From: Peter Hurley Date: Wed, 5 Nov 2014 18:11:41 +0000 (-0500) Subject: tty: Allow safe access to termios for set_ldisc() handlers X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=9191aaaa82d3149767125d58b2d260a3749d9f5e;p=linux-beck.git tty: Allow safe access to termios for set_ldisc() handlers Allow a tty driver to safely access termios settings while handling the set_ldisc() notification. UART drivers use the set_ldisc() notification to check if the N_PPS line discipline is being enabled; if so, modem status interrupts may also need to be enabled. Conversely, modem status interrupts may need to be disabled if switching away from the N_PPS line discipline. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index b66a81d0549e..3737f55272d2 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -572,8 +572,11 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) tty_ldisc_restore(tty, old_ldisc); } - if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) + if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { + down_read(&tty->termios_rwsem); tty->ops->set_ldisc(tty); + up_read(&tty->termios_rwsem); + } /* At this point we hold a reference to the new ldisc and a reference to the old ldisc, or we hold two references to