From: Alan Cox <[email protected]>
We need to do this in one pass with the locking requirements we now
have.
Signed-off-by: Alan Cox <[email protected]>
---
drivers/tty/tty_ldisc.c | 40 +++++++++++++++++++++++-----------------
1 files changed, 23 insertions(+), 17 deletions(-)
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 833e851..ecfaef5 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -894,6 +894,23 @@ int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
tty_ldisc_enable(tty);
return 0;
}
+
+static int tty_ldisc_kill(struct tty_struct *tty)
+{
+ mutex_lock(&tty->ldisc_mutex);
+ /*
+ * Now kill off the ldisc
+ */
+ tty_ldisc_close(tty, tty->ldisc);
+ tty_ldisc_put(tty->ldisc);
+ /* Force an oops if we mess this up */
+ tty->ldisc = NULL;
+
+ /* Ensure the next open requests the N_TTY ldisc */
+ tty_set_termios_ldisc(tty, N_TTY);
+ mutex_unlock(&tty->ldisc_mutex);
+}
+
/**
* tty_ldisc_release - release line discipline
* @tty: tty being shut down
@@ -912,30 +929,19 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
* race with the set_ldisc code path.
*/
- /* We don't give a monkeys' about the o_tty lock here but we
- must do both to avoid lock inversions against another single
- locking case */
tty_unlock_pair(tty, o_tty);
tty_ldisc_halt(tty);
tty_ldisc_flush_works(tty);
+ if (o_tty) {
+ tty_ldisc_halt(o_tty);
+ tty_ldisc_flush_works(o_tty);
+ }
tty_lock_pair(tty, o_tty);
- mutex_lock(&tty->ldisc_mutex);
- /*
- * Now kill off the ldisc
- */
- tty_ldisc_close(tty, tty->ldisc);
- tty_ldisc_put(tty->ldisc);
- /* Force an oops if we mess this up */
- tty->ldisc = NULL;
-
- /* Ensure the next open requests the N_TTY ldisc */
- tty_set_termios_ldisc(tty, N_TTY);
- mutex_unlock(&tty->ldisc_mutex);
- /* This will need doing differently if we need to lock */
+ tty_ldisc_kill(tty);
if (o_tty)
- tty_ldisc_release(o_tty, NULL);
+ tty_ldisc_kill(o_tty);
/* And the memory resources remaining (buffers, termios) will be
disposed of when the kref hits zero */
On Fri, May 25, 2012 at 1:11 PM, Alan Cox <[email protected]> wrote:
> From: Alan Cox <[email protected]>
>
> We need to do this in one pass with the locking requirements we now
> have.
>
> Signed-off-by: Alan Cox <[email protected]>
> ---
I don't see any lockdep warnings anymore with this patch applied on
top of all others.
On Fri, 25 May 2012 13:13:15 +0200
Sasha Levin <[email protected]> wrote:
> On Fri, May 25, 2012 at 1:11 PM, Alan Cox <[email protected]> wrote:
> > From: Alan Cox <[email protected]>
> >
> > We need to do this in one pass with the locking requirements we now
> > have.
> >
> > Signed-off-by: Alan Cox <[email protected]>
> > ---
>
> I don't see any lockdep warnings anymore with this patch applied on
> top of all others.
Yay thanks for reporting/testing
On Fri, May 25, 2012 at 7:11 PM, Alan Cox <[email protected]> wrote:
> From: Alan Cox <[email protected]>
>
> We need to do this in one pass with the locking requirements we now
> have.
>
> Signed-off-by: Alan Cox <[email protected]>
> ---
>
> ?drivers/tty/tty_ldisc.c | ? 40 +++++++++++++++++++++++-----------------
> ?1 files changed, 23 insertions(+), 17 deletions(-)
>
>
> diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
> index 833e851..ecfaef5 100644
> --- a/drivers/tty/tty_ldisc.c
> +++ b/drivers/tty/tty_ldisc.c
> @@ -894,6 +894,23 @@ int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
> ? ? ? ?tty_ldisc_enable(tty);
> ? ? ? ?return 0;
> ?}
> +
> +static int tty_ldisc_kill(struct tty_struct *tty)
Maybe the return type should be defined as void to avoid compile warning.
After applying Alan's three patches for addressing tty locks and the patch
int the below link:
http://marc.info/?l=linux-kernel&m=133775308420817&w=2
Looks no lockdep warnings are triggered any more when running
'exit' in shell of ssh session.
So I will send out the formal patch in the above link.
Thanks,
--
Ming Lei