n_tty: Fix poll() when TIME_CHAR and MIN_CHAR == 0

Commit eafbe67f84761d787802e5113d895a316b6292fe,
  n_tty: Refactor input_available_p() by call site
broke poll() when TIME_CHAR(tty) and MIN_CHAR(tty) are both 0.

When TIME_CHAR and MIN_CHAR are both 0, input is available if the
read_cnt is 1 (not 0).

Reported-by: Eric Dumazet <edumazet@google.com>
Tested-by: Eric Dumazet <edumazet@google.com>
Reported-by: Stephane Eranian <eranian@google.com>
Tested-by: David Ahern <dsahern@gmail.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index cb8017aa443472f8b67d9ec4eab7403b268d2c0f..2747a3b20a50b31a621c137bcdef3dd826dcdd77 100644 (file)
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1896,7 +1896,7 @@ err:
 static inline int input_available_p(struct tty_struct *tty, int poll)
 {
        struct n_tty_data *ldata = tty->disc_data;
-       int amt = poll && !TIME_CHAR(tty) ? MIN_CHAR(tty) : 1;
+       int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
 
        if (ldata->icanon && !L_EXTPROC(tty)) {
                if (ldata->canon_head != ldata->read_tail)