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authorPeter Hurley <peter@hurleysoftware.com>2016-01-10 08:45:09 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-01-28 22:58:02 +0300
commitbee6741ca022f051ea1b46e16fb2ff0097643181 (patch)
tree9d35e064e4a4013328ee3c74f9dc8833534918c5 /drivers/tty/tty_io.c
parent33d7136336a94feade73b08b9c4bd1420df4e572 (diff)
downloadlinux-bee6741ca022f051ea1b46e16fb2ff0097643181.tar.xz
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 <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/tty_io.c')
-rw-r--r--drivers/tty/tty_io.c8
1 files changed, 0 insertions, 8 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index c5b4274584dc..7533ab1abe72 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2219,7 +2219,6 @@ static unsigned int tty_poll(struct file *filp, poll_table *wait)
static int __tty_fasync(int fd, struct file *filp, int on)
{
struct tty_struct *tty = file_tty(filp);
- struct tty_ldisc *ldisc;
unsigned long flags;
int retval = 0;
@@ -2230,13 +2229,6 @@ static int __tty_fasync(int fd, struct file *filp, int on)
if (retval <= 0)
goto out;
- ldisc = tty_ldisc_ref(tty);
- if (ldisc) {
- if (ldisc->ops->fasync)
- ldisc->ops->fasync(tty, on);
- tty_ldisc_deref(ldisc);
- }
-
if (on) {
enum pid_type type;
struct pid *pid;