NULL and update se_a but not ourselfes.

I don't think this is that of a problem tho, and
I could be missing something.

(Ultra-Fun Stuff (Maybe)):

Also, I saw you making an Assisted-by joke yesterday so... 

Assisted-by: Fingers (Typing)
Assisted-by: Luck (Born)
Assisted-by: Computer (IDK)
Assisted-by: Knowledge (Knowledge)
Assisted-by: Linux Itself (Kernel)
Assisted-by: EEVDF (I mean...)
Assisted-by: Water
Assisted-by: Energy (I don't have any ;<)
Assisted-by: Sun
Assisted-by: Universe
Assisted-by: Editor
Assisted-by: LKML
Assisted-by: LWN
Assisted-by: Music (Vibes)
Assisted-by: Heart (Broken ;<)
Assisted-by: Brain (Damaged a bit)

There could be more :p

Thanks,
Kayra