[PATCH] remove TTY_DONT_FLIP
Remove TTY_DONT_FLIP tty flag. This flag was introduced in 2.1.X kernels
to prevent the N_TTY line discipline functions read_chan() and
n_tty_receive_buf() from running at the same time. 2.2.15 introduced
tty->read_lock to protect access to the N_TTY read buffer, which is the
only state requiring protection between these two functions.
The current TTY_DONT_FLIP implementation is broken for SMP, and is not
universally honored by drivers that send data directly to the line
discipline receive_buf function.
Because TTY_DONT_FLIP is not necessary, is broken in implementation, and is
not universally honored, it is removed.
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/char/mxser.c b/drivers/char/mxser.c
index 645d9d7..72cfd09 100644
--- a/drivers/char/mxser.c
+++ b/drivers/char/mxser.c
@@ -996,7 +996,6 @@
info->session = current->signal->session;
info->pgrp = process_group(current);
- clear_bit(TTY_DONT_FLIP, &tty->flags);
/*
status = mxser_get_msr(info->base, 0, info->port);
diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index b9371d5..603b9ad 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -1132,7 +1132,7 @@
* buffer, and once to drain the space from the (physical) beginning of
* the buffer to head pointer.
*
- * Called under the tty->atomic_read_lock sem and with TTY_DONT_FLIP set
+ * Called under the tty->atomic_read_lock sem
*
*/
@@ -1271,7 +1271,6 @@
}
add_wait_queue(&tty->read_wait, &wait);
- set_bit(TTY_DONT_FLIP, &tty->flags);
while (nr) {
/* First test for status change. */
if (tty->packet && tty->link->ctrl_status) {
@@ -1315,9 +1314,7 @@
break;
}
n_tty_set_room(tty);
- clear_bit(TTY_DONT_FLIP, &tty->flags);
timeout = schedule_timeout(timeout);
- set_bit(TTY_DONT_FLIP, &tty->flags);
continue;
}
__set_current_state(TASK_RUNNING);
@@ -1394,7 +1391,6 @@
if (time)
timeout = time;
}
- clear_bit(TTY_DONT_FLIP, &tty->flags);
mutex_unlock(&tty->atomic_read_lock);
remove_wait_queue(&tty->read_wait, &wait);
diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index 9b5a2c0..0c17f61 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -101,7 +101,7 @@
*
* FIXME: Our pty_write method is called with our ldisc lock held but
* not our partners. We can't just take the other one blindly without
- * risking deadlocks. There is also the small matter of TTY_DONT_FLIP
+ * risking deadlocks.
*/
static int pty_write(struct tty_struct * tty, const unsigned char *buf, int count)
{
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index bd74e82..b846d87 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -784,11 +784,8 @@
}
clear_bit(TTY_LDISC, &tty->flags);
- clear_bit(TTY_DONT_FLIP, &tty->flags);
- if (o_tty) {
+ if (o_tty)
clear_bit(TTY_LDISC, &o_tty->flags);
- clear_bit(TTY_DONT_FLIP, &o_tty->flags);
- }
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
/*
@@ -1955,7 +1952,6 @@
* race with the set_ldisc code path.
*/
clear_bit(TTY_LDISC, &tty->flags);
- clear_bit(TTY_DONT_FLIP, &tty->flags);
cancel_delayed_work(&tty->buf.work);
/*
@@ -2784,13 +2780,6 @@
if (disc == NULL) /* !TTY_LDISC */
return;
- if (test_bit(TTY_DONT_FLIP, &tty->flags)) {
- /*
- * Do it after the next timer tick:
- */
- schedule_delayed_work(&tty->buf.work, 1);
- goto out;
- }
spin_lock_irqsave(&tty->buf.lock, flags);
while((tbuf = tty->buf.head) != NULL) {
while ((count = tbuf->commit - tbuf->read) != 0) {
@@ -2809,7 +2798,7 @@
tty_buffer_free(tty, tbuf);
}
spin_unlock_irqrestore(&tty->buf.lock, flags);
-out:
+
tty_ldisc_deref(disc);
}
