[PATCH 12/35] tty: cumulate and document tty_struct::flow* members

From: Jiri Slaby
Date: Wed May 05 2021 - 05:20:15 EST

Group the flow flags under a single struct called flow. The new struct
contains 'stopped' and 'tco_stopped' bools which used to be bits in a
bitfield. The struct also contains the lock protecting them to
potentially share the same cache line.

Note that commit c545b66c6922b (tty: Serialize tcflow() with other tty
flow control changes) added a padding to the original bitfield. It was
for the bitfield to occupy a whole 64b word to avoid interferring stores
on Alpha (cannot we evaporate this arch with weird implications to C
code yet?). But it doesn't work as expected as the padding
(tty_struct::unused) is aligned to a 8B boundary too and occupies some
bytes from the next word.

So make it reliable by:
1) setting __aligned of the struct -- that aligns the start, and
2) making 'unsigned long unused[0]' as the last member of the struct --
pads the end.

This is also the perfect time to start the documentation of tty_struct
where all this lives. So we start by documenting what these bools
actually serve for. And why we do all the alignment dances. Only the few
up-to-date information from the Theodore's comment made it into this new
Kerneldoc comment.

Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: Shawn Guo <shawnguo@xxxxxxxxxx>
Cc: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Cc: "Maciej W. Rozycki" <macro@xxxxxxxxxxx>
---
Documentation/networking/caif/caif.rst | 4 +--
drivers/char/pcmcia/synclink_cs.c | 8 +++---
drivers/mmc/core/sdio_uart.c | 2 +-
drivers/net/caif/caif_serial.c | 4 +--
drivers/s390/char/tty3270.c | 2 +-
drivers/staging/fwserial/fwserial.c | 2 +-
drivers/tty/amiserial.c | 8 +++---
drivers/tty/moxa.c | 4 +--
drivers/tty/mxser.c | 12 ++++----
drivers/tty/n_tty.c | 8 +++---
drivers/tty/pty.c | 4 +--
drivers/tty/serial/arc_uart.c | 2 +-
drivers/tty/serial/dz.c | 2 +-
drivers/tty/synclink_gt.c | 6 ++--
drivers/tty/tty_io.c | 24 ++++++++--------
drivers/tty/tty_ioctl.c | 16 +++++------
drivers/tty/tty_port.c | 2 +-
drivers/tty/vt/keyboard.c | 2 +-
drivers/tty/vt/vt.c | 4 +--
include/linux/serial_core.h | 2 +-
include/linux/tty.h | 38 +++++++++++++++-----------
include/linux/tty_driver.h | 4 +--
22 files changed, 83 insertions(+), 77 deletions(-)

diff --git a/Documentation/networking/caif/caif.rst b/Documentation/networking/caif/caif.rst
index 81a14373d780..d922d419c513 100644
--- a/Documentation/networking/caif/caif.rst
+++ b/Documentation/networking/caif/caif.rst
@@ -69,9 +69,9 @@ There are debugfs parameters provided for serial communication.

- 0x01 - tty->warned is on.
- 0x04 - tty->packed is on.
- - 0x08 - tty->flow_stopped is on.
+ - 0x08 - tty->flow.tco_stopped is on.
- 0x10 - tty->hw_stopped is on.
- - 0x20 - tty->stopped is on.
+ - 0x20 - tty->flow.stopped is on.

* last_tx_msg: Binary blob Prints the last transmitted frame.

diff --git a/drivers/char/pcmcia/synclink_cs.c b/drivers/char/pcmcia/synclink_cs.c
index 3287a7627ed0..b4707bc3aee8 100644
--- a/drivers/char/pcmcia/synclink_cs.c
+++ b/drivers/char/pcmcia/synclink_cs.c
@@ -985,7 +985,7 @@ static void tx_done(MGSLPC_INFO *info, struct tty_struct *tty)
else
#endif
{
- if (tty && (tty->stopped || tty->hw_stopped)) {
+ if (tty && (tty->flow.stopped || tty->hw_stopped)) {
tx_stop(info);
return;
}
@@ -1005,7 +1005,7 @@ static void tx_ready(MGSLPC_INFO *info, struct tty_struct *tty)
if (!info->tx_active)
return;
} else {
- if (tty && (tty->stopped || tty->hw_stopped)) {
+ if (tty && (tty->flow.stopped || tty->hw_stopped)) {
tx_stop(info);
return;
}
@@ -1525,7 +1525,7 @@ static void mgslpc_flush_chars(struct tty_struct *tty)
if (mgslpc_paranoia_check(info, tty->name, "mgslpc_flush_chars"))
return;

