n_tty: Output bells immediately on a full buffer

This patch causes "bell" (^G) characters (invoked when the input buffer
is full) to be immediately output rather than filling the echo buffer.

This is especially a problem when the tty is stopped and buffers fill, since
the bells do not serve their purpose of immediate notification that the
buffer cannot take further input, and they will flush all at once when the
tty is restarted.

Signed-off-by: Joe Peterson <joe@skyrush.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/n_tty.c

@@ -872,7 +872,7 @@ static void eraser(unsigned char c, struct tty_struct *tty)
 
 	/* FIXME: locking needed ? */
 	if (tty->read_head == tty->canon_head) {
-		/* echo_char_raw('\a', tty); */ /* what do you think? */
+		/* process_output('\a', tty); */ /* what do you think? */
 		return;
 	}
 	if (c == ERASE_CHAR(tty))
@@ -1148,10 +1148,8 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
 		parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
 		if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
 			/* beep if no space */
-			if (L_ECHO(tty)) {
-				echo_char_raw('\a', tty);
-				process_echoes(tty);
-			}
+			if (L_ECHO(tty))
+				process_output('\a', tty);
 			return;
 		}
 		if (L_ECHO(tty)) {
@@ -1255,10 +1253,8 @@ send_signal:
 		}
 		if (c == '\n') {
 			if (tty->read_cnt >= N_TTY_BUF_SIZE) {
-				if (L_ECHO(tty)) {
-					echo_char_raw('\a', tty);
-					process_echoes(tty);
-				}
+				if (L_ECHO(tty))
+					process_output('\a', tty);
 				return;
 			}
 			if (L_ECHO(tty) || L_ECHONL(tty)) {
@@ -1280,10 +1276,8 @@ send_signal:
 			parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
 				 ? 1 : 0;
 			if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
-				if (L_ECHO(tty)) {
-					echo_char_raw('\a', tty);
-					process_echoes(tty);
-				}
+				if (L_ECHO(tty))
+					process_output('\a', tty);
 				return;
 			}
 			/*
@@ -1320,10 +1314,8 @@ handle_newline:
 	parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
 	if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
 		/* beep if no space */
-		if (L_ECHO(tty)) {
-			echo_char_raw('\a', tty);
-			process_echoes(tty);
-		}
+		if (L_ECHO(tty))
+			process_output('\a', tty);
 		return;
 	}
 	if (L_ECHO(tty)) {