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serial: core: Privatize tty->hw_stopped

Browse source 
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@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2014-09-10 15:06:26 -04:00 committed by Greg Kroah-Hartman
parent 317c136020
commit d01f4d181c
3 changed files with 22 additions and 23 deletions
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14
drivers/tty/serial/bfin_uart.c
View file

@ -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;
}

28
drivers/tty/serial/serial_core.c
View file

@ -95,7 +95,7 @@ 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);
}
@ -181,10 +181,11 @@ 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);
}
@ -949,7 +950,7 @@ 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);
@ -1295,7 +1296,7 @@ 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;
@ -1303,7 +1304,7 @@ 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);
}
@ -1311,7 +1312,7 @@ 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);
@ -2788,23 +2789,20 @@ 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);
}
}

3
include/linux/serial_core.h
View file

@ -197,6 +197,7 @@ 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 */
@ -357,7 +358,7 @@ 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;
}