FAILED: patch "[PATCH] sched_ext: Pass held rq to SCX_CALL_OP() for" failed to apply to 6.18-stable tree

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 4155fb489fa175ec74eedde7d02219cf2fe74303
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026051216-garage-angles-0119@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 4155fb489fa175ec74eedde7d02219cf2fe74303 Mon Sep 17 00:00:00 2001
From: Tejun Heo <[email protected]>
Date: Fri, 24 Apr 2026 14:31:36 -1000
Subject: [PATCH] sched_ext: Pass held rq to SCX_CALL_OP() for
core_sched_before

scx_prio_less() runs from core-sched's pick_next_task() path with rq locked but invokes ops.core_sched_before() with NULL locked_rq, leaving scx_locked_rq_state NULL. If the BPF callback calls a kfunc that re-acquires rq based on scx_locked_rq() - e.g. scx_bpf_cpuperf_set(cpu)
- it re-acquires the already-held rq.

Pass task_rq(a).

index 73d629559d6d..ba977154273c 100644
@@ -3198,7 +3198,7 @@ bool scx_prio_less(const struct task_struct *a, const struct task_struct *b,
 	if (sch_a == sch_b && SCX_HAS_OP(sch_a, core_sched_before) &&
 	    !scx_bypassing(sch_a, task_cpu(a)))
 		return SCX_CALL_OP_2TASKS_RET(sch_a, core_sched_before,
-					      NULL,
+					      task_rq(a),
 					      (struct task_struct *)a,
 					      (struct task_struct *)b);
 	else

From: Tejun Heo <[email protected]>

[ Upstream commit 4155fb489fa175ec74eedde7d02219cf2fe74303 ]

scx_prio_less() runs from core-sched's pick_next_task() path with rq locked but invokes ops.core_sched_before() with NULL locked_rq, leaving scx_locked_rq_state NULL. If the BPF callback calls a kfunc that re-acquires rq based on scx_locked_rq() - e.g. scx_bpf_cpuperf_set(cpu)
- it re-acquires the already-held rq.

Pass task_rq(a).

---
 kernel/sched/ext.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 177bbf31116d0..29d3663fe4dcf 100644
@@ -2522,7 +2522,7 @@ bool scx_prio_less(const struct task_struct *a, const struct task_struct *b,
 	if (SCX_HAS_OP(sch, core_sched_before) &&
 	    !scx_rq_bypassing(task_rq(a)))
 		return SCX_CALL_OP_2TASKS_RET(sch, SCX_KF_REST, core_sched_before,
-					      NULL,
+					      task_rq(a),
 					      (struct task_struct *)a,
 					      (struct task_struct *)b);
 	else

2.53.0