fix lwip (#7969)

components/net/lwip/port/sys_arch.c

@@ -408,8 +408,9 @@ u32_t sys_arch_mbox_fetch(sys_mbox_t *mbox, void **msg, u32_t timeout)
         else
             t = timeout / (1000 / RT_TICK_PER_SECOND);
     }
-
-    ret = rt_mb_recv(*mbox, (rt_ubase_t *)msg, t);
+    /*When the waiting msg is generated by the application through signaling mechanisms,
+    only by using interruptible mode can the program be made runnable again*/
+    ret = rt_mb_recv_interruptibale(*mbox, (rt_ubase_t *)msg, t);
     if(ret != RT_EOK)
     {
         return SYS_ARCH_TIMEOUT;