Flip buffer work must not be scheduled by the line discipline after the line discipline has been halted; issue warning.
Note: drivers can still schedule flip buffer work. Signed-off-by: Peter Hurley <[email protected]> --- drivers/tty/n_tty.c | 8 ++++++++ drivers/tty/tty_ldisc.c | 45 +++++++++++++++++++++++++-------------------- include/linux/tty.h | 1 + 3 files changed, 34 insertions(+), 20 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 19083ef..bf6958b 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -152,6 +152,12 @@ static void n_tty_set_room(struct tty_struct *tty) if (left && !old_left) { WARN_RATELIMIT(tty->port->itty == NULL, "scheduling with invalid itty\n"); + /* see if ldisc has been killed - if so, this means that + * even though the ldisc has been halted and ->buf.work + * cancelled, ->buf.work is about to be rescheduled + */ + WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags), + "scheduling buffer work for halted ldisc\n"); schedule_work(&tty->port->buf.work); } } @@ -1644,6 +1650,8 @@ static int n_tty_open(struct tty_struct *tty) goto err_free_bufs; tty->disc_data = ldata; + /* indicate buffer work may resume */ + clear_bit(TTY_LDISC_HALTED, &tty->flags); reset_buffer_flags(tty); tty_unthrottle(tty); ldata->column = 0; diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index d794087..904bf75 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -375,6 +375,7 @@ static inline void tty_ldisc_put(struct tty_ldisc *ld) void tty_ldisc_enable(struct tty_struct *tty) { + clear_bit(TTY_LDISC_HALTED, &tty->flags); set_bit(TTY_LDISC, &tty->flags); clear_bit(TTY_LDISC_CHANGING, &tty->flags); wake_up(&tty_ldisc_wait); @@ -498,26 +499,6 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) } /** - * tty_ldisc_halt - shut down the line discipline - * @tty: tty device - * - * Shut down the line discipline and work queue for this tty device. - * The TTY_LDISC flag being cleared ensures no further references can - * be obtained while the delayed work queue halt ensures that no more - * data is fed to the ldisc. - * - * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex) - * in order to make sure any currently executing ldisc work is also - * flushed. - */ - -static int tty_ldisc_halt(struct tty_struct *tty) -{ - clear_bit(TTY_LDISC, &tty->flags); - return cancel_work_sync(&tty->port->buf.work); -} - -/** * tty_ldisc_flush_works - flush all works of a tty * @tty: tty device to flush works for * @@ -547,6 +528,29 @@ static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout) } /** + * tty_ldisc_halt - shut down the line discipline + * @tty: tty device + * + * Shut down the line discipline and work queue for this tty device. + * The TTY_LDISC flag being cleared ensures no further references can + * be obtained while the delayed work queue halt ensures that no more + * data is fed to the ldisc. + * + * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex) + * in order to make sure any currently executing ldisc work is also + * flushed. + */ + +static int tty_ldisc_halt(struct tty_struct *tty) +{ + int scheduled; + clear_bit(TTY_LDISC, &tty->flags); + scheduled = cancel_work_sync(&tty->port->buf.work); + set_bit(TTY_LDISC_HALTED, &tty->flags); + return scheduled; +} + +/** * tty_set_ldisc - set line discipline * @tty: the terminal to set * @ldisc: the line discipline @@ -820,6 +824,7 @@ void tty_ldisc_hangup(struct tty_struct *tty) clear_bit(TTY_LDISC, &tty->flags); tty_unlock(tty); cancel_work_sync(&tty->port->buf.work); + set_bit(TTY_LDISC_HALTED, &tty->flags); mutex_unlock(&tty->ldisc_mutex); retry: tty_lock(tty); diff --git a/include/linux/tty.h b/include/linux/tty.h index c75d886..7aa4be6 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -315,6 +315,7 @@ struct tty_file_private { #define TTY_NO_WRITE_SPLIT 17 /* Preserve write boundaries to driver */ #define TTY_HUPPED 18 /* Post driver->hangup() */ #define TTY_HUPPING 21 /* ->hangup() in progress */ +#define TTY_LDISC_HALTED 22 /* Line discipline is halted */ #define TTY_WRITE_FLUSH(tty) tty_write_flush((tty)) -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
