diff options
Diffstat (limited to 'drivers/tty/tty_ldisc.c')
-rw-r--r-- | drivers/tty/tty_ldisc.c | 44 |
1 files changed, 30 insertions, 14 deletions
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index e4603b09863a..4a04567d9aef 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -492,6 +492,29 @@ static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) } /** + * tty_ldisc_failto - helper for ldisc failback + * @tty: tty to open the ldisc on + * @ld: ldisc we are trying to fail back to + * + * Helper to try and recover a tty when switching back to the old + * ldisc fails and we need something attached. + */ + +static int tty_ldisc_failto(struct tty_struct *tty, int ld) +{ + struct tty_ldisc *disc = tty_ldisc_get(tty, ld); + int r; + + if (IS_ERR(disc)) + return PTR_ERR(disc); + tty->ldisc = disc; + tty_set_termios_ldisc(tty, ld); + if ((r = tty_ldisc_open(tty, disc)) < 0) + tty_ldisc_put(disc); + return r; +} + +/** * tty_ldisc_restore - helper for tty ldisc change * @tty: tty to recover * @old: previous ldisc @@ -502,9 +525,6 @@ static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) { - struct tty_ldisc *new_ldisc; - int r; - /* There is an outstanding reference here so this is safe */ old = tty_ldisc_get(tty, old->ops->num); WARN_ON(IS_ERR(old)); @@ -512,17 +532,13 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) tty_set_termios_ldisc(tty, old->ops->num); if (tty_ldisc_open(tty, old) < 0) { tty_ldisc_put(old); - /* This driver is always present */ - new_ldisc = tty_ldisc_get(tty, N_TTY); - if (IS_ERR(new_ldisc)) - panic("n_tty: get"); - tty->ldisc = new_ldisc; - tty_set_termios_ldisc(tty, N_TTY); - r = tty_ldisc_open(tty, new_ldisc); - if (r < 0) - panic("Couldn't open N_TTY ldisc for " - "%s --- error %d.", - tty_name(tty), r); + /* The traditional behaviour is to fall back to N_TTY, we + want to avoid falling back to N_NULL unless we have no + choice to avoid the risk of breaking anything */ + if (tty_ldisc_failto(tty, N_TTY) < 0 && + tty_ldisc_failto(tty, N_NULL) < 0) + panic("Couldn't open N_NULL ldisc for %s.", + tty_name(tty)); } } |