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Commit 019ebdf9 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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n_tty: Eliminate echo_commit memory barrier 



Use output_lock mutex as a memory barrier when storing echo_commit.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 17bd7907

drivers/tty/n_tty.c

+20 −11
Original line number Diff line number Diff line
@@ -638,21 +638,16 @@ static ssize_t process_output_block(struct tty_struct *tty, 
 *	are prioritized.  Also, when control characters are echoed with a

 *	prefixed "^", the pair is treated atomically and thus not separated.

 *

 *	Locking: output_lock to protect column state and space left

 *	Locking: callers must hold output_lock

 */



static void process_echoes(struct tty_struct *tty)

static void __process_echoes(struct tty_struct *tty)

{

	struct n_tty_data *ldata = tty->disc_data;

	int	space, nr;

	size_t tail;

	unsigned char c;



	if (ldata->echo_commit == ldata->echo_tail)

		return;



	mutex_lock(&ldata->output_lock);



	space = tty_write_room(tty);



	tail = ldata->echo_tail;
@@ -772,20 +767,34 @@ static void process_echoes(struct tty_struct *tty) 
	}



	ldata->echo_tail = tail;

}



static void commit_echoes(struct tty_struct *tty)

{

	struct n_tty_data *ldata = tty->disc_data;



	mutex_lock(&ldata->output_lock);

	ldata->echo_commit = ldata->echo_head;

	__process_echoes(tty);

	mutex_unlock(&ldata->output_lock);



	if (tty->ops->flush_chars)

		tty->ops->flush_chars(tty);

}



static void commit_echoes(struct tty_struct *tty)

static void process_echoes(struct tty_struct *tty)

{

	struct n_tty_data *ldata = tty->disc_data;



	smp_mb();

	ldata->echo_commit = ldata->echo_head;

	process_echoes(tty);

	if (!L_ECHO(tty) || ldata->echo_commit == ldata->echo_tail)

		return;



	mutex_lock(&ldata->output_lock);

	__process_echoes(tty);

	mutex_unlock(&ldata->output_lock);



	if (tty->ops->flush_chars)

		tty->ops->flush_chars(tty);

}



/**