Merge tag 'sched_ext-for-7.1-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext fixes from Tejun Heo:
 "Two low-risk fixes:

   - Drop a spurious warning that can fire during cgroup migration while
     a sched_ext scheduler is loaded

   - Fix a drgn-based debug script that broke after scheduler state
     moved into a per-scheduler struct"

* tag 'sched_ext-for-7.1-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
  sched_ext: Don't warn on NULL cgrp_moving_from in scx_cgroup_move_task()
  tools/sched_ext: Fix scx_show_state per-scheduler state reads

1 files changed, 6 insertions, 4 deletions

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 65631e577ee9..5d2d19473a82 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4402,11 +4402,13 @@ void scx_cgroup_move_task(struct task_struct *p)
 		return;
 
 	/*
-	 * @p must have ops.cgroup_prep_move() called on it and thus
-	 * cgrp_moving_from set.
+	 * scx_cgroup_can_attach() sets cgrp_moving_from only when the task's
+	 * cgroup changes. Migration keys off css rather than cgroup identity,
+	 * so it can hand an unchanged-cgroup task here with cgrp_moving_from
+	 * NULL. Nothing to report to the BPF scheduler then, so skip it and
+	 * keep prep_move and move paired.
 	 */
-	if (SCX_HAS_OP(sch, cgroup_move) &&
-	    !WARN_ON_ONCE(!p->scx.cgrp_moving_from))
+	if (SCX_HAS_OP(sch, cgroup_move) && p->scx.cgrp_moving_from)
 		SCX_CALL_OP_TASK(sch, cgroup_move, task_rq(p),
 				 p, p->scx.cgrp_moving_from,
 				 tg_cgrp(task_group(p)));