sched: Move attach_one_task and attach_task helpers to sched.h

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>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://patch.msgid.link/20260324191337.1841376-10-jstultz@google.com

2 files changed, 23 insertions, 26 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 7f35dd40d7ef..41293d5d9b75 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9947,32 +9947,6 @@ next:
 }
 
 /*
- * 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 a2629d025c90..9594355a3681 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3012,6 +3012,29 @@ 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