diff --git a/kernel/include/ksched.h b/kernel/include/ksched.h
index 4b2c5446051..5d707056ccd 100644
--- a/kernel/include/ksched.h
+++ b/kernel/include/ksched.h
@@ -37,7 +37,6 @@ BUILD_ASSERT(K_LOWEST_APPLICATION_THREAD_PRIO
 #endif
 
 void z_sched_init(void);
-void z_add_thread_to_ready_q(struct k_thread *thread);
 void z_move_thread_to_end_of_prio_q(struct k_thread *thread);
 void z_remove_thread_from_ready_q(struct k_thread *thread);
 int z_is_thread_time_slicing(struct k_thread *thread);
@@ -61,6 +60,8 @@ void z_time_slice(int ticks);
 void z_reset_time_slice(void);
 void z_sched_abort(struct k_thread *thread);
 void z_sched_ipi(void);
+void z_sched_start(struct k_thread *thread);
+void z_ready_thread(struct k_thread *thread);
 
 static inline void z_pend_curr_unlocked(_wait_q_t *wait_q, s32_t timeout)
 {
@@ -246,14 +247,6 @@ static inline bool _is_valid_prio(int prio, void *entry_point)
 	return true;
 }
 
-static ALWAYS_INLINE void z_ready_thread(struct k_thread *thread)
-{
-	if (z_is_thread_ready(thread)) {
-		z_add_thread_to_ready_q(thread);
-		sys_trace_thread_ready(thread);
-	}
-}
-
 static inline void _ready_one_thread(_wait_q_t *wq)
 {
 	struct k_thread *thread = z_unpend_first_thread(wq);
diff --git a/kernel/sched.c b/kernel/sched.c
index 0067005b2bb..4e0bc32f32a 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -376,9 +376,10 @@ static void update_cache(int preempt_ok)
 #endif
 }
 
-void z_add_thread_to_ready_q(struct k_thread *thread)
+static void ready_thread(struct k_thread *thread)
 {
-	LOCKED(&sched_spinlock) {
+	if (z_is_thread_ready(thread)) {
+		sys_trace_thread_ready(thread);
 		_priq_run_add(&_kernel.ready_q.runq, thread);
 		z_mark_thread_as_queued(thread);
 		update_cache(0);
@@ -388,6 +389,13 @@ void z_add_thread_to_ready_q(struct k_thread *thread)
 	}
 }
 
+void z_ready_thread(struct k_thread *thread)
+{
+	LOCKED(&sched_spinlock) {
+		ready_thread(thread);
+	}
+}
+
 void z_move_thread_to_end_of_prio_q(struct k_thread *thread)
 {
 	LOCKED(&sched_spinlock) {
@@ -400,6 +408,20 @@ void z_move_thread_to_end_of_prio_q(struct k_thread *thread)
 	}
 }
 
+void z_sched_start(struct k_thread *thread)
+{
+	k_spinlock_key_t key = k_spin_lock(&sched_spinlock);
+
+	if (z_has_thread_started(thread)) {
+		k_spin_unlock(&sched_spinlock, key);
+		return;
+	}
+
+	z_mark_thread_as_started(thread);
+	ready_thread(thread);
+	z_reschedule(&sched_spinlock, key);
+}
+
 void z_thread_single_suspend(struct k_thread *thread)
 {
 	(void)z_abort_thread_timeout(thread);
diff --git a/kernel/thread.c b/kernel/thread.c
index 734879c0f2c..54f932c7a91 100644
--- a/kernel/thread.c
+++ b/kernel/thread.c
@@ -369,16 +369,7 @@ void z_check_stack_sentinel(void)
 #ifdef CONFIG_MULTITHREADING
 void z_impl_k_thread_start(struct k_thread *thread)
 {
-	k_spinlock_key_t key = k_spin_lock(&lock); /* protect kernel queues */
-
-	if (z_has_thread_started(thread)) {
-		k_spin_unlock(&lock, key);
-		return;
-	}
-
-	z_mark_thread_as_started(thread);
-	z_ready_thread(thread);
-	z_reschedule(&lock, key);
+	z_sched_start(thread);
 }
 
 #ifdef CONFIG_USERSPACE