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TTY: serial, use ASYNCB_CLOSING in uart_close

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We need to move port->mutex locking after wait_until_sent in
uart_close (for rationale see next patches). But if we did it now, we
would introduce a race between close and open. This is exactly why
port->mutex is locked at the top of uart_close.

To avoid the race, we add ASYNCB_CLOSING to uart_close. Like every
other sane TTY driver. Thanks to tty_port_block_til_ready used in
uart_open we will have this for free. Then we can move the port->mutex
lock.

Also note that this will make the conversion to tty_port helpers
easier. They are currently handling ASYNC_CLOSING flag correctly.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Jiri Slaby 2011-08-25 15:12:04 +02:00 committed by Greg Kroah-Hartman
parent dfc97fcebd
commit 426929f8d3
1 changed files with 3 additions and 0 deletions
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3
drivers/tty/serial/serial_core.c
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@ -1288,6 +1288,7 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
* the line discipline to only process XON/XOFF characters by
* setting tty->closing.
*/
set_bit(ASYNCB_CLOSING, &port->flags);
tty->closing = 1;
spin_unlock_irqrestore(&port->lock, flags);
@ -1335,8 +1336,10 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
* Wake up anyone trying to open this port.
*/
clear_bit(ASYNCB_NORMAL_ACTIVE, &port->flags);
clear_bit(ASYNCB_CLOSING, &port->flags);
spin_unlock_irqrestore(&port->lock, flags);
wake_up_interruptible(&port->open_wait);
wake_up_interruptible(&port->close_wait);
done:
mutex_unlock(&port->mutex);