Hugh Dickins <[EMAIL PROTECTED]> writes:
> I get a hang at startup or shutdown: tiocsctty() holds tty_mutex, and
> now with Eric's tty-in-tiocsctty-when-we-steal-a-tty-hang-it-up.patch
> it can end up calling con_close(), which tries to take tty_mutex.
> So best revert that in hot-fixes, until Eric provides a better.
Well I'm confused I know I tested this, and I even added a printk and
saw it trigger a couple of times.
Hmm. Looking at the code it is clearly not safe to hold the tty_mutex
when calling tty_vhangup. I thought the other caller in tty_io.c was doing
that but on a second glance it is clearly not. And the hangup and close
methods do seem to take the tty_mutex.
How this worked in my testing is beyond me..
I will see if I can generate a better patch later.
Acked-by: Eric W. Biederman <[EMAIL PROTECTED]>
>
> Signed-off-by: Hugh Dickins <[EMAIL PROTECTED]>
>
> --- 2.6.21-rc4-mm1/drivers/char/tty_io.c 2007-03-20 12:49:34.000000000 +0000
> +++ linux/drivers/char/tty_io.c 2007-03-20 18:14:53.000000000 +0000
> @@ -2980,7 +2980,9 @@ static int tiocsctty(struct tty_struct *
> /*
> * Steal it away
> */
> - tty_vhangup(tty);
> + read_lock(&tasklist_lock);
> + session_clear_tty(tty->session);
> + read_unlock(&tasklist_lock);
> } else {
> ret = -EPERM;
> goto unlock;
-
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