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Date: Wed, 10 Sep 2014 15:06:26 -0400
From: Peter Hurley <peter@...leysoftware.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Slaby <jslaby@...e.cz>,
One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
Peter Hurley <peter@...leysoftware.com>
Subject: [PATCH v2 04/14] serial: core: Privatize tty->hw_stopped
tty->hw_stopped is not used by the tty core and is thread-unsafe;
hw_stopped is a member of a bitfield whose fields are updated
non-atomically and no lock is suitable for serializing updates.
Replace serial core usage of tty->hw_stopped with uport->hw_stopped.
Use int storage which works around Alpha EV4/5 non-atomic byte storage,
since uart_port uses different locks to protect certain fields within the
structure.
Signed-off-by: Peter Hurley <peter@...leysoftware.com>
---
drivers/tty/serial/bfin_uart.c | 14 +++++++-------
drivers/tty/serial/serial_core.c | 28 +++++++++++++---------------
include/linux/serial_core.h | 3 ++-
3 files changed, 22 insertions(+), 23 deletions(-)
diff --git a/drivers/tty/serial/bfin_uart.c b/drivers/tty/serial/bfin_uart.c
index dec0fd7..fc9fbf3 100644
--- a/drivers/tty/serial/bfin_uart.c
+++ b/drivers/tty/serial/bfin_uart.c
@@ -108,22 +108,22 @@ static void bfin_serial_set_mctrl(struct uart_port *port, unsigned int mctrl)
static irqreturn_t bfin_serial_mctrl_cts_int(int irq, void *dev_id)
{
struct bfin_serial_port *uart = dev_id;
- unsigned int status = bfin_serial_get_mctrl(&uart->port);
+ struct uart_port *uport = &uart->port;
+ unsigned int status = bfin_serial_get_mctrl(uport);
#ifdef CONFIG_SERIAL_BFIN_HARD_CTSRTS
- struct tty_struct *tty = uart->port.state->port.tty;
UART_CLEAR_SCTS(uart);
- if (tty->hw_stopped) {
+ if (uport->hw_stopped) {
if (status) {
- tty->hw_stopped = 0;
- uart_write_wakeup(&uart->port);
+ uport->hw_stopped = 0;
+ uart_write_wakeup(uport);
}
} else {
if (!status)
- tty->hw_stopped = 1;
+ uport->hw_stopped = 1;
}
#endif
- uart_handle_cts_change(&uart->port, status & TIOCM_CTS);
+ uart_handle_cts_change(uport, status & TIOCM_CTS);
return IRQ_HANDLED;
}
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 3c62b3f..1f52a7d 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -94,7 +94,7 @@ static void __uart_start(struct tty_struct *tty)
struct uart_state *state = tty->driver_data;
struct uart_port *port = state->uart_port;
- if (!tty->stopped && !tty->hw_stopped)
+ if (!uart_tx_stopped(port))
port->ops->start_tx(port);
}
@@ -180,10 +180,11 @@ static int uart_port_startup(struct tty_struct *tty, struct uart_state *state,
}
spin_lock_irq(&uport->lock);
- if (uart_cts_enabled(uport)) {
- if (!(uport->ops->get_mctrl(uport) & TIOCM_CTS))
- tty->hw_stopped = 1;
- }
+ if (uart_cts_enabled(uport) &&
+ !(uport->ops->get_mctrl(uport) & TIOCM_CTS))
+ uport->hw_stopped = 1;
+ else
+ uport->hw_stopped = 0;
spin_unlock_irq(&uport->lock);
}
@@ -944,7 +945,7 @@ static int uart_get_lsr_info(struct tty_struct *tty,
*/
if (uport->x_char ||
((uart_circ_chars_pending(&state->xmit) > 0) &&
- !tty->stopped && !tty->hw_stopped))
+ !uart_tx_stopped(uport)))
result &= ~TIOCSER_TEMT;
return put_user(result, value);
@@ -1290,7 +1291,7 @@ static void uart_set_termios(struct tty_struct *tty,
/*
* If the port is doing h/w assisted flow control, do nothing.
- * We assume that tty->hw_stopped has never been set.
+ * We assume that port->hw_stopped has never been set.
*/
if (uport->flags & UPF_HARD_FLOW)
return;
@@ -1298,7 +1299,7 @@ static void uart_set_termios(struct tty_struct *tty,
/* Handle turning off CRTSCTS */
if ((old_termios->c_cflag & CRTSCTS) && !(cflag & CRTSCTS)) {
spin_lock_irqsave(&uport->lock, flags);
- tty->hw_stopped = 0;
+ uport->hw_stopped = 0;
__uart_start(tty);
spin_unlock_irqrestore(&uport->lock, flags);
}
@@ -1306,7 +1307,7 @@ static void uart_set_termios(struct tty_struct *tty,
else if (!(old_termios->c_cflag & CRTSCTS) && (cflag & CRTSCTS)) {
spin_lock_irqsave(&uport->lock, flags);
if (!(uport->ops->get_mctrl(uport) & TIOCM_CTS)) {
- tty->hw_stopped = 1;
+ uport->hw_stopped = 1;
uport->ops->stop_tx(uport);
}
spin_unlock_irqrestore(&uport->lock, flags);
@@ -2776,23 +2777,20 @@ EXPORT_SYMBOL_GPL(uart_handle_dcd_change);
*/
void uart_handle_cts_change(struct uart_port *uport, unsigned int status)
{
- struct tty_port *port = &uport->state->port;
- struct tty_struct *tty = port->tty;
-
lockdep_assert_held_once(&uport->lock);
uport->icount.cts++;
if (uart_cts_enabled(uport)) {
- if (tty->hw_stopped) {
+ if (uport->hw_stopped) {
if (status) {
- tty->hw_stopped = 0;
+ uport->hw_stopped = 0;
uport->ops->start_tx(uport);
uart_write_wakeup(uport);
}
} else {
if (!status) {
- tty->hw_stopped = 1;
+ uport->hw_stopped = 1;
uport->ops->stop_tx(uport);
}
}
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index bc70048..677a97c 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -195,6 +195,7 @@ struct uart_port {
#define UPSTAT_CTS_ENABLE ((__force upstat_t) (1 << 0))
#define UPSTAT_DCD_ENABLE ((__force upstat_t) (1 << 1))
+ int hw_stopped; /* sw-assisted CTS flow state */
unsigned int mctrl; /* current modem ctrl settings */
unsigned int timeout; /* character-based timeout */
unsigned int type; /* port type */
@@ -353,7 +354,7 @@ 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->stopped || tty->hw_stopped)
+ if (tty->stopped || port->hw_stopped)
return 1;
return 0;
}
--
2.1.0
--
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