Merge pull request #2541 from BernardXiong/fix_critical_smp

[Kernel] Fix the critical issue under smp

src/scheduler.c

@@ -792,6 +792,12 @@ void rt_enter_critical(void)
     level = rt_hw_local_irq_disable();
 
     current_thread = rt_cpu_self()->current_thread;
+    if (!current_thread)
+    {
+        rt_hw_local_irq_enable(level);
+        return ;
+    }
+
     /*
      * the maximal number of nest is RT_UINT16_MAX, which is big
      * enough and does not check here
@@ -842,6 +848,11 @@ void rt_exit_critical(void)
     level = rt_hw_local_irq_disable();
 
     current_thread = rt_cpu_self()->current_thread;
+    if (!current_thread)
+    {
+        rt_hw_local_irq_enable(level);
+        return ;
+    }
 
     current_thread->scheduler_lock_nest --;
 
@@ -873,14 +884,17 @@ void rt_exit_critical(void)
     level = rt_hw_interrupt_disable();
 
     rt_scheduler_lock_nest --;
-
     if (rt_scheduler_lock_nest <= 0)
     {
         rt_scheduler_lock_nest = 0;
         /* enable interrupt */
         rt_hw_interrupt_enable(level);
 
-        rt_schedule();
+        if (rt_current_thread)
+        {
+            /* if scheduler is started, do a schedule */
+            rt_schedule();
+        }
     }
     else
     {