Resume TTY on SUSP and fix CRNL order in N_TTY line discipline

Refine these behaviors in the N_TTY line discipline:

1) Handle the signal characters consistently when received in a stopped TTY
   so that SUSP (typically ctrl-Z) behaves like INTR and QUIT in resuming a
   stopped TTY.

2) Adjust the order in which the IGNCR/ICRNL/INLCR processing is applied to
   be more logical and consistent with the behavior of other Unix systems.
Signed-off-by: NJoe Peterson <joe@skyrush.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/n_tty.c

@@ -708,7 +708,7 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
 
 	if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
 	    ((I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty)) ||
-	     c == INTR_CHAR(tty) || c == QUIT_CHAR(tty)))
+	     c == INTR_CHAR(tty) || c == QUIT_CHAR(tty) || c == SUSP_CHAR(tty)))
 		start_tty(tty);
 
 	if (tty->closing) {
@@ -746,13 +746,6 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
 		return;
 	}
 
-	if (c == '\r') {
-		if (I_IGNCR(tty))
-			return;
-		if (I_ICRNL(tty))
-			c = '\n';
-	} else if (c == '\n' && I_INLCR(tty))
-		c = '\r';
 	if (I_IXON(tty)) {
 		if (c == START_CHAR(tty)) {
 			start_tty(tty);
@@ -763,6 +756,7 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
 			return;
 		}
 	}
+
 	if (L_ISIG(tty)) {
 		int signal;
 		signal = SIGINT;
@@ -792,6 +786,15 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
 			return;
 		}
 	}
+
+	if (c == '\r') {
+		if (I_IGNCR(tty))
+			return;
+		if (I_ICRNL(tty))
+			c = '\n';
+	} else if (c == '\n' && I_INLCR(tty))
+		c = '\r';
+
 	if (tty->icanon) {
 		if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
 		    (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {