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n_tty: Eliminate echo_commit memory barrier

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Use output_lock mutex as a memory barrier when storing echo_commit.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2013-06-15 10:04:25 -04:00 committed by Greg Kroah-Hartman
parent 17bd790740
commit 019ebdf9f2
1 changed files with 23 additions and 14 deletions
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37
drivers/tty/n_tty.c
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@ -638,21 +638,16 @@ break_out:
* 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;
mutex_unlock(&ldata->output_lock);
if (tty->ops->flush_chars)
tty->ops->flush_chars(tty);
}
static void commit_echoes(struct tty_struct *tty)
{
struct n_tty_data *ldata = tty->disc_data;
smp_mb();
mutex_lock(&ldata->output_lock);
ldata->echo_commit = ldata->echo_head;
process_echoes(tty);
__process_echoes(tty);
mutex_unlock(&ldata->output_lock);
if (tty->ops->flush_chars)
tty->ops->flush_chars(tty);
}
static void process_echoes(struct tty_struct *tty)
{
struct n_tty_data *ldata = tty->disc_data;
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);
}
/**