linux-kernel - [PATCH 2/6] sched_ext: Start schedulers with consistent p->scx.slice values

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Message-ID: <20241009214411.681233-3-tj@kernel.org>
Date: Wed,  9 Oct 2024 11:40:58 -1000
From: Tejun Heo <tj@...nel.org>
To: void@...ifault.com
Cc: kernel-team@...a.com,
	linux-kernel@...r.kernel.org,
	sched-ext@...a.com,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 2/6] sched_ext: Start schedulers with consistent p->scx.slice values

The disable path caps p->scx.slice to SCX_SLICE_DFL. As the field is already
being ignored at this stage during disable, the only effect this has is that
when the next BPF scheduler is loaded, it won't see unreasonable left-over
slices. Ultimately, this shouldn't matter but it's better to start in a
known state. Drop p->scx.slice capping from the disable path and instead
reset it to SCX_SLICE_DFL in the enable path.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 kernel/sched/ext.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index e08cfba33cb4..7d2fa78ba0c9 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4473,7 +4473,6 @@ static void scx_ops_disable_workfn(struct kthread_work *work)
 
 		sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE, &ctx);
 
-		p->scx.slice = min_t(u64, p->scx.slice, SCX_SLICE_DFL);
 		__setscheduler_prio(p, p->prio);
 		check_class_changing(task_rq(p), p, old_class);
 
@@ -5190,6 +5189,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
 
 		sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE, &ctx);
 
+		p->scx.slice = SCX_SLICE_DFL;
 		__setscheduler_prio(p, p->prio);
 		check_class_changing(task_rq(p), p, old_class);
 
-- 
2.46.2