CFS related question

From: Cyrill Gorcunov
Date: Sat Oct 18 2008 - 16:03:45 EST

Hi Ingo, Peter,

I just curious, look we have the following

static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
struct sched_entity *se = NULL;

if (first_fair(cfs_rq)) {
se = __pick_next_entity(cfs_rq);
se = pick_next(cfs_rq, se);
set_next_entity(cfs_rq, se);

return se;

which I presume may return NULL so the following piece
could fail

static struct task_struct *pick_next_task_fair(struct rq *rq)
struct task_struct *p;
struct cfs_rq *cfs_rq = &rq->cfs;
struct sched_entity *se;

if (unlikely(!cfs_rq->nr_running))
return NULL;

do {
--> se = pick_next_entity(cfs_rq);
--> OOPs cfs_rq = group_cfs_rq(se);
} while (cfs_rq);

p = task_of(se);
hrtick_start_fair(rq, p);

return p;

Did I miss something? Or it comepletely can NOT happen?

- Cyrill -
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