- if (info->tx_count <= 0 || tty->stopped ||
+ if (info->tx_count <= 0 || tty->flow.stopped ||
tty->hw_stopped || !info->tx_buf)
return;

@@ -1594,7 +1594,7 @@ static int mgslpc_write(struct tty_struct * tty,
ret += c;
}
start:
- if (info->tx_count && !tty->stopped && !tty->hw_stopped) {
+ if (info->tx_count && !tty->flow.stopped && !tty->hw_stopped) {
spin_lock_irqsave(&info->lock, flags);
if (!info->tx_active)
tx_start(info, tty);
diff --git a/drivers/mmc/core/sdio_uart.c b/drivers/mmc/core/sdio_uart.c
index be4067281caa..dbcac2b7f2fe 100644
--- a/drivers/mmc/core/sdio_uart.c
+++ b/drivers/mmc/core/sdio_uart.c
@@ -439,7 +439,7 @@ static void sdio_uart_transmit_chars(struct sdio_uart_port *port)
tty = tty_port_tty_get(&port->port);

if (tty == NULL || !kfifo_len(xmit) ||
- tty->stopped || tty->hw_stopped) {
+ tty->flow.stopped || tty->hw_stopped) {
sdio_uart_stop_tx(port);
tty_kref_put(tty);
return;
diff --git a/drivers/net/caif/caif_serial.c b/drivers/net/caif/caif_serial.c
index fb3ca4e11fe5..3996cf7dc9ba 100644
--- a/drivers/net/caif/caif_serial.c
+++ b/drivers/net/caif/caif_serial.c
@@ -87,8 +87,8 @@ static void ldisc_tx_wakeup(struct tty_struct *tty);
static inline void update_tty_status(struct ser_device *ser)
{
ser->tty_status =
- ser->tty->stopped << 5 |
- ser->tty->flow_stopped << 3 |
+ ser->tty->flow.stopped << 5 |
+ ser->tty->flow.tco_stopped << 3 |
ser->tty->packet << 2;
}
static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
diff --git a/drivers/s390/char/tty3270.c b/drivers/s390/char/tty3270.c
index 307a80f85c07..1b68564799fa 100644
--- a/drivers/s390/char/tty3270.c
+++ b/drivers/s390/char/tty3270.c
@@ -1640,7 +1640,7 @@ tty3270_do_write(struct tty3270 *tp, struct tty_struct *tty,
int i_msg, i;

spin_lock_bh(&tp->view.lock);
- for (i_msg = 0; !tty->stopped && i_msg < count; i_msg++) {
+ for (i_msg = 0; !tty->flow.stopped && i_msg < count; i_msg++) {
if (tp->esc_state != 0) {
/* Continue escape sequence. */
tty3270_escape_sequence(tp, buf[i_msg]);
diff --git a/drivers/staging/fwserial/fwserial.c b/drivers/staging/fwserial/fwserial.c
index 1ee6382cafc4..4245532d2fe0 100644
--- a/drivers/staging/fwserial/fwserial.c
+++ b/drivers/staging/fwserial/fwserial.c
@@ -722,7 +722,7 @@ static int fwtty_tx(struct fwtty_port *port, bool drain)

/* try to write as many dma transactions out as possible */
n = -EAGAIN;
- while (!tty->stopped && !tty->hw_stopped &&
+ while (!tty->flow.stopped && !tty->hw_stopped &&
!test_bit(STOP_TX, &port->flags)) {
txn = kmem_cache_alloc(fwtty_txn_cache, GFP_ATOMIC);
if (!txn) {
diff --git a/drivers/tty/amiserial.c b/drivers/tty/amiserial.c
index ca48ce5a0862..a4b8876091d2 100644
--- a/drivers/tty/amiserial.c
+++ b/drivers/tty/amiserial.c
@@ -148,7 +148,7 @@ static __inline__ void rtsdtr_ctrl(int bits)
* ------------------------------------------------------------
* rs_stop() and rs_start()
*
- * This routines are called before setting or resetting tty->stopped.
+ * This routines are called before setting or resetting tty->flow.stopped.
* They enable or disable transmitter interrupts, as necessary.
* ------------------------------------------------------------
*/
@@ -309,7 +309,7 @@ static void transmit_chars(struct serial_state *info)
return;
}
if (info->xmit.head == info->xmit.tail
- || info->tport.tty->stopped
+ || info->tport.tty->flow.stopped
|| info->tport.tty->hw_stopped) {
info->IER &= ~UART_IER_THRI;
custom.intena = IF_TBE;
@@ -768,7 +768,7 @@ static void rs_flush_chars(struct tty_struct *tty)
unsigned long flags;

