[PATCH 09/13] sched_ext: Pass held rq to SCX_CALL_OP() for dump_cpu/dump_task

Tejun Heo
2026-04-24T20:44:29Z

scx_dump_state() walks CPUs with rq_lock_irqsave() held and invokes
ops.dump_cpu / ops.dump_task 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 the held rq to SCX_CALL_OP(). Thread it into scx_dump_task() too.
The pre-loop ops.dump call runs before rq_lock_irqsave() so keeps
rq=NULL.

Fixes: 07814a9439a3 ("sched_ext: Print debug dump after an error exit")
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 | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 608d5dc4c8bc..90008be04c7c 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -6096,9 +6096,8 @@ static void ops_dump_exit(void)
scx_dump_data.cpu = -1;
}

-static void scx_dump_task(struct scx_sched *sch,
- struct seq_buf *s, struct scx_dump_ctx *dctx,
- struct task_struct *p, char marker)
+static void scx_dump_task(struct scx_sched *sch, struct seq_buf *s, struct scx_dump_ctx *dctx,
+ struct rq *rq, struct task_struct *p, char marker)
{
static unsigned long bt[SCX_EXIT_BT_LEN];
struct scx_sched *task_sch = scx_task_sched(p);
@@ -6139,7 +6138,7 @@ static void scx_dump_task(struct scx_sched *sch,

if (SCX_HAS_OP(sch, dump_task)) {
ops_dump_init(s, " ");
- SCX_CALL_OP(sch, dump_task, NULL, dctx, p);
+ SCX_CALL_OP(sch, dump_task, rq, dctx, p);
ops_dump_exit();
}

@@ -6263,8 +6262,7 @@ static void scx_dump_state(struct scx_sched *sch, struct scx_exit_info *ei,
used = seq_buf_used(&ns);
if (SCX_HAS_OP(sch, dump_cpu)) {
ops_dump_init(&ns, " ");
- SCX_CALL_OP(sch, dump_cpu, NULL,
- &dctx, cpu, idle);
+ SCX_CALL_OP(sch, dump_cpu, rq, &dctx, cpu, idle);
ops_dump_exit();
}

@@ -6287,11 +6285,11 @@ static void scx_dump_state(struct scx_sched *sch, struct scx_exit_info *ei,

if (rq->curr->sched_class == &ext_sched_class &&
(dump_all_tasks || scx_task_on_sched(sch, rq->curr)))
- scx_dump_task(sch, &s, &dctx, rq->curr, '*');
+ scx_dump_task(sch, &s, &dctx, rq, rq->curr, '*');

list_for_each_entry(p, &rq->scx.runnable_list, scx.runnable_node)
if (dump_all_tasks || scx_task_on_sched(sch, p))
- scx_dump_task(sch, &s, &dctx, p, ' ');
+ scx_dump_task(sch, &s, &dctx, rq, p, ' ');
next:
rq_unlock_irqrestore(rq, &rf);
}
--
2.53.0