From dd0715c770f21a78dca874a5353123d283c2586d Mon Sep 17 00:00:00 2001
From: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
Date: Wed, 14 Apr 2021 13:36:58 +0200
Subject: [PATCH] kernel: timer: Adding support to CONFIG_MULTITHREADING=n

Updated timer to not touch thread/scheduler code when multithreading
is off.

Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
---
 kernel/timer.c | 42 +++++++++++++++++++++++++++++++++++++-----
 1 file changed, 37 insertions(+), 5 deletions(-)

diff --git a/kernel/timer.c b/kernel/timer.c
index 8bdff9a590d..a5c93d5ce32 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -66,6 +66,10 @@ void z_timer_expiration_handler(struct _timeout *t)
 		timer->expiry_fn(timer);
 	}
 
+	if (!IS_ENABLED(CONFIG_MULTITHREADING)) {
+		return;
+	}
+
 	thread = z_waitq_head(&timer->wait_q);
 
 	if (thread == NULL) {
@@ -96,7 +100,10 @@ void k_timer_init(struct k_timer *timer,
 	timer->stop_fn = stop_fn;
 	timer->status = 0U;
 
-	z_waitq_init(&timer->wait_q);
+	if (IS_ENABLED(CONFIG_MULTITHREADING)) {
+		z_waitq_init(&timer->wait_q);
+	}
+
 	z_init_timeout(&timer->timeout);
 	SYS_TRACING_OBJ_INIT(k_timer, timer);
 
@@ -165,11 +172,13 @@ void z_impl_k_timer_stop(struct k_timer *timer)
 		timer->stop_fn(timer);
 	}
 
-	struct k_thread *pending_thread = z_unpend1_no_timeout(&timer->wait_q);
+	if (IS_ENABLED(CONFIG_MULTITHREADING)) {
+		struct k_thread *pending_thread = z_unpend1_no_timeout(&timer->wait_q);
 
-	if (pending_thread != NULL) {
-		z_ready_thread(pending_thread);
-		z_reschedule_unlocked();
+		if (pending_thread != NULL) {
+			z_ready_thread(pending_thread);
+			z_reschedule_unlocked();
+		}
 	}
 }
 
@@ -206,6 +215,29 @@ uint32_t z_impl_k_timer_status_sync(struct k_timer *timer)
 {
 	__ASSERT(!arch_is_in_isr(), "");
 
+	if (!IS_ENABLED(CONFIG_MULTITHREADING)) {
+		uint32_t result;
+
+		do {
+			k_spinlock_key_t key = k_spin_lock(&lock);
+
+			if (!z_is_inactive_timeout(&timer->timeout)) {
+				result = *(volatile uint32_t *)&timer->status;
+				timer->status = 0U;
+				k_spin_unlock(&lock, key);
+				if (result > 0) {
+					break;
+				}
+			} else {
+				result = timer->status;
+				k_spin_unlock(&lock, key);
+				break;
+			}
+		} while (true);
+
+		return result;
+	}
+
 	k_spinlock_key_t key = k_spin_lock(&lock);
 	uint32_t result = timer->status;