[ulog] Fixed the problem of abnormal log output at the INIT_BOARD_EXPORT level.

components/utilities/ulog/ulog.c

@@ -190,8 +190,8 @@ static void output_unlock(void)
     if (!ulog.output_lock_enabled)
         return;
 
-    /* is in thread context */
-    if (rt_interrupt_get_nest() == 0)
+    /* If the scheduler is started and in thread context */
+    if (rt_thread_self() && (rt_interrupt_get_nest() == 0))
     {
         rt_sem_release(&ulog.output_locker);
     }
@@ -208,8 +208,8 @@ static void output_lock(void)
     if (!ulog.output_lock_enabled)
         return;
 
-    /* is in thread context */
-    if (rt_interrupt_get_nest() == 0)
+    /* If the scheduler is started and in thread context */
+    if (rt_thread_self() && (rt_interrupt_get_nest() == 0))
     {
         rt_sem_take(&ulog.output_locker, RT_WAITING_FOREVER);
     }
@@ -429,6 +429,13 @@ void ulog_output_to_all_backend(rt_uint32_t level, const char *tag, rt_bool_t is
     if (!ulog.init_ok)
         return;
 
+    /* if there is no backend */
+    if (!rt_slist_first(&ulog.backend_list))
+    {
+        rt_kputs(log);
+        return;
+    }
+
     /* output for all backends */
     for (node = rt_slist_first(&ulog.backend_list); node; node = rt_slist_next(node))
     {