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Groups > linux.kernel > #1582281

[PATCH v3 1/2] sched/deadline: Remove unnecessary condition in push_dl_task()

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pick_next_pushable_dl_task(rq) has BUG_ON(rq->cpu != task_cpu(task))
when it returns a task other than NULL, which means that task_cpu(task)
must be rq->cpu. So if task == next_task, then task_cpu(next_task) must
be rq->cpu as well. Remove the redundant condition and make code simpler.

By this patch, unnecessary one branch and two LOAD operations in 'if'
statement can be avoided.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Juri Lelli <juri.lelli@arm.com>
---
 kernel/sched/deadline.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 27737f3..ad8d577 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1483,7 +1483,7 @@ static int push_dl_task(struct rq *rq)
 		 * then possible that next_task has migrated.
 		 */
 		task = pick_next_pushable_dl_task(rq);
-		if (task_cpu(next_task) == rq->cpu && task == next_task) {
+		if (task == next_task) {
 			/*
 			 * The task is still there. We don't try
 			 * again, some other cpu will pull it when ready.
-- 
1.9.1

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[PATCH v3 1/2] sched/deadline: Remove unnecessary condition in push_dl_task() Byungchul Park <byungchul.park@lge.com> - 2017-02-16 03:40 +0100
  Re: [PATCH v3 1/2] sched/deadline: Remove unnecessary condition in  push_dl_task() Daniel Bristot de Oliveira <bristot@redhat.com> - 2017-02-16 18:40 +0100
  Re: [PATCH v3 1/2] sched/deadline: Remove unnecessary condition in  push_dl_task() Byungchul Park <byungchul.park@lge.com> - 2017-02-22 06:10 +0100

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