diff options
| -rw-r--r-- | drivers/tty/tty_ldisc.c | 85 |
1 files changed, 69 insertions, 16 deletions
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index b0500a0a87b8..e4603b09863a 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -492,6 +492,41 @@ static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) } /** + * tty_ldisc_restore - helper for tty ldisc change + * @tty: tty to recover + * @old: previous ldisc + * + * Restore the previous line discipline or N_TTY when a line discipline + * change fails due to an open error + */ + +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)); + 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); + } +} + +/** * tty_set_ldisc - set line discipline * @tty: the terminal to set * @ldisc: the line discipline @@ -504,7 +539,12 @@ static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) int tty_set_ldisc(struct tty_struct *tty, int disc) { - int retval, old_disc; + int retval; + struct tty_ldisc *old_ldisc, *new_ldisc; + + new_ldisc = tty_ldisc_get(tty, disc); + if (IS_ERR(new_ldisc)) + return PTR_ERR(new_ldisc); tty_lock(tty); retval = tty_ldisc_lock(tty, 5 * HZ); @@ -517,8 +557,7 @@ int tty_set_ldisc(struct tty_struct *tty, int disc) } /* Check the no-op case */ - old_disc = tty->ldisc->ops->num; - if (old_disc == disc) + if (tty->ldisc->ops->num == disc) goto out; if (test_bit(TTY_HUPPED, &tty->flags)) { @@ -527,25 +566,34 @@ int tty_set_ldisc(struct tty_struct *tty, int disc) goto out; } - retval = tty_ldisc_reinit(tty, disc); + old_ldisc = tty->ldisc; + + /* Shutdown the old discipline. */ + tty_ldisc_close(tty, old_ldisc); + + /* Now set up the new line discipline. */ + tty->ldisc = new_ldisc; + tty_set_termios_ldisc(tty, disc); + + retval = tty_ldisc_open(tty, new_ldisc); if (retval < 0) { /* Back to the old one or N_TTY if we can't */ - if (tty_ldisc_reinit(tty, old_disc) < 0) { - pr_err("tty: TIOCSETD failed, reinitializing N_TTY\n"); - if (tty_ldisc_reinit(tty, N_TTY) < 0) { - /* At this point we have tty->ldisc == NULL. */ - pr_err("tty: reinitializing N_TTY failed\n"); - } - } + tty_ldisc_put(new_ldisc); + tty_ldisc_restore(tty, old_ldisc); } - if (tty->ldisc && tty->ldisc->ops->num != old_disc && - tty->ops->set_ldisc) { + if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { down_read(&tty->termios_rwsem); tty->ops->set_ldisc(tty); up_read(&tty->termios_rwsem); } + /* At this point we hold a reference to the new ldisc and a + reference to the old ldisc, or we hold two references to + the old ldisc (if it was restored as part of error cleanup + above). In either case, releasing a single reference from + the old ldisc is correct. */ + new_ldisc = old_ldisc; out: tty_ldisc_unlock(tty); @@ -553,6 +601,7 @@ out: already running */ tty_buffer_restart_work(tty->port); err: + tty_ldisc_put(new_ldisc); /* drop the extra reference */ tty_unlock(tty); return retval; } @@ -613,8 +662,10 @@ int tty_ldisc_reinit(struct tty_struct *tty, int disc) int retval; ld = tty_ldisc_get(tty, disc); - if (IS_ERR(ld)) + if (IS_ERR(ld)) { + BUG_ON(disc == N_TTY); return PTR_ERR(ld); + } if (tty->ldisc) { tty_ldisc_close(tty, tty->ldisc); @@ -626,8 +677,10 @@ int tty_ldisc_reinit(struct tty_struct *tty, int disc) tty_set_termios_ldisc(tty, disc); retval = tty_ldisc_open(tty, tty->ldisc); if (retval) { - tty_ldisc_put(tty->ldisc); - tty->ldisc = NULL; + if (!WARN_ON(disc == N_TTY)) { + tty_ldisc_put(tty->ldisc); + tty->ldisc = NULL; + } } return retval; } |