[PATCH v26 07/10] sched: Add assert_balance_callbacks_empty helper

John Stultz
2026-03-24T19:13:52Z

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@infradead.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: John Stultz <jstultz@google.com>
---
v24:
* Use IS_ENABLED() as suggested by K Prateek

Cc: Joel Fernandes <joelagnelf@nvidia.com>
Cc: Qais Yousef <qyousef@layalina.io>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Zimuzo Ezeozue <zezeozue@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Metin Kaya <Metin.Kaya@arm.com>
Cc: Xuewen Yan <xuewen.yan94@gmail.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: kuyo chang <kuyo.chang@mediatek.com>
Cc: hupu <hupu.gm@gmail.com>
Cc: kernel-team@android.com
---
kernel/sched/core.c | 1 +
kernel/sched/sched.h | 9 ++++++++-
2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index aa2e7287235e3..b316b6015ffea 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6856,6 +6856,7 @@ static void __sched notrace __schedule(int sched_mode)
}

pick_again:
+ assert_balance_callbacks_empty(rq);
next = pick_next_task(rq, rq->donor, &rf);
rq->next_class = next->sched_class;
if (sched_proxy_exec()) {
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 43bbf0693cca4..2a0236d745832 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1853,6 +1853,13 @@ 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 */

+static inline void assert_balance_callbacks_empty(struct rq *rq)
+{
+ WARN_ON_ONCE(IS_ENABLED(CONFIG_PROVE_LOCKING) &&
+ rq->balance_callback &&
+ rq->balance_callback != &balance_push_callback);
+}
+
/*
* Lockdep annotation that avoids accidental unlocks; it's like a
* sticky/continuous lockdep_assert_held().
@@ -1869,7 +1876,7 @@ 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)
--
2.53.0.1018.g2bb0e51243-goog