From: Andrea Righi <arighi@nvidia.com>
Date: Sat, 7 Mar 2026 09:56:31 +0000 (+0100)
Subject: sched_ext: Pass full dequeue flags to ops.quiescent()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=03f5304aad0f90907475437be8052e7e70376319;p=thirdparty%2Fkernel%2Flinux.git

sched_ext: Pass full dequeue flags to ops.quiescent()

ops.quiescent() is invoked with the same deq_flags as ops.dequeue(), so
the BPF scheduler is able to distinguish sleep vs property changes in
both callbacks.

However, dequeue_task_scx() receives deq_flags as an int from the
sched_class interface, so SCX flags above bit 32 (%SCX_DEQ_SCHED_CHANGE)
are truncated. ops_dequeue() reconstructs the full u64 for ops.dequeue(),
but ops.quiescent() is still called with the original int and can never
see %SCX_DEQ_SCHED_CHANGE.

Fix this by constructing the full u64 deq_flags in dequeue_task_scx()
(renaming the int parameter to core_deq_flags) and passing the complete
flags to both ops_dequeue() and ops.quiescent().

Fixes: ebf1ccff79c4 ("sched_ext: Fix ops.dequeue() semantics")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
---

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 72b7a87f66ec9..47f65041b363d 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -1782,14 +1782,6 @@ static void ops_dequeue(struct rq *rq, struct task_struct *p, u64 deq_flags)
 {
 	struct scx_sched *sch = scx_task_sched(p);
 	unsigned long opss;
-	u64 op_deq_flags = deq_flags;
-
-	/*
-	 * Set %SCX_DEQ_SCHED_CHANGE when the dequeue is due to a property
-	 * change (not sleep or core-sched pick).
-	 */
-	if (!(op_deq_flags & (DEQUEUE_SLEEP | SCX_DEQ_CORE_SCHED_EXEC)))
-		op_deq_flags |= SCX_DEQ_SCHED_CHANGE;
 
 	/* dequeue is always temporary, don't reset runnable_at */
 	clr_task_runnable(p, false);
@@ -1846,12 +1838,20 @@ static void ops_dequeue(struct rq *rq, struct task_struct *p, u64 deq_flags)
 	 * NONE but the task may still have %SCX_TASK_IN_CUSTODY set until
 	 * it is enqueued on the destination.
 	 */
-	call_task_dequeue(sch, rq, p, op_deq_flags);
+	call_task_dequeue(sch, rq, p, deq_flags);
 }
 
-static bool dequeue_task_scx(struct rq *rq, struct task_struct *p, int deq_flags)
+static bool dequeue_task_scx(struct rq *rq, struct task_struct *p, int core_deq_flags)
 {
 	struct scx_sched *sch = scx_task_sched(p);
+	u64 deq_flags = core_deq_flags;
+
+	/*
+	 * Set %SCX_DEQ_SCHED_CHANGE when the dequeue is due to a property
+	 * change (not sleep or core-sched pick).
+	 */
+	if (!(deq_flags & (DEQUEUE_SLEEP | SCX_DEQ_CORE_SCHED_EXEC)))
+		deq_flags |= SCX_DEQ_SCHED_CHANGE;
 
 	if (!(p->scx.flags & SCX_TASK_QUEUED)) {
 		WARN_ON_ONCE(task_runnable(p));