sched: Add move_queued_task_locked helper

Switch logic that deactivates, sets the task cpu,
and reactivates a task on a different rq to use a
helper that will be later extended to push entire
blocked task chains.

This patch was broken out from a larger chain migration
patch originally by Connor O'Brien.

[jstultz: split out from larger chain migration patch]
Signed-off-by: Connor O'Brien <connoro@google.com>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Metin Kaya <metin.kaya@arm.com>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Qais Yousef <qyousef@layalina.io>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: Metin Kaya <metin.kaya@arm.com>
Link: https://lore.kernel.org/r/20241009235352.1614323-5-jstultz@google.com

4 files changed, 19 insertions, 22 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f5ec452e2c5e..ab0b775a292d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2620,9 +2620,7 @@ int push_cpu_stop(void *arg)
 
 	// XXX validate p is still the highest prio task
 	if (task_rq(p) == rq) {
-		deactivate_task(rq, p, 0);
-		set_task_cpu(p, lowest_rq->cpu);
-		activate_task(lowest_rq, p, 0);
+		move_queued_task_locked(rq, lowest_rq, p);
 		resched_curr(lowest_rq);
 	}
 
@@ -3309,9 +3307,7 @@ static void __migrate_swap_task(struct task_struct *p, int cpu)
 		rq_pin_lock(src_rq, &srf);
 		rq_pin_lock(dst_rq, &drf);
 
-		deactivate_task(src_rq, p, 0);
-		set_task_cpu(p, cpu);
-		activate_task(dst_rq, p, 0);
+		move_queued_task_locked(src_rq, dst_rq, p);
 		wakeup_preempt(dst_rq, p, 0);
 
 		rq_unpin_lock(dst_rq, &drf);
@@ -6300,10 +6296,7 @@ static bool try_steal_cookie(int this, int that)
 		if (sched_task_is_throttled(p, this))
 			goto next;
 
-		deactivate_task(src, p, 0);
-		set_task_cpu(p, this);
-		activate_task(dst, p, 0);
-
+		move_queued_task_locked(src, dst, p);
 		resched_curr(dst);
 
 		success = true;
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index be1b917dc8ce..4acf5e3a5005 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2751,9 +2751,7 @@ retry:
 		goto retry;
 	}
 
-	deactivate_task(rq, next_task, 0);
-	set_task_cpu(next_task, later_rq->cpu);
-	activate_task(later_rq, next_task, 0);
+	move_queued_task_locked(rq, later_rq, next_task);
 	ret = 1;
 
 	resched_curr(later_rq);
@@ -2839,9 +2837,7 @@ static void pull_dl_task(struct rq *this_rq)
 			if (is_migration_disabled(p)) {
 				push_task = get_push_task(src_rq);
 			} else {
-				deactivate_task(src_rq, p, 0);
-				set_task_cpu(p, this_cpu);
-				activate_task(this_rq, p, 0);
+				move_queued_task_locked(src_rq, this_rq, p);
 				dmin = p->dl.deadline;
 				resched = true;
 			}
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 172c588de542..e2506ab33c97 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2088,9 +2088,7 @@ retry:
 		goto retry;
 	}
 
-	deactivate_task(rq, next_task, 0);
-	set_task_cpu(next_task, lowest_rq->cpu);
-	activate_task(lowest_rq, next_task, 0);
+	move_queued_task_locked(rq, lowest_rq, next_task);
 	resched_curr(lowest_rq);
 	ret = 1;
 
@@ -2361,9 +2359,7 @@ static void pull_rt_task(struct rq *this_rq)
 			if (is_migration_disabled(p)) {
 				push_task = get_push_task(src_rq);
 			} else {
-				deactivate_task(src_rq, p, 0);
-				set_task_cpu(p, this_cpu);
-				activate_task(this_rq, p, 0);
+				move_queued_task_locked(src_rq, this_rq, p);
 				resched = true;
 			}
 			/*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 20b6e75604ec..71ce1b05ac94 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3788,6 +3788,18 @@ static inline void init_sched_mm_cid(struct task_struct *t) { }
 
 extern u64 avg_vruntime(struct cfs_rq *cfs_rq);
 extern int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se);
+#ifdef CONFIG_SMP
+static inline
+void move_queued_task_locked(struct rq *src_rq, struct rq *dst_rq, struct task_struct *task)
+{
+	lockdep_assert_rq_held(src_rq);
+	lockdep_assert_rq_held(dst_rq);
+
+	deactivate_task(src_rq, task, 0);
+	set_task_cpu(task, dst_rq->cpu);
+	activate_task(dst_rq, task, 0);
+}
+#endif
 
 #ifdef CONFIG_RT_MUTEXES