[PATCH 1/3] sched: check WAKEUP_PREEMPT feature before preemting anything

[Stephan Baerwolf]

The function "check_preempt_wakeup" (kernel/sched_fair.c:1885)
will preempt idle-task (for non-idle task), even if WAKEUP_PREEMPT
is not featured (because of a too late checking the feature).
This patches moves the checking of WAKEUP_PREEMT in front of
idle-preemtion.

Signed-off-by: Stephan Baerwolf <stephan.baerwolf@xxxxxxxxxxxxx>
---
 kernel/sched_fair.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 433491c..e092e72 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1905,6 +1905,9 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
 	if (test_tsk_need_resched(curr))
 		return;
 
+	if (!sched_feat(WAKEUP_PREEMPT))
+		return;
+
 	/* Idle tasks are by definition preempted by non-idle tasks. */
 	if (unlikely(curr->policy == SCHED_IDLE) &&
 	    likely(p->policy != SCHED_IDLE))
@@ -1918,9 +1921,6 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
 		return;
 
 
-	if (!sched_feat(WAKEUP_PREEMPT))
-		return;
-
 	update_curr(cfs_rq);
 	find_matching_se(&se, &pse);
 	BUG_ON(!pse);
-- 
1.7.3.4


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