if (info->xmit.head == info->xmit.tail
- || tty->stopped
+ || tty->flow.stopped
|| tty->hw_stopped
|| !info->xmit.buf)
return;
@@ -812,7 +812,7 @@ static int rs_write(struct tty_struct * tty, const unsigned char *buf, int count
local_irq_restore(flags);

if (info->xmit.head != info->xmit.tail
- && !tty->stopped
+ && !tty->flow.stopped
&& !tty->hw_stopped
&& !(info->IER & UART_IER_THRI)) {
info->IER |= UART_IER_THRI;
diff --git a/drivers/tty/moxa.c b/drivers/tty/moxa.c
index 4d4f15b5cd29..847ad3dac107 100644
--- a/drivers/tty/moxa.c
+++ b/drivers/tty/moxa.c
@@ -1221,7 +1221,7 @@ static int moxa_write_room(struct tty_struct *tty)
{
struct moxa_port *ch;

- if (tty->stopped)
+ if (tty->flow.stopped)
return 0;
ch = tty->driver_data;
if (ch == NULL)
@@ -1374,7 +1374,7 @@ static int moxa_poll_port(struct moxa_port *p, unsigned int handle,
clear_bit(EMPTYWAIT, &p->statusflags);
tty_wakeup(tty);
}
- if (test_bit(LOWWAIT, &p->statusflags) && !tty->stopped &&
+ if (test_bit(LOWWAIT, &p->statusflags) && !tty->flow.stopped &&
MoxaPortTxQueue(p) <= WAKEUP_CHARS) {
clear_bit(LOWWAIT, &p->statusflags);
tty_wakeup(tty);
diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index 16a852ecbe8a..85271e109014 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -1118,7 +1118,7 @@ static int mxser_write(struct tty_struct *tty, const unsigned char *buf, int cou
total += c;
}

- if (info->xmit_cnt && !tty->stopped) {
+ if (info->xmit_cnt && !tty->flow.stopped) {
if (!tty->hw_stopped ||
(info->type == PORT_16550A) ||
(info->board->chip_flag)) {
@@ -1149,7 +1149,7 @@ static int mxser_put_char(struct tty_struct *tty, unsigned char ch)
info->xmit_head &= SERIAL_XMIT_SIZE - 1;
info->xmit_cnt++;
spin_unlock_irqrestore(&info->slock, flags);
- if (!tty->stopped) {
+ if (!tty->flow.stopped) {
if (!tty->hw_stopped ||
(info->type == PORT_16550A) ||
info->board->chip_flag) {
@@ -1169,7 +1169,7 @@ static void mxser_flush_chars(struct tty_struct *tty)
struct mxser_port *info = tty->driver_data;
unsigned long flags;

- if (info->xmit_cnt <= 0 || tty->stopped || !info->port.xmit_buf ||
+ if (info->xmit_cnt <= 0 || tty->flow.stopped || !info->port.xmit_buf ||
(tty->hw_stopped && info->type != PORT_16550A &&
!info->board->chip_flag))
return;
@@ -1917,7 +1917,7 @@ static void mxser_unthrottle(struct tty_struct *tty)
/*
* mxser_stop() and mxser_start()
*
- * This routines are called before setting or resetting tty->stopped.
+ * This routines are called before setting or resetting tty->flow.stopped.
* They enable or disable transmitter interrupts, as necessary.
*/
static void mxser_stop(struct tty_struct *tty)
@@ -1963,7 +1963,7 @@ static void mxser_set_termios(struct tty_struct *tty, struct ktermios *old_termi

/* Handle sw stopped */
if ((old_termios->c_iflag & IXON) && !I_IXON(tty)) {
- tty->stopped = 0;
+ tty->flow.stopped = 0;

if (info->board->chip_flag) {
spin_lock_irqsave(&info->slock, flags);
@@ -2175,7 +2175,7 @@ static void mxser_transmit_chars(struct tty_struct *tty, struct mxser_port *port
if (port->port.xmit_buf == NULL)
return;

