[PATCH 3/3] sched: fix incorrect use of "ideal_runtime"s timeunit

[Stephan Baerwolf]

In "check_preempt_tick()" (kernel/sched_fair.c:1093) a ulong
called "ideal_runtime" stores a timeslice of the current task
(scheduling entity). This time complies real cpu-time.

At the end of the same function (nr_running > 1) this (real) time
is compared with a virtual-runtime-delta. Obviously the timeunits
(real vs. virtual) didn't fit.

Using "wakeup_preempt_entity()" instead should fix this in a even
more general way.

Signed-off-by: Stephan Baerwolf <stephan.baerwolf@xxxxxxxxxxxxx>
---
 kernel/sched_fair.c |   16 +++++++---------
 1 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 66dc9f7..61d002d 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1083,6 +1083,9 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 	update_cfs_shares(cfs_rq);
 }
 
+static int
+wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
+
 /*
  * Preempt the current task with a newly woken task if needed:
  */
@@ -1115,14 +1118,11 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 		return;
 
 	if (cfs_rq->nr_running > 1) {
+		// check, if maybe curr has finally overtaken the remaining leftmost
 		struct sched_entity *se = __pick_first_entity(cfs_rq);
-		s64 delta = curr->vruntime - se->vruntime;
-
-		if (delta < 0)
-			return;
-
-		if (delta > ideal_runtime)
-			resched_task(rq_of(cfs_rq)->curr);
+		
+		if (wakeup_preempt_entity(curr, se) > 0)
+		  resched_task(rq_of(cfs_rq)->curr);
 	}
 }
 
@@ -1156,8 +1156,6 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 	se->prev_sum_exec_runtime = se->sum_exec_runtime;
 }
 
-static int
-wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
 
 /*
  * Pick the next process, keeping these things in mind, in this order:
-- 
1.7.3.4


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