tty: cumulate and document tty_struct::flow* members

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 c545b66 (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 <[email protected]> Cc: "David S. Miller" <[email protected]> Cc: Jakub Kicinski <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: Ulf Hansson <[email protected]> Cc: Heiko Carstens <[email protected]> Cc: Vasily Gorbik <[email protected]> Cc: Christian Borntraeger <[email protected]> Cc: Shawn Guo <[email protected]> Cc: Sascha Hauer <[email protected]> Cc: Vineet Gupta <[email protected]> Cc: "Maciej W. Rozycki" <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]>
niw · May 13, 2021 · 6e94dbc · 6e94dbc
1 parent 0f3dcf3
commit 6e94dbc
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Showing 22 changed files with 83 additions and 77 deletions.
diff --git 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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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)