- if (port->xmit_cnt <= 0 || tty->stopped ||
+ if (port->xmit_cnt <= 0 || tty->flow.stopped ||
(tty->hw_stopped &&
(port->type != PORT_16550A) &&
(!port->board->chip_flag))) {
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index c32318da5190..3566bb577eb0 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1289,7 +1289,7 @@ static void n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
}
}

- if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
+ if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
start_tty(tty);
process_echoes(tty);
}
@@ -1398,7 +1398,7 @@ static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
{
struct n_tty_data *ldata = tty->disc_data;

- if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
+ if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
start_tty(tty);
process_echoes(tty);
}
@@ -1427,7 +1427,7 @@ static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
if (c == STOP_CHAR(tty))
stop_tty(tty);
else if (c == START_CHAR(tty) ||
- (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
+ (tty->flow.stopped && !tty->flow.tco_stopped && I_IXANY(tty) &&
c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
c != SUSP_CHAR(tty))) {
start_tty(tty);
@@ -1797,7 +1797,7 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
* Fix tty hang when I_IXON(tty) is cleared, but the tty
* been stopped by STOP_CHAR(tty) before it.
*/
- if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
+ if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow.tco_stopped) {
start_tty(tty);
process_echoes(tty);
}
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 9b5d4ae5d8f2..017f28150a32 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -113,7 +113,7 @@ static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
struct tty_struct *to = tty->link;
unsigned long flags;

- if (tty->stopped)
+ if (tty->flow.stopped)
return 0;

if (c > 0) {
@@ -138,7 +138,7 @@ static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)

static int pty_write_room(struct tty_struct *tty)
{
- if (tty->stopped)
+ if (tty->flow.stopped)
return 0;
return tty_buffer_space_avail(tty->link->port);
}
diff --git a/drivers/tty/serial/arc_uart.c b/drivers/tty/serial/arc_uart.c
index 1a9444b6b57e..596217d10d5c 100644
--- a/drivers/tty/serial/arc_uart.c
+++ b/drivers/tty/serial/arc_uart.c
@@ -149,7 +149,7 @@ static unsigned int arc_serial_tx_empty(struct uart_port *port)
/*
* Driver internal routine, used by both tty(serial core) as well as tx-isr
* -Called under spinlock in either cases
- * -also tty->stopped has already been checked
+ * -also tty->flow.stopped has already been checked
* = by uart_start( ) before calling us
* = tx_ist checks that too before calling
*/
diff --git a/drivers/tty/serial/dz.c b/drivers/tty/serial/dz.c
index 4552742c3859..6d91e9b6284d 100644
--- a/drivers/tty/serial/dz.c
+++ b/drivers/tty/serial/dz.c
@@ -115,7 +115,7 @@ static void dz_out(struct dz_port *dport, unsigned offset, u16 value)
* rs_stop () and rs_start ()
*
* These routines are called before setting or resetting
- * tty->stopped. They enable or disable transmitter interrupts,
+ * tty->flow.stopped. They enable or disable transmitter interrupts,
* as necessary.
* ------------------------------------------------------------
*/
diff --git a/drivers/tty/synclink_gt.c b/drivers/tty/synclink_gt.c
index 5523cf7bd1c2..1555dccc28af 100644
--- a/drivers/tty/synclink_gt.c
+++ b/drivers/tty/synclink_gt.c
@@ -768,7 +768,7 @@ static int write(struct tty_struct *tty,
if (!info->tx_buf || (count > info->max_frame_size))
return -EIO;

- if (!count || tty->stopped || tty->hw_stopped)
+ if (!count || tty->flow.stopped || tty->hw_stopped)
return 0;

spin_lock_irqsave(&info->lock, flags);
@@ -889,7 +889,7 @@ static void flush_chars(struct tty_struct *tty)
return;
DBGINFO(("%s flush_chars entry tx_count=%d\n", info->device_name, info->tx_count));

- if (info->tx_count <= 0 || tty->stopped ||
+ if (info->tx_count <= 0 || tty->flow.stopped ||
tty->hw_stopped || !info->tx_buf)
return;

@@ -2241,7 +2241,7 @@ static void isr_txeom(struct slgt_info *info, unsigned short status)
else
#endif
{
- if (info->port.tty && (info->port.tty->stopped || info->port.tty->hw_stopped)) {
+ if (info->port.tty && (info->port.tty->flow.stopped || info->port.tty->hw_stopped)) {
tx_stop(info);
return;
}
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 5b5e99604989..9734be2eb00e 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -778,14 +778,14 @@ EXPORT_SYMBOL(tty_hung_up_p);
* but not always.
*
* Locking:
- * flow_lock
+ * flow.lock
*/

void __stop_tty(struct tty_struct *tty)
{
- if (tty->stopped)
+ if (tty->flow.stopped)
return;
- tty->stopped = 1;
+ tty->flow.stopped = true;
if (tty->ops->stop)
tty->ops->stop(tty);
}
@@ -794,9 +794,9 @@ void stop_tty(struct tty_struct *tty)
{
unsigned long flags;

