diff --git a/kernel/unified/include/kernel_structs.h b/kernel/unified/include/kernel_structs.h
index e4483f77dbf..8ec5d99532f 100644
--- a/kernel/unified/include/kernel_structs.h
+++ b/kernel/unified/include/kernel_structs.h
@@ -33,11 +33,6 @@
 /* thread is defined statically */
 #define K_STATIC (1 << 8)
 
-#define K_READY 0
-
-/* Thread is waiting on a timeout */
-#define K_TIMING (1 << 12)
-
 /* Thread is waiting on an object */
 #define K_PENDING (1 << 13)
 
@@ -53,9 +48,6 @@
 /* Not a real thread */
 #define K_DUMMY (1 << 17)
 
-#define K_EXECUTION_MASK \
-	(K_TIMING | K_PENDING | K_PRESTART | K_DEAD | K_SUSPENDED | K_DUMMY)
-
 #if defined(CONFIG_FP_SHARING)
 /* thread uses floating point registers */
 #define K_FP_REGS (1 << 4)
diff --git a/kernel/unified/include/ksched.h b/kernel/unified/include/ksched.h
index 8c091eba7cd..08dab077ffa 100644
--- a/kernel/unified/include/ksched.h
+++ b/kernel/unified/include/ksched.h
@@ -258,22 +258,14 @@ static inline void _mark_thread_as_not_suspended(struct k_thread *thread)
 	thread->base.flags &= ~K_SUSPENDED;
 }
 
-/* mark a thread as being in the timer queue */
-static inline void _mark_thread_as_timing(struct k_thread *thread)
+/* check if a thread is on the timeout queue */
+static inline int _is_thread_timeout_active(struct k_thread *thread)
 {
-	thread->base.flags |= K_TIMING;
-}
-
-/* mark a thread as not being in the timer queue */
-static inline void _mark_thread_as_not_timing(struct k_thread *thread)
-{
-	thread->base.flags &= ~K_TIMING;
-}
-
-/* check if a thread is on the timer queue */
-static inline int _is_thread_timing(struct k_thread *thread)
-{
-	return !!(thread->base.flags & K_TIMING);
+#ifdef CONFIG_SYS_CLOCK_EXISTS
+	return thread->base.timeout.delta_ticks_from_prev != -1;
+#else
+	return 0;
+#endif
 }
 
 static inline int _has_thread_started(struct k_thread *thread)
@@ -281,10 +273,19 @@ static inline int _has_thread_started(struct k_thread *thread)
 	return !(thread->base.flags & K_PRESTART);
 }
 
+static inline int _is_thread_prevented_from_running(struct k_thread *thread)
+{
+	return thread->base.flags & (K_PENDING   | K_PRESTART |
+				     K_DEAD      | K_DUMMY    |
+				     K_SUSPENDED);
+
+}
+
 /* check if a thread is ready */
 static inline int _is_thread_ready(struct k_thread *thread)
 {
-	return (thread->base.flags & K_EXECUTION_MASK) == K_READY;
+	return !(_is_thread_prevented_from_running(thread) ||
+		 _is_thread_timeout_active(thread));
 }
 
 /* mark a thread as pending in its TCS */
@@ -305,11 +306,22 @@ static inline int _is_thread_pending(struct k_thread *thread)
 	return !!(thread->base.flags & K_PENDING);
 }
 
-/*
- * Mark the thread as not being in the timer queue. If this makes it ready,
- * then add it to the ready queue according to its priority.
+/**
+ * @brief Mark a thread as started
+ *
+ * This routine must be called with interrupts locked.
+ */
+static inline void _mark_thread_as_started(struct k_thread *thread)
+{
+	thread->base.flags &= ~K_PRESTART;
+}
+
+/*
+ * Put the thread in the ready queue according to its priority if it is not
+ * blocked for another reason (eg. suspended).
+ *
+ * Must be called with interrupts locked.
  */
-/* must be called with interrupts locked */
 static inline void _ready_thread(struct k_thread *thread)
 {
 	__ASSERT(_is_prio_higher(thread->base.prio, K_LOWEST_THREAD_PRIO) ||
@@ -324,24 +336,14 @@ static inline void _ready_thread(struct k_thread *thread)
 		 "thread %p prio too high (id %d, cannot be higher than %d)",
 		 thread, thread->base.prio, K_HIGHEST_THREAD_PRIO);
 
