serial: make ringbuf write operations atomic

kernel/ringbuf.c

@@ -31,7 +31,7 @@ size_t ringbuf_read(void *dest, struct ringbuf *buf, size_t len)
 {
 	uint8_t *tmp = dest;
 
-	while (len-- > 0 && buf->len > 0) {
+	while (len-- && buf->len) {
 		*tmp++ = buf->data[buf->rpos++];
 		buf->len--;
 
@@ -46,7 +46,7 @@ size_t ringbuf_write(struct ringbuf *buf, const void *src, size_t len)
 {
 	const uint8_t *tmp = src;
 
-	while (len-- > 0 && buf->len < buf->capacity) {
+	while (len-- && buf->len != buf->capacity) {
 		buf->data[buf->wpos++] = *tmp++;
 		buf->len++;
 

kernel/serial.c

@@ -5,6 +5,7 @@
 #include <ardix/serial.h>
 
 #include <arch/serial.h>
+#include <arch/sched.h>
 
 #include <stddef.h>
 
@@ -46,14 +47,23 @@ void serial_exit(struct serial_interface *interface)
 
 ssize_t serial_read(void *dest, struct serial_interface *interface, size_t len)
 {
-	return (ssize_t)ringbuf_read(dest, interface->rx, len);
+	ssize_t ret;
+
+	sched_atomic_enter();
+	ret = (ssize_t)ringbuf_read(dest, interface->rx, len);
+	sched_atomic_leave();
+
+	return ret;
 }
 
 ssize_t serial_write(struct serial_interface *interface, const void *data, size_t len)
 {
-	ssize_t ret = (ssize_t)ringbuf_write(interface->tx, data, len);
-	if (ret > 0)
-		arch_serial_notify(interface);
+	ssize_t ret;
+
+	sched_atomic_enter();
+	ret = (ssize_t)ringbuf_write(interface->tx, data, len);
+	sched_atomic_leave();
+
 	return ret;
 }