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[PATCH] remove TTY_DONT_FLIP

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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>
This commit is contained in:
Paul Fulghum
2006-06-28 04:26:47 -07:00
committed by Linus Torvalds
parent e0ac4761fa
commit 817d6d3bce
9 changed files with 7 additions and 42 deletions
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15
drivers/char/tty_io.c
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@@ -784,11 +784,8 @@ restart:
}
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 @@ static void release_dev(struct file * filp)
* 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 @@ static void flush_to_ldisc(void *private_)
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 @@ static void flush_to_ldisc(void *private_)
tty_buffer_free(tty, tbuf);
}
spin_unlock_irqrestore(&tty->buf.lock, flags);
out:
tty_ldisc_deref(disc);
}