[PATCH 10/13] sched_ext: Pass held rq to SCX_CALL_OP() for core_sched_before

[Tejun Heo <tj@kernel.org>]

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).

Fixes: 7b0888b7cc19 ("sched_ext: Implement core-sched support")
Cc: stable@vger.kernel.org # v6.12+
Reported-by: Chris Mason <clm@meta.com>
Signed-off-by: Tejun Heo <tj@kernel.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 90008be04c7c..da188af21b3d 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -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
-- 
2.53.0