[GitHub] [incubator-nuttx] gustavonihei commented on a change in pull request #5017: libc: Enable terminal api regardless of CONFIG_SERIAL_TERMIOS setting

[GitBox <gi...@apache.org>]

gustavonihei commented on a change in pull request #5017:
URL: https://github.com/apache/incubator-nuttx/pull/5017#discussion_r773343212



##########
File path: drivers/serial/serial.c
##########
@@ -1332,12 +1333,28 @@ static int uart_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
             }
             break;
 
-#ifdef CONFIG_SERIAL_TERMIOS
           case TCFLSH:
             {
               /* Empty the tx/rx buffers */
 
-              irqstate_t flags = enter_critical_section();
+              irqstate_t flags;
+
+              /* tcdrain is a cancellation point */
+
+              if (enter_cancellation_point())

Review comment:
       According to the latest version of the Open Group standard, `tcdrain` is required to be a thread cancellation point:
   https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_09_05_02
   
   So, strictly speaking, the most correct would be to set the cancellation point inside `tcdrain()`.
   Even so, it wouldn't compromise the points raised by @xiaoxiang781216, since it would still continue to be a userspace wrapper around the `TCDRN` ioctl call.




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