[PATCH 3/4] tty: Abstract and encapsulate tty->closing behavior

From: Peter Hurley
Date: Sun Nov 08 2015 - 17:03:26 EST

tty->closing is exclusively used to cause the N_TTY line discipline
to drop further input on final tty close (except XON/XOFF output flow
control changes). In turn, this prevents the line discipline from
generating new tty driver i/o requests (eg., when echoing) after the tty
driver has performed h/w shutdown.

Abstract this notification with new ldisc api function,
tty_ldisc_closing(), which invokes the new line discipline method,
ops->closing(). Define this method for N_TTY line discipline and
localize closing state to n_tty private data. Remove tty->closing.

Note that resetting tty->closing to 0 (and thus allowing the
line discipline to resume normal input processing) is unnecessary
and undesirable: since the tty is in final close, both the line
discipline instance and the tty are being destroyed, so resuming normal
input processing after h/w shutdown is counter-productive.

NB: ipwireless_tty_free() is completely bogus; freeing the tty (?!) with
open, in-use file descriptors is laughable.

Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
---
drivers/isdn/i4l/isdn_tty.c | 2 +-
drivers/s390/char/con3215.c | 3 +--
drivers/staging/dgap/dgap.c | 4 +---
drivers/staging/dgnc/dgnc_tty.c | 4 +---
drivers/tty/hvc/hvsi.c | 2 +-
drivers/tty/ipwireless/tty.c | 1 -
drivers/tty/n_tty.c | 13 +++++++++++--
drivers/tty/rocket.c | 1 -
drivers/tty/serial/68328serial.c | 3 +--
drivers/tty/serial/crisv10.c | 3 +--
drivers/tty/serial/serial_core.c | 1 -
drivers/tty/tty_ldisc.c | 19 +++++++++++++++++++
drivers/tty/tty_port.c | 3 +--
include/linux/tty.h | 2 +-
include/linux/tty_ldisc.h | 9 +++++++++
15 files changed, 48 insertions(+), 22 deletions(-)

diff --git a/drivers/isdn/i4l/isdn_tty.c b/drivers/isdn/i4l/isdn_tty.c
index 2175225..cddba25 100644
--- a/drivers/isdn/i4l/isdn_tty.c
+++ b/drivers/isdn/i4l/isdn_tty.c
@@ -1574,7 +1574,7 @@ isdn_tty_close(struct tty_struct *tty, struct file *filp)
}
port->flags |= ASYNC_CLOSING;

- tty->closing = 1;
+ tty_ldisc_closing(tty);
/*
* At this point we stop accepting input. To do this, we
* disable the receive line status interrupts, and tell the
diff --git a/drivers/s390/char/con3215.c b/drivers/s390/char/con3215.c
index 0fc3fe5..715251d 100644
--- a/drivers/s390/char/con3215.c
+++ b/drivers/s390/char/con3215.c
@@ -1006,11 +1006,10 @@ static void tty3215_close(struct tty_struct *tty, struct file * filp)
raw = (struct raw3215_info *) tty->driver_data;
if (raw == NULL || tty->count > 1)
return;
- tty->closing = 1;
+ tty_ldisc_closing(tty);
/* Shutdown the terminal */
raw3215_shutdown(raw);
tasklet_kill(&raw->tlet);
- tty->closing = 0;
tty_port_tty_set(&raw->port, NULL);
}

diff --git a/drivers/staging/dgap/dgap.c b/drivers/staging/dgap/dgap.c
index 9112dd2..0456e28 100644
--- a/drivers/staging/dgap/dgap.c
+++ b/drivers/staging/dgap/dgap.c
@@ -4622,7 +4622,7 @@ static void dgap_tty_close(struct tty_struct *tty, struct file *file)

un->un_flags |= UN_CLOSING;

- tty->closing = 1;
+ tty_ldisc_closing(tty);

/*
* Only officially close channel if count is 0 and
@@ -4645,8 +4645,6 @@ static void dgap_tty_close(struct tty_struct *tty, struct file *file)

spin_lock_irqsave(&ch->ch_lock, lock_flags);

- tty->closing = 0;
-
/*
* If we have HUPCL set, lower DTR and RTS
*/
diff --git a/drivers/staging/dgnc/dgnc_tty.c b/drivers/staging/dgnc/dgnc_tty.c
index fbfe79a..96960d8 100644
--- a/drivers/staging/dgnc/dgnc_tty.c
+++ b/drivers/staging/dgnc/dgnc_tty.c
@@ -1410,7 +1410,7 @@ static void dgnc_tty_close(struct tty_struct *tty, struct file *file)
/* OK, its the last close on the unit */
un->un_flags |= UN_CLOSING;

- tty->closing = 1;
+ tty_ldisc_closing(tty);


