linux-kernel - [PATCH v23 4/9] sched: Add assert_balance_callbacks

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Message-ID: <20251030001857.681432-5-jstultz@google.com>
Date: Thu, 30 Oct 2025 00:18:45 +0000
From: John Stultz <jstultz@...gle.com>
To: LKML <linux-kernel@...r.kernel.org>
Cc: John Stultz <jstultz@...gle.com>, Peter Zijlstra <peterz@...radead.org>, 
	Joel Fernandes <joelagnelf@...dia.com>, Qais Yousef <qyousef@...alina.io>, 
	Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>, 
	Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, 
	Valentin Schneider <vschneid@...hat.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Ben Segall <bsegall@...gle.com>, Zimuzo Ezeozue <zezeozue@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Metin Kaya <Metin.Kaya@....com>, 
	Xuewen Yan <xuewen.yan94@...il.com>, K Prateek Nayak <kprateek.nayak@....com>, 
	Thomas Gleixner <tglx@...utronix.de>, Daniel Lezcano <daniel.lezcano@...aro.org>, 
	Suleiman Souhlal <suleiman@...gle.com>, kuyo chang <kuyo.chang@...iatek.com>, hupu <hupu.gm@...il.com>, 
	kernel-team@...roid.com
Subject: [PATCH v23 4/9] sched: Add assert_balance_callbacks_empty helper

With proxy-exec utilizing pick-again logic, we can end up having
balance callbacks set by the preivous pick_next_task() call left
on the list.

So pull the warning out into a helper function, and make sure we
check it when we pick again.

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: John Stultz <jstultz@...gle.com>
---
Cc: Joel Fernandes <joelagnelf@...dia.com>
Cc: Qais Yousef <qyousef@...alina.io>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Valentin Schneider <vschneid@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Ben Segall <bsegall@...gle.com>
Cc: Zimuzo Ezeozue <zezeozue@...gle.com>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Will Deacon <will@...nel.org>
Cc: Waiman Long <longman@...hat.com>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: "Paul E. McKenney" <paulmck@...nel.org>
Cc: Metin Kaya <Metin.Kaya@....com>
Cc: Xuewen Yan <xuewen.yan94@...il.com>
Cc: K Prateek Nayak <kprateek.nayak@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Suleiman Souhlal <suleiman@...gle.com>
Cc: kuyo chang <kuyo.chang@...iatek.com>
Cc: hupu <hupu.gm@...il.com>
Cc: kernel-team@...roid.com
---
 kernel/sched/core.c  |  1 +
 kernel/sched/sched.h | 11 ++++++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index da6dd2fc8e705..680ff147d270d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6896,6 +6896,7 @@ static void __sched notrace __schedule(int sched_mode)
 	}
 
 pick_again:
+	assert_balance_callbacks_empty(rq);
 	next = pick_next_task(rq, rq->donor, &rf);
 	rq_set_donor(rq, next);
 	if (unlikely(task_is_blocked(next))) {
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 361f9101cef97..de77b3313ab18 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1779,6 +1779,15 @@ static inline void scx_rq_clock_update(struct rq *rq, u64 clock) {}
 static inline void scx_rq_clock_invalidate(struct rq *rq) {}
 #endif /* !CONFIG_SCHED_CLASS_EXT */
 
+#ifdef CONFIG_PROVE_LOCKING
+static inline void assert_balance_callbacks_empty(struct rq *rq)
+{
+	WARN_ON_ONCE(rq->balance_callback && rq->balance_callback != &balance_push_callback);
+}
+#else
+static inline void assert_balance_callbacks_empty(struct rq *rq) {}
+#endif
+
 /*
  * Lockdep annotation that avoids accidental unlocks; it's like a
  * sticky/continuous lockdep_assert_held().
@@ -1795,7 +1804,7 @@ static inline void rq_pin_lock(struct rq *rq, struct rq_flags *rf)
 
 	rq->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP);
 	rf->clock_update_flags = 0;
-	WARN_ON_ONCE(rq->balance_callback && rq->balance_callback != &balance_push_callback);
+	assert_balance_callbacks_empty(rq);
 }
 
 static inline void rq_unpin_lock(struct rq *rq, struct rq_flags *rf)
-- 
2.51.1.930.gacf6e81ea2-goog