[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>

2 files changed, 0 insertions, 13 deletions

diff --git a/drivers/serial/crisv10.c b/drivers/serial/crisv10.c
index 89700141f87e..5cacc5e74a92 100644
--- a/drivers/serial/crisv10.c
+++ b/drivers/serial/crisv10.c
@@ -2573,12 +2573,6 @@ static void flush_to_flip_buffer(struct e100_serial *info)
 
         DFLIP(
           if (1) {
-
-                  if (test_bit(TTY_DONT_FLIP, &tty->flags)) {
-                          DEBUG_LOG(info->line, "*** TTY_DONT_FLIP set flip.count %i ***\n", tty->flip.count);
-                          DEBUG_LOG(info->line, "*** recv_cnt %i\n", info->recv_cnt);
-                  } else {
-                  }
                   DEBUG_LOG(info->line, "*** rxtot %i\n", info->icount.rx);
                   DEBUG_LOG(info->line, "ldisc %lu\n", tty->ldisc.chars_in_buffer(tty));
                   DEBUG_LOG(info->line, "room  %lu\n", tty->ldisc.receive_room(tty));
diff --git a/drivers/serial/jsm/jsm_tty.c b/drivers/serial/jsm/jsm_tty.c
index 7d823705193c..f8262e6ad8d3 100644
--- a/drivers/serial/jsm/jsm_tty.c
+++ b/drivers/serial/jsm/jsm_tty.c
@@ -589,13 +589,6 @@ void jsm_input(struct jsm_channel *ch)
         ld = tty_ldisc_ref(tp);
 
         /*
-         * If the DONT_FLIP flag is on, don't flush our buffer, and act
-         * like the ld doesn't have any space to put the data right now.
-         */
-        if (test_bit(TTY_DONT_FLIP, &tp->flags))
-                len = 0;
-
-        /*
          * If we were unable to get a reference to the ld,
          * don't flush our buffer, and act like the ld doesn't
          * have any space to put the data right now.