If you driver implements "break on" and "break off" this ensures you
won't get multiple overlapping requests or requests in parallel. If
your driver has its own break handling then its still your problem as
the driver author.

Break is also now serialized against writes from user space properly but
no new guarantees are made driver level about writes from the line
discipline itself (eg flow control or echo)

Signed-off-by: Alan Cox redhat.com>

diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.18-rc4-mm2/drivers/char/tty_io.c linux-2.6.18-rc4-mm2/drivers/char/tty_io.c
--- linux.vanilla-2.6.18-rc4-mm2/drivers/char/tty_io.c 2006-08-21 14:18:53.000000000 +0100
+++ linux-2.6.18-rc4-mm2/drivers/char/tty_io.c 2006-08-21 15:16:04.000000000 +0100
@@ -2718,6 +2720,8 @@
* Locking:
* Called functions take tty_ldisc_lock
* current->signal->tty check is safe without locks
+ *
+ * FIXME: may race normal receive processing
*/