On Fri, Feb 19, 2016 at 01:43:45PM +0100, luca abeni wrote:
> Hi,
>
> when playing with the __dl_{add,sub}_ac() stuff recently posted by
> Juri, I found something that looks strange in prio_changed_dl():
>
> static void prio_changed_dl(struct rq *rq, struct task_struct *p,
> int oldprio)
> {
> if (task_on_rq_queued(p) || rq->curr == p) {
> [...]
> } else
> switched_to_dl(rq, p);
> }
> but switched_to_dl() does:
> static void switched_to_dl(struct rq *rq, struct task_struct *p)
> {
> if (task_on_rq_queued(p) && rq->curr != p) {
> [...]
> }
> }
>
> so, prio_changed_dl() invokes switched_to_dl() if task_on_rq_queued()
> is false, but in this case switched_to_dl() does nothing... Am I
> missing something, or the
> } else
> switched_to_dl(rq, p);
> is useless?
Agreed, see below.
> (BTW, it seems to me that switched_to_dl() is never invoked, for some
> reason...)
Hmm, it should be invoked if you do sched_setattr() to get
SCHED_DEADLINE.
---
Subject: sched/deadline: Remove superfluous call to switched_to_dl()
if (A || B) {
} else if (A && !B) {
}
If A we'll take the first branch, if !A we will not satisfy the second.
Therefore the second branch will never be taken.
Cc: Juri Lelli <juri.le...@arm.com>
Reported-by: luca abeni <luca.ab...@unitn.it>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
kernel/sched/deadline.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 57b939c81bce..c161c53d9424 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1768,8 +1768,7 @@ static void prio_changed_dl(struct rq *rq, struct
task_struct *p,
*/
resched_curr(rq);
#endif /* CONFIG_SMP */
- } else
- switched_to_dl(rq, p);
+ }
}
const struct sched_class dl_sched_class = {