- spin_lock_irqsave(&tty->flow_lock, flags);
+ spin_lock_irqsave(&tty->flow.lock, flags);
__stop_tty(tty);
- spin_unlock_irqrestore(&tty->flow_lock, flags);
+ spin_unlock_irqrestore(&tty->flow.lock, flags);
}
EXPORT_SYMBOL(stop_tty);

@@ -809,14 +809,14 @@ EXPORT_SYMBOL(stop_tty);
* start method is invoked and the line discipline woken.
*
* Locking:
- * flow_lock
+ * flow.lock
*/

void __start_tty(struct tty_struct *tty)
{
- if (!tty->stopped || tty->flow_stopped)
+ if (!tty->flow.stopped || tty->flow.tco_stopped)
return;
- tty->stopped = 0;
+ tty->flow.stopped = false;
if (tty->ops->start)
tty->ops->start(tty);
tty_wakeup(tty);
@@ -826,9 +826,9 @@ void start_tty(struct tty_struct *tty)
{
unsigned long flags;

- spin_lock_irqsave(&tty->flow_lock, flags);
+ spin_lock_irqsave(&tty->flow.lock, flags);
__start_tty(tty);
- spin_unlock_irqrestore(&tty->flow_lock, flags);
+ spin_unlock_irqrestore(&tty->flow.lock, flags);
}
EXPORT_SYMBOL(start_tty);

@@ -1172,7 +1172,7 @@ ssize_t redirected_tty_write(struct kiocb *iocb, struct iov_iter *iter)

int tty_send_xchar(struct tty_struct *tty, char ch)
{
- int was_stopped = tty->stopped;
+ bool was_stopped = tty->flow.stopped;

if (tty->ops->send_xchar) {
down_read(&tty->termios_rwsem);
@@ -3141,7 +3141,7 @@ struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
INIT_WORK(&tty->hangup_work, do_tty_hangup);
mutex_init(&tty->atomic_write_lock);
spin_lock_init(&tty->ctrl_lock);
- spin_lock_init(&tty->flow_lock);
+ spin_lock_init(&tty->flow.lock);
spin_lock_init(&tty->files_lock);
INIT_LIST_HEAD(&tty->tty_files);
INIT_WORK(&tty->SAK_work, do_SAK_work);
diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
index 41f7449d0464..07c88ccfb17a 100644
--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -846,20 +846,20 @@ int n_tty_ioctl_helper(struct tty_struct *tty, struct file *file,
return retval;
switch (arg) {
case TCOOFF:
- spin_lock_irq(&tty->flow_lock);
- if (!tty->flow_stopped) {
- tty->flow_stopped = 1;
+ spin_lock_irq(&tty->flow.lock);
+ if (!tty->flow.tco_stopped) {
+ tty->flow.tco_stopped = true;
__stop_tty(tty);
}
- spin_unlock_irq(&tty->flow_lock);
+ spin_unlock_irq(&tty->flow.lock);
break;
case TCOON:
- spin_lock_irq(&tty->flow_lock);
- if (tty->flow_stopped) {
- tty->flow_stopped = 0;
+ spin_lock_irq(&tty->flow.lock);
+ if (tty->flow.tco_stopped) {
+ tty->flow.tco_stopped = false;
__start_tty(tty);
}
- spin_unlock_irq(&tty->flow_lock);
+ spin_unlock_irq(&tty->flow.lock);
break;
case TCIOFF:
if (STOP_CHAR(tty) != __DISABLED_CHAR)
diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 303c198fbf5c..0eb523207828 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -587,7 +587,7 @@ int tty_port_close_start(struct tty_port *port,

if (tty_port_initialized(port)) {
/* Don't block on a stalled port, just pull the chain */
- if (tty->flow_stopped)
+ if (tty->flow.tco_stopped)
tty_driver_flush_buffer(tty);
if (port->closing_wait != ASYNC_CLOSING_WAIT_NONE)
tty_wait_until_sent(tty, port->closing_wait);
diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
index 5d2309742718..4b0d69042ceb 100644
--- a/drivers/tty/vt/keyboard.c
+++ b/drivers/tty/vt/keyboard.c
@@ -515,7 +515,7 @@ static void fn_hold(struct vc_data *vc)
* these routines are also activated by ^S/^Q.
* (And SCROLLOCK can also be set by the ioctl KDSKBLED.)
*/
- if (tty->stopped)
+ if (tty->flow.stopped)
start_tty(tty);
else
stop_tty(tty);
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index e5040bdadcd6..38c677fb6505 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -2888,7 +2888,7 @@ static int do_con_write(struct tty_struct *tty, const unsigned char *buf, int co

param.vc = vc;

