Fix tty_set_ldisc in tty_io.c so that tty->receive_room is
only cleared if actually changing line disciplines.
Without this fix a problem occurs when requesting the line
discipline to change to the same line discipline. In this case
tty->receive_room is cleared but ldisc->open() is not called
to set tty->receive_room back to a sane value. The result
is that tty->receive_room is stuck at 0 preventing the tty
flip buffer from passing receive data to the line discipline.
For example: a switch from N_TTY to N_TTY followed by
a select() call for read input results in data never being
received because tty->receive_room is stuck at zero.
A switch from N_TTY to N_TTY followed by
a read() call works because the read() call itself
sets tty->receive_room correctly (but select does not).
Previously (< 2.6.18) this was not a problem because
the tty flip buffer pushed data to the line discipline
without regard for tty->receive room.
Signed-off-by: Paul Fulghum <[email protected]>
--- a/drivers/char/tty_io.c 2007-04-25 22:08:32.000000000 -0500
+++ b/drivers/char/tty_io.c 2007-05-04 14:25:08.000000000 -0500
@@ -936,13 +936,6 @@ restart:
return -EINVAL;
/*
- * No more input please, we are switching. The new ldisc
- * will update this value in the ldisc open function
- */
-
- tty->receive_room = 0;
-
- /*
* Problem: What do we do if this blocks ?
*/
@@ -953,6 +946,13 @@ restart:
return 0;
}
+ /*
+ * No more input please, we are switching. The new ldisc
+ * will update this value in the ldisc open function
+ */
+
+ tty->receive_room = 0;
+
o_ldisc = tty->ldisc;
o_tty = tty->link;
-
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