-	/* K_PRESTART is needed to handle the start-with-delay case */
-	_reset_thread_states(thread, K_TIMING|K_PRESTART);
+	/* needed to handle the start-with-delay case */
+	_mark_thread_as_started(thread);
 
 	if (_is_thread_ready(thread)) {
 		_add_thread_to_ready_q(thread);
 	}
 }
 
-/**
- * @brief Mark a thread as started
- *
- * This routine must be called with interrupts locked.
- */
-static inline void _mark_thread_as_started(struct k_thread *thread)
-{
-	thread->base.flags &= ~K_PRESTART;
-}
-
 /**
  * @brief Mark thread as dead
  *
diff --git a/kernel/unified/include/timeout_q.h b/kernel/unified/include/timeout_q.h
index bbfaea78e80..fc730918d35 100644
--- a/kernel/unified/include/timeout_q.h
+++ b/kernel/unified/include/timeout_q.h
@@ -98,6 +98,8 @@ static inline struct _timeout *_handle_one_timeout(
 	struct _timeout *t = (void *)sys_dlist_get(timeout_q);
 	struct k_thread *thread = t->thread;
 
+	t->delta_ticks_from_prev = -1;
+
 	K_DEBUG("timeout %p\n", t);
 	if (thread != NULL) {
 		_unpend_thread_timing_out(thread, t);
@@ -105,14 +107,6 @@ static inline struct _timeout *_handle_one_timeout(
 	} else if (t->func) {
 		t->func(t);
 	}
-	/*
-	 * Note: t->func() may add timeout again. Make sure that
-	 * delta_ticks_from_prev is set to -1 only if timeout is
-	 * still expired (delta_ticks_from_prev == 0)
-	 */
-	if (t->delta_ticks_from_prev == 0) {
-		t->delta_ticks_from_prev = -1;
-	}
 
 	return (struct _timeout *)sys_dlist_peek_head(timeout_q);
 }
diff --git a/kernel/unified/include/wait_q.h b/kernel/unified/include/wait_q.h
index 02d59a1e05b..41f6b644c10 100644
--- a/kernel/unified/include/wait_q.h
+++ b/kernel/unified/include/wait_q.h
@@ -34,8 +34,21 @@ static ALWAYS_INLINE void _init_thread_timeout(struct _thread_base *thread_base)
 {
 	ARG_UNUSED(thread_base);
 }
-#define _add_thread_timeout(thread, wait_q, timeout) do { } while (0)
-static inline int _abort_thread_timeout(struct k_thread *thread) { return 0; }
+
+static ALWAYS_INLINE void
+_add_thread_timeout(struct k_thread *thread, _wait_q_t *wait_q, int32_t timeout)
+{
+	ARG_UNUSED(thread);
+	ARG_UNUSED(wait_q);
+	ARG_UNUSED(timeout);
+}
+
+static ALWAYS_INLINE int _abort_thread_timeout(struct k_thread *thread)
+{
+	ARG_UNUSED(thread);
+
+	return 0;
+}
 #define _get_next_timeout_expiry() (K_FOREVER)
 #endif
 
diff --git a/kernel/unified/legacy_timer.c b/kernel/unified/legacy_timer.c
index aae48913514..d7b52895263 100644
--- a/kernel/unified/legacy_timer.c
+++ b/kernel/unified/legacy_timer.c
@@ -33,7 +33,6 @@ void _legacy_sleep(int32_t ticks)
 
 	int key = irq_lock();
 
