[PATCH 1/4] n_tty: Encapsulate minimum_to_wake within N_TTY

Peter Hurley
2013-06-15T11:29:07Z

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>
---
drivers/tty/n_tty.c | 39 +++++++++++++++++++++++++++------------
drivers/tty/tty_io.c | 17 +++++++++--------
include/linux/tty.h | 1 -
include/linux/tty_ldisc.h | 6 ++++++
4 files changed, 42 insertions(+), 21 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index cdcdb0e..f1806de 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -89,6 +89,7 @@ struct n_tty_data {
int read_head;
int read_tail;
int read_cnt;
+ int minimum_to_wake;

unsigned char *echo_buf;
unsigned int echo_pos;
@@ -1455,7 +1456,7 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,

n_tty_set_room(tty);

- if ((!ldata->icanon && (ldata->read_cnt >= tty->minimum_to_wake)) ||
+ if ((!ldata->icanon && (ldata->read_cnt >= ldata->minimum_to_wake)) ||
L_EXTPROC(tty)) {
kill_fasync(&tty->fasync, SIGIO, POLL_IN);
if (waitqueue_active(&tty->read_wait))
@@ -1636,7 +1637,7 @@ static int n_tty_open(struct tty_struct *tty)
tty->disc_data = ldata;
reset_buffer_flags(tty->disc_data);
ldata->column = 0;
- tty->minimum_to_wake = 1;
+ ldata->minimum_to_wake = 1;
tty->closing = 0;
/* indicate buffer work may resume */
clear_bit(TTY_LDISC_HALTED, &tty->flags);
@@ -1804,17 +1805,17 @@ do_it_again:
minimum = MIN_CHAR(tty);
if (minimum) {
if (time)
- tty->minimum_to_wake = 1;
+ ldata->minimum_to_wake = 1;
else if (!waitqueue_active(&tty->read_wait) ||
- (tty->minimum_to_wake > minimum))
- tty->minimum_to_wake = minimum;
+ (ldata->minimum_to_wake > minimum))
+ ldata->minimum_to_wake = minimum;
} else {
timeout = 0;
if (time) {
timeout = time;
time = 0;
}
- tty->minimum_to_wake = minimum = 1;
+ ldata->minimum_to_wake = minimum = 1;
}
}

@@ -1854,9 +1855,9 @@ do_it_again:
TASK_RUNNING. */
set_current_state(TASK_INTERRUPTIBLE);

- if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
+ if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
((minimum - (b - buf)) >= 1))
- tty->minimum_to_wake = (minimum - (b - buf));
+ ldata->minimum_to_wake = (minimum - (b - buf));

if (!input_available_p(tty, 0)) {
if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
@@ -1973,7 +1974,7 @@ do_it_again:
remove_wait_queue(&tty->read_wait, &wait);

if (!waitqueue_active(&tty->read_wait))
- tty->minimum_to_wake = minimum;
+ ldata->minimum_to_wake = minimum;

__set_current_state(TASK_RUNNING);
size = b - buf;
@@ -2105,6 +2106,7 @@ break_out:
static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
poll_table *wait)
{
+ struct n_tty_data *ldata = tty->disc_data;
unsigned int mask = 0;

poll_wait(file, &tty->read_wait, wait);
@@ -2119,9 +2121,9 @@ static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
mask |= POLLHUP;
if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
if (MIN_CHAR(tty) && !TIME_CHAR(tty))
- tty->minimum_to_wake = MIN_CHAR(tty);
+ ldata->minimum_to_wake = MIN_CHAR(tty);
else
- tty->minimum_to_wake = 1;
+ ldata->minimum_to_wake = 1;
}
if (tty->ops->write && !tty_is_writelocked(tty) &&
tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
@@ -2169,6 +2171,18 @@ static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
}
}

+static void n_tty_fasync(struct tty_struct *tty, int on)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ if (!waitqueue_active(&tty->read_wait)) {
+ if (on)
+ ldata->minimum_to_wake = 1;
+ else if (!tty->fasync)
+ ldata->minimum_to_wake = N_TTY_BUF_SIZE;
+ }
+}
+
struct tty_ldisc_ops tty_ldisc_N_TTY = {
.magic = TTY_LDISC_MAGIC,
.name = "n_tty",
@@ -2182,7 +2196,8 @@ struct tty_ldisc_ops tty_ldisc_N_TTY = {
.set_termios = n_tty_set_termios,
.poll = n_tty_poll,
.receive_buf = n_tty_receive_buf,
- .write_wakeup = n_tty_write_wakeup
+ .write_wakeup = n_tty_write_wakeup,
+ .fasync = n_tty_fasync,
};

/**
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 5ee51ba..6cd08d9 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2137,6 +2137,7 @@ 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;

@@ -2147,11 +2148,17 @@ 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;
@@ -2164,13 +2171,7 @@ 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;
}
diff --git a/include/linux/tty.h b/include/linux/tty.h
index a665c7e..7269daf 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -272,7 +272,6 @@ struct tty_struct {
#define N_TTY_BUF_SIZE 4096

unsigned char closing:1;
- unsigned short minimum_to_wake;
unsigned char *write_buf;
int write_cnt;
/* If the tty has a pending do_SAK, queue it here - akpm */
diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h
index 22ee107..23bdd9d 100644
--- a/include/linux/tty_ldisc.h
+++ b/include/linux/tty_ldisc.h
@@ -100,6 +100,11 @@
* seek to perform this action quickly but should wait until
* any pending driver I/O is completed.
*
+ * void (*fasync)(struct tty_struct *, int on)
+ *
+ * Notify line discipline when signal-driven I/O is enabled or
+ * disabled.
+ *
* void (*dcd_change)(struct tty_struct *tty, unsigned int status)
*
* Tells the discipline that the DCD pin has changed its status.
@@ -189,6 +194,7 @@ struct tty_ldisc_ops {
char *fp, int count);
void (*write_wakeup)(struct tty_struct *);
void (*dcd_change)(struct tty_struct *, unsigned int);
+ void (*fasync)(struct tty_struct *tty, int on);

struct module *owner;

--
1.8.1.2