linux-kernel - [PATCH 30/46] sched_ext: Make scx_prio

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Message-ID: <20250920005931.2753828-31-tj@kernel.org>
Date: Fri, 19 Sep 2025 14:58:53 -1000
From: Tejun Heo <tj@...nel.org>
To: void@...ifault.com,
	arighi@...dia.com,
	multics69@...il.com
Cc: linux-kernel@...r.kernel.org,
	sched-ext@...ts.linux.dev,
	memxor@...il.com,
	bpf@...r.kernel.org,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 30/46] sched_ext: Make scx_prio_less() handle multiple schedulers

Call ops.core_sched_before() iff both tasks belong to the same scx_sched.
Otherwise, use timestamp based ordering.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 kernel/sched/ext.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 5b02903ba3bb..2b8a1a950c74 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -2602,16 +2602,17 @@ static struct task_struct *pick_task_scx(struct rq *rq)
 bool scx_prio_less(const struct task_struct *a, const struct task_struct *b,
 		   bool in_fi)
 {
-	struct scx_sched *sch = scx_root;
+	struct scx_sched *sch_a = scx_task_sched(a);
+	struct scx_sched *sch_b = scx_task_sched(b);
 
 	/*
 	 * The const qualifiers are dropped from task_struct pointers when
 	 * calling ops.core_sched_before(). Accesses are controlled by the
 	 * verifier.
 	 */
-	if (SCX_HAS_OP(sch, core_sched_before) &&
+	if (sch_a == sch_b && SCX_HAS_OP(sch_a, core_sched_before) &&
 	    !scx_rq_bypassing(task_rq(a)))
-		return SCX_CALL_OP_2TASKS_RET(sch, SCX_KF_REST, core_sched_before,
+		return SCX_CALL_OP_2TASKS_RET(sch_a, SCX_KF_REST, core_sched_before,
 					      NULL,
 					      (struct task_struct *)a,
 					      (struct task_struct *)b);
-- 
2.51.0