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n_tty: Encapsulate minimum_to_wake within N_TTY

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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>
This commit is contained in:
Peter Hurley
2013-06-15 07:28:28 -04:00
committed by Greg Kroah-Hartman
parent a630fbfbb1
commit f6c8dbe6e5
4 changed files with 42 additions and 21 deletions
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17
drivers/tty/tty_io.c
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@@ -2138,6 +2138,7 @@ 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;
@@ -2148,11 +2149,17 @@ 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;
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 @@ static int __tty_fasync(int fd, struct file *filp, int on)
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;
}