/*
@@ -1441,8 +1441,6 @@ static void dgnc_tty_close(struct tty_struct *tty, struct file *file)

spin_lock_irqsave(&ch->ch_lock, flags);

- tty->closing = 0;
-
/*
* If we have HUPCL set, lower DTR and RTS
*/
diff --git a/drivers/tty/hvc/hvsi.c b/drivers/tty/hvc/hvsi.c
index a75146f..fbaa6ab 100644
--- a/drivers/tty/hvc/hvsi.c
+++ b/drivers/tty/hvc/hvsi.c
@@ -796,7 +796,7 @@ static void hvsi_close(struct tty_struct *tty, struct file *filp)
* any data delivered to the tty layer after this will be
* discarded (except for XON/XOFF)
*/
- tty->closing = 1;
+ tty_ldisc_closing(tty);

spin_unlock_irqrestore(&hp->lock, flags);

diff --git a/drivers/tty/ipwireless/tty.c b/drivers/tty/ipwireless/tty.c
index 345cebb..2ed8831 100644
--- a/drivers/tty/ipwireless/tty.c
+++ b/drivers/tty/ipwireless/tty.c
@@ -536,7 +536,6 @@ void ipwireless_tty_free(struct ipw_tty *tty)
printk(KERN_INFO IPWIRELESS_PCCARD_NAME
": deregistering %s device ttyIPWp%d\n",
tty_type_name(ttyj->tty_type), j);
- ttyj->closing = 1;
if (ttyj->port.tty != NULL) {
mutex_unlock(&ttyj->ipw_tty_mutex);
tty_vhangup(ttyj->port.tty);
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 2de0283..6342b37 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -114,6 +114,7 @@ struct n_tty_data {
unsigned char echo_buf[N_TTY_BUF_SIZE];

int minimum_to_wake;
+ int closing;

/* consumer-published */
size_t read_tail;
@@ -1637,7 +1638,7 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
n_tty_receive_buf_real_raw(tty, cp, fp, count);
else if (ldata->raw || (L_EXTPROC(tty) && !preops))
n_tty_receive_buf_raw(tty, cp, fp, count);
- else if (tty->closing && !L_EXTPROC(tty))
+ else if (ldata->closing && !L_EXTPROC(tty))
n_tty_receive_buf_closing(tty, cp, fp, count);
else {
if (ldata->lnext) {
@@ -1942,7 +1943,7 @@ static int n_tty_open(struct tty_struct *tty)
ldata->num_overrun = 0;
ldata->no_room = 0;
ldata->lnext = 0;
- tty->closing = 0;
+ ldata->closing = 0;
/* indicate buffer work may resume */
clear_bit(TTY_LDISC_HALTED, &tty->flags);
n_tty_set_termios(tty, NULL);
@@ -2525,6 +2526,13 @@ static void n_tty_fasync(struct tty_struct *tty, int on)
}
}

+static void n_tty_closing(struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ ldata->closing = 1;
+}
+
struct tty_ldisc_ops tty_ldisc_N_TTY = {
.magic = TTY_LDISC_MAGIC,
.name = "n_tty",
@@ -2541,6 +2549,7 @@ struct tty_ldisc_ops tty_ldisc_N_TTY = {
.write_wakeup = n_tty_write_wakeup,
.fasync = n_tty_fasync,
.receive_buf2 = n_tty_receive_buf2,
+ .closing = n_tty_closing,
};

/**
diff --git a/drivers/tty/rocket.c b/drivers/tty/rocket.c
index c5179f8..a6b5ce0 100644
--- a/drivers/tty/rocket.c
+++ b/drivers/tty/rocket.c
@@ -1043,7 +1043,6 @@ static void rp_close(struct tty_struct *tty, struct file *filp)
}
spin_lock_irq(&port->lock);
info->port.flags &= ~(ASYNC_INITIALIZED | ASYNC_CLOSING | ASYNC_NORMAL_ACTIVE);
- tty->closing = 0;
spin_unlock_irq(&port->lock);
mutex_unlock(&port->mutex);
tty_port_tty_set(port, NULL);
diff --git a/drivers/tty/serial/68328serial.c b/drivers/tty/serial/68328serial.c
index 0140ba4..9a6aaf0 100644
--- a/drivers/tty/serial/68328serial.c
+++ b/drivers/tty/serial/68328serial.c
@@ -1035,7 +1035,7 @@ static void rs_close(struct tty_struct *tty, struct file * filp)
* Now we wait for the transmit buffer to clear; and we notify
* the line discipline to only process XON/XOFF characters.
*/
- tty->closing = 1;
+ tty_ldisc_closing(tty);
if (port->closing_wait != ASYNC_CLOSING_WAIT_NONE)
tty_wait_until_sent(tty, port->closing_wait);
/*
@@ -1052,7 +1052,6 @@ static void rs_close(struct tty_struct *tty, struct file * filp)
rs_flush_buffer(tty);

