[PATCH v3 07/24] sched/deadline: Reset the deadline and the runtime with the parameters

[Mathieu Desnoyers]

A task that leaves SCHED_DEADLINE keeps its parameters until its 0-lag
time, so that leaving and coming back gains nothing. __dl_clear_params()
then resets them, in inactive_task_timer() or in task_non_contending(),
but leaves the deadline and the runtime of the period the task was in.

A task that comes back after its 0-lag time, and before that deadline,
is enqueued on them: enqueue_dl_entity() starts a period anew for a
task whose deadline passed, setup_new_dl_entity(), and for no other. The
task spends the runtime of the reservation it gave back before the new
one begins, and a constrained task whose deadline passed before the end
of its period is throttled on them instead, dl_check_constrained_dl()
arming the replenishment timer of the old period. The previous patch
widens the window to a period for a task that was throttled, moving its
deadline on where its timer fires outside the class.

Reset them with the parameters: the next enqueue then starts a period
from the parameters the task has.

Found by the Sashiko AI review of the second posting of this series.

Fixes: 209a0cbda7a0 ("sched/deadline: Improve the tracking of active utilization")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
---
 kernel/sched/deadline.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index d376cb493a9f..088e84fb9b10 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -3969,6 +3969,9 @@ static void __dl_clear_params(struct sched_dl_entity *dl_se)
 	dl_se->dl_bw			= 0;
 	dl_se->dl_density		= 0;
 
+	dl_se->deadline			= 0;
+	dl_se->runtime			= 0;
+
 	dl_se->dl_throttled		= 0;
 	dl_se->dl_yielded		= 0;
 	dl_se->dl_non_contending	= 0;
-- 
2.47.3