From bee6741ca022f051ea1b46e16fb2ff0097643181 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 9 Jan 2016 21:45:09 -0800 Subject: tty, n_tty: Remove fasync() ldisc notification Only the N_TTY line discipline implements the signal-driven i/o notification enabled/disabled by fcntl(F_SETFL, O_ASYNC). The ldisc fasync() notification is sent to the ldisc when the enable state has changed (the tty core is notified via the fasync() VFS file operation). The N_TTY line discipline used the enable state to change the wakeup condition (minimum_to_wake = 1) for notifying the signal handler i/o is available. However, just the presence of data is sufficient and necessary to signal i/o is available, so changing minimum_to_wake is unnecessary (and creates a race condition with read() and poll() which may be concurrently updating minimum_to_wake). Furthermore, since the kill_fasync() VFS helper performs no action if the fasync list is empty, calling unconditionally is preferred; if signal driven i/o just has been disabled, no signal will be sent by kill_fasync() anyway so notification of the change via the ldisc fasync() method is superfluous. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_tty.c | 5 ----- 1 file changed, 5 deletions(-) (limited to 'drivers/tty/n_tty.c') diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index d04f398d5de3..a93e4c7e82ae 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -2448,10 +2448,6 @@ static int n_tty_ioctl(struct tty_struct *tty, struct file *file, } } -static void n_tty_fasync(struct tty_struct *tty, int on) -{ -} - static struct tty_ldisc_ops n_tty_ops = { .magic = TTY_LDISC_MAGIC, .name = "n_tty", @@ -2465,7 +2461,6 @@ static struct tty_ldisc_ops n_tty_ops = { .poll = n_tty_poll, .receive_buf = n_tty_receive_buf, .write_wakeup = n_tty_write_wakeup, - .fasync = n_tty_fasync, .receive_buf2 = n_tty_receive_buf2, }; -- cgit v1.2.3-59-g8ed1b