From 21622939fc452c7fb739464b8e49368c3ceaa0ee Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Mon, 11 Mar 2013 16:44:21 -0400 Subject: [PATCH] tty: Add diagnostic for halted line discipline 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 Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_tty.c | 8 ++++++++ drivers/tty/tty_ldisc.c | 7 ++++++- include/linux/tty.h | 1 + 3 files changed, 15 insertions(+), 1 deletion(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 68865d9af8a0..16793eccc6ae 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -153,6 +153,12 @@ 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); } } @@ -1624,6 +1630,8 @@ 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 d794087c327e..c641321b9404 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); @@ -513,8 +514,11 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) static int tty_ldisc_halt(struct tty_struct *tty) { + int scheduled; clear_bit(TTY_LDISC, &tty->flags); - return cancel_work_sync(&tty->port->buf.work); + scheduled = cancel_work_sync(&tty->port->buf.work); + set_bit(TTY_LDISC_HALTED, &tty->flags); + return scheduled; } /** @@ -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 d3548f871968..66ae020e8a98 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)) -- 2.20.1