Messages in this thread | | | Subject | Re: [PATCHv3 4/6] tty/lockdep: Add ldisc_sem asserts | From | Dmitry Safonov <> | Date | Tue, 11 Sep 2018 13:53:44 +0100 |
| |
On Tue, 2018-09-11 at 14:01 +0200, Peter Zijlstra wrote: > On Tue, Sep 11, 2018 at 02:48:19AM +0100, Dmitry Safonov wrote: > > Make sure under CONFIG_LOCKDEP that each change to line discipline > > is done with held write semaphor. > > But you don't do that. You just assert it is held, not for writing. > > > Otherwise potential reader will have a good time dereferencing > > incomplete/uninitialized ldisc. > > > > Exception here is tty_ldisc_open(), as it's called without > > ldisc_sem > > locked by tty_init_dev() for the tty->link. > > You fail to explain how that is not broken...
I'll add the explanation to the next version.
> > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > Cc: Jiri Slaby <jslaby@suse.com> > > Signed-off-by: Dmitry Safonov <dima@arista.com> > > --- > > drivers/tty/tty_ldisc.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c > > index fc4c97cae01e..202cb645582f 100644 > > --- a/drivers/tty/tty_ldisc.c > > +++ b/drivers/tty/tty_ldisc.c > > @@ -471,6 +471,7 @@ static int tty_ldisc_open(struct tty_struct > > *tty, struct tty_ldisc *ld) > > > > static void tty_ldisc_close(struct tty_struct *tty, struct > > tty_ldisc *ld) > > { > > + lockdep_assert_held(&tty->ldisc_sem); > > Did you want: > > lockdep_assert_held_exclusive(&tty->ldisc_sem); > > ?
Oh, yes, thanks.
> > > WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); > > clear_bit(TTY_LDISC_OPEN, &tty->flags); > > if (ld->ops->close)
-- Thanks, Dmitry
| |