Merge tag 'sched_ext-for-6.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext updates from Tejun Heo:

 - Move C example schedulers back from the external scx repo to
   tools/sched_ext as the authoritative source. scx_userland and
   scx_pair are returning while scx_sdt (BPF arena-based task data
   management) is new. These schedulers will be dropped from the
   external repo.

 - Improve error reporting by adding scx_bpf_error() calls when DSQ
   creation fails across all in-tree schedulers

 - Avoid redundant irq_work_queue() calls in destroy_dsq() by only
   queueing when llist_add() indicates an empty list

 - Fix flaky init_enable_count selftest by properly synchronizing
   pre-forked children using a pipe instead of sleep()

* tag 'sched_ext-for-6.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
  selftests/sched_ext: Fix init_enable_count flakiness
  tools/sched_ext: Fix data header access during free in scx_sdt
  tools/sched_ext: Add error logging for dsq creation failures in remaining schedulers
  tools/sched_ext: add arena based scheduler
  tools/sched_ext: add scx_pair scheduler
  tools/sched_ext: add scx_userland scheduler
  sched_ext: Add error logging for dsq creation failures
  sched_ext: Avoid multiple irq_work_queue() calls in destroy_dsq()

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index e6bf73456176..c18e81e8ef51 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -3520,8 +3520,8 @@ static void destroy_dsq(struct scx_sched *sch, u64 dsq_id)
 	 * operations inside scheduler locks.
 	 */
 	dsq->id = SCX_DSQ_INVALID;
-	llist_add(&dsq->free_node, &dsqs_to_free);
-	irq_work_queue(&free_dsq_irq_work);
+	if (llist_add(&dsq->free_node, &dsqs_to_free))
+		irq_work_queue(&free_dsq_irq_work);
 
 out_unlock_dsq:
 	raw_spin_unlock_irqrestore(&dsq->lock, flags);