n_tty: Encapsulate minimum_to_wake within N_TTY
minimum_to_wake is unique to N_TTY processing, and belongs in
per-ldisc data.
Add the ldisc method, ldisc_ops::fasync(), to notify line disciplines
when signal-driven I/O is enabled or disabled. When enabled for N_TTY
(by fcntl(F_SETFL, O_ASYNC)), blocking reader/polls will be woken
for any readable input. When disabled, blocking reader/polls are not
woken until the read buffer is full.
Canonical mode (L_ICANON(tty), n_tty_data::icanon) is not affected by
the minimum_to_wake setting.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 6464029..bd88007 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2138,6 +2138,7 @@
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;
@@ -2148,11 +2149,17 @@
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;
- if (!waitqueue_active(&tty->read_wait))
- tty->minimum_to_wake = 1;
+
spin_lock_irqsave(&tty->ctrl_lock, flags);
if (tty->pgrp) {
pid = tty->pgrp;
@@ -2165,13 +2172,7 @@
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
retval = __f_setown(filp, pid, type, 0);
put_pid(pid);
- if (retval)
- goto out;
- } else {
- if (!tty->fasync && !waitqueue_active(&tty->read_wait))
- tty->minimum_to_wake = N_TTY_BUF_SIZE;
}
- retval = 0;
out:
return retval;
}