IDLE TCB setup needs to indicate the the IDLE thread is a privileged, kernel thread

sched/init/os_start.c

@@ -300,6 +300,7 @@ void os_start(void)
   bzero((void*)&g_idletcb, sizeof(struct task_tcb_s));
   g_idletcb.cmn.task_state = TSTATE_TASK_RUNNING;
   g_idletcb.cmn.entry.main = (main_t)os_start;
+  g_idletcb.cmn.flags      = TCB_FLAG_TTYPE_KERNEL;
 
   /* Set the IDLE task name */
 

sched/task/task.h

@@ -63,15 +63,23 @@
  * Public Function Prototypes
  ****************************************************************************/
 
+/* Task start-up */
+
 void task_start(void);
 int  task_schedsetup(FAR struct task_tcb_s *tcb, int priority,
        start_t start, main_t main, uint8_t ttype);
 int  task_argsetup(FAR struct task_tcb_s *tcb, FAR const char *name,
        FAR char * const argv[]);
+
+/* Task exit */
+
 int  task_exit(void);
 int  task_terminate(pid_t pid, bool nonblocking);
 void task_exithook(FAR struct tcb_s *tcb, int status, bool nonblocking);
 void task_recover(FAR struct tcb_s *tcb);
+
+/* Misc. */
+
 bool sched_addreadytorun(FAR struct tcb_s *rtrtcb);
 
 #endif /* __SCHED_TASK_TASK_H */