[PATCH v26 09/10] sched: Move attach_one_task and attach_task helpers to sched.h

John Stultz
2026-03-24T19:13:55Z

The fair scheduler locally introduced attach_one_task() and
attach_task() helpers, but these could be generically useful so
move this code to sched.h so we can use them elsewhere.

One minor tweak made to utilize guard(rq_lock)(rq) to simplifiy
the function.

Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: John Stultz <jstultz@google.com>
---
v26:
* Folded in switch to use guard(rq_lock)(rq) 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/fair.c | 26 --------------------------
kernel/sched/sched.h | 23 +++++++++++++++++++++++
2 files changed, 23 insertions(+), 26 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bf948db905ed1..53da01a251487 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9784,32 +9784,6 @@ static int detach_tasks(struct lb_env *env)
return detached;
}

-/*
- * attach_task() -- attach the task detached by detach_task() to its new rq.
- */
-static void attach_task(struct rq *rq, struct task_struct *p)
-{
- lockdep_assert_rq_held(rq);
-
- WARN_ON_ONCE(task_rq(p) != rq);
- activate_task(rq, p, ENQUEUE_NOCLOCK);
- wakeup_preempt(rq, p, 0);
-}
-
-/*
- * attach_one_task() -- attaches the task returned from detach_one_task() to
- * its new rq.
- */
-static void attach_one_task(struct rq *rq, struct task_struct *p)
-{
- struct rq_flags rf;
-
- rq_lock(rq, &rf);
- update_rq_clock(rq);
- attach_task(rq, p);
- rq_unlock(rq, &rf);
-}
-
/*
* attach_tasks() -- attaches all tasks detached by detach_tasks() to their
* new rq.
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 2a0236d745832..d4def70df05a6 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3008,6 +3008,29 @@ extern void deactivate_task(struct rq *rq, struct task_struct *p, int flags);

extern void wakeup_preempt(struct rq *rq, struct task_struct *p, int flags);

+/*
+ * attach_task() -- attach the task detached by detach_task() to its new rq.
+ */
+static inline void attach_task(struct rq *rq, struct task_struct *p)
+{
+ lockdep_assert_rq_held(rq);
+
+ WARN_ON_ONCE(task_rq(p) != rq);
+ activate_task(rq, p, ENQUEUE_NOCLOCK);
+ wakeup_preempt(rq, p, 0);
+}
+
+/*
+ * attach_one_task() -- attaches the task returned from detach_one_task() to
+ * its new rq.
+ */
+static inline void attach_one_task(struct rq *rq, struct task_struct *p)
+{
+ guard(rq_lock)(rq);
+ update_rq_clock(rq);
+ attach_task(rq, p);
+}
+
#ifdef CONFIG_PREEMPT_RT
# define SCHED_NR_MIGRATE_BREAK 8
#else
--
2.53.0.1018.g2bb0e51243-goog