linux-kernel - [PATCH v3 1/3] sched_ext: Fix pnt

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Message-ID: <6ccd5ef5752d4cc1818e152f6b3458b0@honor.com>
Date: Sun, 20 Jul 2025 09:36:22 +0000
From: liuwenfang <liuwenfang@...or.com>
To: 'Tejun Heo' <tj@...nel.org>
CC: 'David Vernet' <void@...ifault.com>, 'Andrea Righi' <arighi@...dia.com>,
	'Changwoo Min' <changwoo@...lia.com>, 'Ingo Molnar' <mingo@...hat.com>,
	'Peter Zijlstra' <peterz@...radead.org>, 'Juri Lelli'
	<juri.lelli@...hat.com>, 'Vincent Guittot' <vincent.guittot@...aro.org>,
	'Dietmar Eggemann' <dietmar.eggemann@....com>, 'Steven Rostedt'
	<rostedt@...dmis.org>, 'Ben Segall' <bsegall@...gle.com>, 'Mel Gorman'
	<mgorman@...e.de>, 'Valentin Schneider' <vschneid@...hat.com>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>
Subject: [PATCH v3 1/3] sched_ext: Fix pnt_seq calculation

Fix pnt_seq calculation for all transitions.

Signed-off-by: Wenfang Liu liuwenfang@...or.com
---
 kernel/sched/ext.c   | 23 ++++++++++++++---------
 kernel/sched/fair.c  |  3 +++
 kernel/sched/sched.h |  8 ++++++++
 3 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index f5133249f..93e03b7d0 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -3191,14 +3191,6 @@ static void switch_class(struct rq *rq, struct task_struct *next)
 {
 	const struct sched_class *next_class = next->sched_class;
 
-#ifdef CONFIG_SMP
-	/*
-	 * Pairs with the smp_load_acquire() issued by a CPU in
-	 * kick_cpus_irq_workfn() who is waiting for this CPU to perform a
-	 * resched.
-	 */
-	smp_store_release(&rq->scx.pnt_seq, rq->scx.pnt_seq + 1);
-#endif
 	if (!static_branch_unlikely(&scx_ops_cpu_preempt))
 		return;
 
@@ -3233,6 +3225,19 @@ static void switch_class(struct rq *rq, struct task_struct *next)
 	}
 }
 
+void scx_put_prev_set_next(struct rq *rq, struct task_struct *prev,
+			   struct task_struct *next)
+{
+#ifdef CONFIG_SMP
+	/*
+	 * Pairs with the smp_load_acquire() issued by a CPU in
+	 * kick_cpus_irq_workfn() who is waiting for this CPU to perform a
+	 * resched.
+	 */
+	smp_store_release(&rq->scx.pnt_seq, rq->scx.pnt_seq + 1);
+#endif
+}
+
 static void put_prev_task_scx(struct rq *rq, struct task_struct *p,
 			      struct task_struct *next)
 {
@@ -5966,7 +5971,7 @@ static void kick_cpus_irq_workfn(struct irq_work *irq_work)
 		if (cpu != cpu_of(this_rq)) {
 			/*
 			 * Pairs with smp_store_release() issued by this CPU in
-			 * switch_class() on the resched path.
+			 * scx_put_prev_set_next() on the resched path.
 			 *
 			 * We busy-wait here to guarantee that no other task can
 			 * be scheduled on our core before the target CPU has
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0fb9bf995..50d757e92 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8887,6 +8887,9 @@ pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf
 
 	__put_prev_set_next_dl_server(rq, prev, p);
 
+	if (scx_enabled())
+		scx_put_prev_set_next(rq, prev, p);
+
 	/*
 	 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
 	 * likely that a next task is from the same cgroup as the current.
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 47972f34e..bcb7f175c 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1738,12 +1738,17 @@ static inline void scx_rq_clock_invalidate(struct rq *rq)
 	WRITE_ONCE(rq->scx.flags, rq->scx.flags & ~SCX_RQ_CLK_VALID);
 }
 
+void scx_put_prev_set_next(struct rq *rq, struct task_struct *prev,
+			   struct task_struct *next);
 #else /* !CONFIG_SCHED_CLASS_EXT */
 #define scx_enabled()		false
 #define scx_switched_all()	false
 
 static inline void scx_rq_clock_update(struct rq *rq, u64 clock) {}
 static inline void scx_rq_clock_invalidate(struct rq *rq) {}
+static inline void scx_put_prev_set_next(struct rq *rq,
+					 struct task_struct *prev,
+					 struct task_struct *next) {}
 #endif /* !CONFIG_SCHED_CLASS_EXT */
 
 /*
@@ -2465,6 +2470,9 @@ static inline void put_prev_set_next_task(struct rq *rq,
 
 	__put_prev_set_next_dl_server(rq, prev, next);
 
+	if (scx_enabled())
+		scx_put_prev_set_next(rq, prev, next);
+
 	if (next == prev)
 		return;
 
-- 
2.17.1