From: Paul Fulghum 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 Cc: Alan Cox Signed-off-by: Andrew Morton --- drivers/char/tty_io.c | 14 +++++++------- 1 files changed, 7 insertions(+), 7 deletions(-) diff -puN drivers/char/tty_io.c~tty_set_ldisc-receive_room-fix drivers/char/tty_io.c --- a/drivers/char/tty_io.c~tty_set_ldisc-receive_room-fix +++ a/drivers/char/tty_io.c @@ -934,13 +934,6 @@ 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 ? */ @@ -951,6 +944,13 @@ 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; _