- while (!tty->stopped && count) {
+ while (!tty->flow.stopped && count) {
int orig = *buf;
buf++;
n++;
@@ -3265,7 +3265,7 @@ static int con_put_char(struct tty_struct *tty, unsigned char ch)

static int con_write_room(struct tty_struct *tty)
{
- if (tty->stopped)
+ if (tty->flow.stopped)
return 0;
return 32768; /* No limit, really; we're not buffering */
}
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index d7ed00f1594e..7445c8fd88c0 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -428,7 +428,7 @@ int uart_resume_port(struct uart_driver *reg, struct uart_port *port);
static inline int uart_tx_stopped(struct uart_port *port)
{
struct tty_struct *tty = port->state->port.tty;
- if ((tty && tty->stopped) || port->hw_stopped)
+ if ((tty && tty->flow.stopped) || port->hw_stopped)
return 1;
return 0;
}
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 5aad2220266c..df3a69b2e1ea 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -243,20 +243,22 @@ struct tty_port {
#define TTY_PORT_KOPENED 5 /* device exclusively opened by
kernel */

-/*
- * Where all of the state associated with a tty is kept while the tty
- * is open. Since the termios state should be kept even if the tty
- * has been closed --- for things like the baud rate, etc --- it is
- * not stored here, but rather a pointer to the real state is stored
- * here. Possible the winsize structure should have the same
- * treatment, but (1) the default 80x24 is usually right and (2) it's
- * most often used by a windowing system, which will set the correct
- * size each time the window is created or resized anyway.
- * - TYT, 9/14/92
- */
-
struct tty_operations;

+/**
+ * struct tty_struct - state associated with a tty while open
+ *
+ * @flow.lock: lock for flow members
+ * @flow.stopped: tty stopped/started by tty_stop/tty_start
+ * @flow.tco_stopped: tty stopped/started by TCOOFF/TCOON ioctls (it has
+ * precedense over @flow.stopped)
+ * @flow.unused: alignment for Alpha, so that no members other than @flow.* are
+ * modified by the same 64b word store. The @flow's __aligned is
+ * there for the very same reason.
+ *
+ * All of the state associated with a tty while the tty is open. Persistent
+ * storage for tty devices is referenced here as @port in struct tty_port.
+ */
struct tty_struct {
int magic;
struct kref kref;
@@ -275,7 +277,6 @@ struct tty_struct {
struct rw_semaphore termios_rwsem;
struct mutex winsize_mutex;
spinlock_t ctrl_lock;
- spinlock_t flow_lock;
/* Termios values are protected by the termios rwsem */
struct ktermios termios, termios_locked;
char name[64];
@@ -288,9 +289,14 @@ struct tty_struct {
unsigned long flags;
int count;
struct winsize winsize; /* winsize_mutex */
- unsigned long stopped:1, /* flow_lock */
- flow_stopped:1,
- unused:BITS_PER_LONG - 2;
+
+ struct {
+ spinlock_t lock;
+ bool stopped;
+ bool tco_stopped;
+ unsigned long unused[0];
+ } __aligned(sizeof(unsigned long)) flow;
+
int hw_stopped;
unsigned long ctrl_status:8, /* ctrl_lock */
packet:1,
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index 2f719b471d52..653fa5af3a22 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -153,7 +153,7 @@
* This routine notifies the tty driver that it should stop
* outputting characters to the tty device.
*
- * Called with ->flow_lock held. Serialized with start() method.
+ * Called with ->flow.lock held. Serialized with start() method.
*
* Optional:
*
@@ -164,7 +164,7 @@
* This routine notifies the tty driver that it resume sending
* characters to the tty device.
*
- * Called with ->flow_lock held. Serialized with stop() method.
+ * Called with ->flow.lock held. Serialized with stop() method.
*
* Optional:
*
--
2.31.1