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 <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 68865d9..16793ec 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -153,6 +153,12 @@
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 @@
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..c641321 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -375,6 +375,7 @@
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 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 @@
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);