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Commit 9191aaaa authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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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: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3f40f5b2

drivers/tty/tty_ldisc.c

+4 −1
Original line number Diff line number Diff line
@@ -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