-	_mark_thread_as_timing(_current);
 	_remove_thread_from_ready_q(_current);
 	_add_thread_timeout(_current, NULL, ticks);
 
diff --git a/kernel/unified/sched.c b/kernel/unified/sched.c
index 74090cb78c2..f0729be0fc5 100644
--- a/kernel/unified/sched.c
+++ b/kernel/unified/sched.c
@@ -168,9 +168,9 @@ void _pend_thread(struct k_thread *thread, _wait_q_t *wait_q, int32_t timeout)
 	_mark_thread_as_pending(thread);
 
 	if (timeout != K_FOREVER) {
-		_mark_thread_as_timing(thread);
-		_add_thread_timeout(thread, wait_q,
-					_TICK_ALIGN + _ms_to_ticks(timeout));
+		int32_t ticks = _TICK_ALIGN + _ms_to_ticks(timeout);
+
+		_add_thread_timeout(thread, wait_q, ticks);
 	}
 }
 
@@ -306,12 +306,11 @@ void k_sleep(int32_t duration)
 		return;
 	}
 
+	int32_t ticks = _TICK_ALIGN + _ms_to_ticks(duration);
 	int key = irq_lock();
 
-	_mark_thread_as_timing(_current);
 	_remove_thread_from_ready_q(_current);
-	_add_thread_timeout(_current, NULL,
-				_TICK_ALIGN + _ms_to_ticks(duration));
+	_add_thread_timeout(_current, NULL, ticks);
 
 	_Swap(key);
 }
diff --git a/kernel/unified/sem.c b/kernel/unified/sem.c
index 045ced996a2..ec3bc95f67b 100644
--- a/kernel/unified/sem.c
+++ b/kernel/unified/sem.c
@@ -222,8 +222,8 @@ static int handle_sem_group(struct k_sem *sem, struct k_thread *thread)
 	 */
 
 	if (!_is_thread_ready(desc->thread)) {
-		_reset_thread_states(desc->thread, K_PENDING | K_TIMING);
 		_abort_thread_timeout(desc->thread);
+		_mark_thread_as_not_pending(desc->thread);
 		if (_is_thread_ready(desc->thread)) {
 			_add_thread_to_ready_q(desc->thread);
 		}
diff --git a/kernel/unified/thread.c b/kernel/unified/thread.c
index 2d6ca1748f4..b2a14259db6 100644
--- a/kernel/unified/thread.c
+++ b/kernel/unified/thread.c
@@ -220,9 +220,9 @@ static void schedule_new_thread(struct k_thread *thread, int32_t delay)
 	if (delay == 0) {
 		start_thread(thread);
 	} else {
-		_mark_thread_as_timing(thread);
-		_add_thread_timeout(thread, NULL,
-					_TICK_ALIGN + _ms_to_ticks(delay));
+		int32_t ticks = _TICK_ALIGN + _ms_to_ticks(delay);
+
+		_add_thread_timeout(thread, NULL, ticks);
 	}
 #else
 	ARG_UNUSED(delay);
@@ -252,7 +252,8 @@ int k_thread_cancel(k_tid_t tid)
 
 	int key = irq_lock();
 
-	if (_has_thread_started(thread) || !_is_thread_timing(thread)) {
+	if (_has_thread_started(thread) ||
+	    !_is_thread_timeout_active(thread)) {
 		irq_unlock(key);
 		return -EINVAL;
 	}
@@ -365,9 +366,8 @@ void _k_thread_single_abort(struct k_thread *thread)
 		if (_is_thread_pending(thread)) {
 			_unpend_thread(thread);
 		}
-		if (_is_thread_timing(thread)) {
+		if (_is_thread_timeout_active(thread)) {
 			_abort_thread_timeout(thread);
-			_mark_thread_as_not_timing(thread);
 		}
 	}
 	_mark_thread_as_dead(thread);