tty_ldisc_flush(tty);
- tty->closing = 0;
tty_port_tty_set(&info->tport, NULL);
#warning "This is not and has never been valid so fix it"
#if 0
diff --git a/drivers/tty/serial/crisv10.c b/drivers/tty/serial/crisv10.c
index f13f2eb..0100410 100644
--- a/drivers/tty/serial/crisv10.c
+++ b/drivers/tty/serial/crisv10.c
@@ -3620,7 +3620,7 @@ rs_close(struct tty_struct *tty, struct file * filp)
* Now we wait for the transmit buffer to clear; and we notify
* the line discipline to only process XON/XOFF characters.
*/
- tty->closing = 1;
+ tty_ldisc_closing(tty);
if (info->port.closing_wait != ASYNC_CLOSING_WAIT_NONE)
tty_wait_until_sent(tty, info->port.closing_wait);
/*
@@ -3646,7 +3646,6 @@ rs_close(struct tty_struct *tty, struct file * filp)
shutdown(info);
rs_flush_buffer(tty);
tty_ldisc_flush(tty);
- tty->closing = 0;
info->event = 0;
info->port.tty = NULL;
if (info->port.blocked_open) {
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index def5199..db27a40 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1441,7 +1441,6 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
mutex_unlock(&port->mutex);

tty_ldisc_flush(tty);
- tty->closing = 0;
}

static void uart_wait_until_sent(struct tty_struct *tty, int timeout)
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index b776f2e..ef6af5f 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -407,6 +407,25 @@ void tty_ldisc_flush(struct tty_struct *tty)
EXPORT_SYMBOL_GPL(tty_ldisc_flush);

/**
+ * tty_ldisc_closing - notify line discipline of final close
+ * @tty: tty
+ *
+ * Notify the line discipline the driver has begun final close of the tty.
+ * The N_TTY line discipline uses this notification to ignore new input
+ */
+
+void tty_ldisc_closing(struct tty_struct *tty)
+{
+ struct tty_ldisc *ld = tty_ldisc_ref(tty);
+
+ if (ld->ops->closing)
+ ld->ops->closing(tty);
+ if (ld)
+ tty_ldisc_deref(ld);
+}
+EXPORT_SYMBOL_GPL(tty_ldisc_closing);
+
+/**
* tty_set_termios_ldisc - set ldisc field
* @tty: tty structure
* @num: line discipline number
diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index a76aec2..ecb6435 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -479,7 +479,7 @@ int tty_port_close_start(struct tty_port *port,
set_bit(ASYNCB_CLOSING, &port->flags);
spin_unlock_irqrestore(&port->lock, flags);

- tty->closing = 1;
+ tty_ldisc_closing(tty);

if (test_bit(ASYNCB_INITIALIZED, &port->flags)) {
/* Don't block on a stalled port, just pull the chain */
@@ -504,7 +504,6 @@ void tty_port_close_end(struct tty_port *port, struct tty_struct *tty)
unsigned long flags;

tty_ldisc_flush(tty);
- tty->closing = 0;

spin_lock_irqsave(&port->lock, flags);

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 4b6c62e..70f3a9c1 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -306,7 +306,6 @@ struct tty_struct {

#define N_TTY_BUF_SIZE 4096

- int closing;
unsigned char *write_buf;
int write_cnt;
/* If the tty has a pending do_SAK, queue it here - akpm */
@@ -498,6 +497,7 @@ extern const struct file_operations tty_ldiscs_proc_fops;

extern void tty_wakeup(struct tty_struct *tty);
extern void tty_ldisc_flush(struct tty_struct *tty);
+extern void tty_ldisc_closing(struct tty_struct *tty);

extern long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
extern int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h
index 00c9d68..0f3b19f 100644
--- a/include/linux/tty_ldisc.h
+++ b/include/linux/tty_ldisc.h
@@ -125,6 +125,14 @@
* received with a parity error, etc. <fp> may be NULL to indicate
* all data received is TTY_NORMAL.
* If assigned, prefer this function for automatic flow control.
+ *
+ * void (*closing)(struct tty_struct *);
+ *
+ * This function notifies the line discipline the driver is
+ * starting final close for this tty; tty and ldisc destruction
+ * is imminent. The N_TTY line discipline uses this notification
+ * to ignore new input other than IXON flow control changes.
+ * This notification is not received for ptys or vts.
*/

#include <linux/fs.h>
@@ -212,6 +220,7 @@ struct tty_ldisc_ops {
void (*fasync)(struct tty_struct *tty, int on);
int (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
char *fp, int count);
+ void (*closing)(struct tty_struct *tty);

struct module *owner;

--
2.6.3

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