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

[Tejun Heo]

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@xxxxxxxxxxxxxxx # v6.12+
Reported-by: Chris Mason <clm@xxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
 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