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serial: core: Fix port count when uart_open() errors 

A port count mismatch occurs if mutex_lock_interruptible()
exits uart_open() and the port has already been opened. This may
prematurely close a port on an open tty. Since uart_close() is _always_
called if uart_open() fails, the port count must be corrected if errors
occur.

Always increment the port count in uart_open(), regardless of errors;
always decrement the port count in uart_close(). Note that
tty_port_close_start() decrements the port count when uart_open()
was successful.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
hifive-unleashed-5.1
Peter Hurley 2014-10-16 16:54:27 -04:00 committed by Greg Kroah-Hartman
parent 64dbee3105
commit 91b32f5413
1 changed files with 15 additions and 10 deletions
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25
drivers/tty/serial/serial_core.c
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@ -1338,8 +1338,16 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
struct uart_port *uport;
unsigned long flags;
if (!state)
if (!state) {
struct uart_driver *drv = tty->driver->driver_state;
state = drv->state + tty->index;
port = &state->port;
spin_lock_irq(&port->lock);
--port->count;
spin_unlock_irq(&port->lock);
return;
}
uport = state->uart_port;
port = &state->port;
@ -1556,6 +1564,10 @@ static int uart_open(struct tty_struct *tty, struct file *filp)
pr_debug("uart_open(%d) called\n", line);
spin_lock_irq(&port->lock);
++port->count;
spin_unlock_irq(&port->lock);
/*
* We take the semaphore here to guarantee that we won't be re-entered
* while allocating the state structure, or while we request any IRQs
@ -1568,17 +1580,11 @@ static int uart_open(struct tty_struct *tty, struct file *filp)
goto end;
}
port->count++;
if (!state->uart_port || state->uart_port->flags & UPF_DEAD) {
retval = -ENXIO;
goto err_dec_count;
goto err_unlock;
}
/*
* Once we set tty->driver_data here, we are guaranteed that
* uart_close() will decrement the driver module use count.
* Any failures from here onwards should not touch the count.
*/
tty->driver_data = state;
state->uart_port->state = state;
state->port.low_latency =
@ -1599,8 +1605,7 @@ static int uart_open(struct tty_struct *tty, struct file *filp)
end:
return retval;
err_dec_count:
port->count--;
err_unlock:
mutex_unlock(&port->mutex);
goto end;
}