> In tty layer, it use tty->ldisc_sem to proect tty_ldisc_ops. > So I think tty->ldisc_sem can also protect tty->disc_data; It might help by CC'ing TTY people, so that we could get this reviewed by people who are familiar with TTY code. Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> (supporter:TTY LAYER) Jiri Slaby <jirislaby@xxxxxxxxxx> (supporter:TTY LAYER) Thanks! > For examlpe, > When cpu A is running ppp_synctty_ioctl that hold the tty->ldisc_sem, > at the same time if cpu B calls ppp_synctty_close, it will wait until > cpu A release tty->ldisc_sem. So I think it is unnecessary to have the > disc_data_lock; > > cpu A cpu B > tty_ioctl tty_reopen > ->hold tty->ldisc_sem ->hold tty->ldisc_sem(write), failed > ->ld->ops->ioctl ->wait... > ->release tty->ldisc_sem ->wait...OK,hold tty->ldisc_sem > ->tty_ldisc_reinit > ->tty_ldisc_close > ->ld->ops->close IMHO an example might not be necessary. Examples are useful to show incorrectness. But we cannot show correctness by examples because examples are not exhaustive. BTW, there're some typos: "proect" -> "protect" "examlpe" -> "example" "that hold ..." -> "that holds ..." "cpu A release ..." -> "cpu A releases ..." > * FIXME: this is no longer true. The _close path for the ldisc is > * now guaranteed to be sane. > */ > * > * FIXME: Fixed in tty_io nowadays. > */ Since you are removing "disc_data_lock", please update (or remove) these two comments. Thanks!
