serial: Test for no tx data on tx restart
authorPeter Hurley <peter@hurleysoftware.com>
Sun, 6 Jul 2014 15:29:52 +0000 (11:29 -0400)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 10 Jul 2014 23:31:34 +0000 (16:31 -0700)
commitc557d392fbf5badd693ea1946a4317c87a26a716
tree10b1369df578934fa8d43fbef7c69fb523ac5ab9
parentcd3de83f147601356395b57a8673e9c5ff1e59d1
serial: Test for no tx data on tx restart

Commit 717f3bbab3c7628736ef738fdbf3d9a28578c26c,
'serial_core: Fix conditional start_tx on ring buffer not empty'
exposes an incorrect assumption in several drivers' start_tx methods;
the tx ring buffer can, in fact, be empty when restarting tx while
performing flow control.

Affected drivers:
sunsab.c
ip22zilog.c
pmac_zilog.c
sunzilog.c
m32r_sio.c
imx.c

Other in-tree serial drivers either are not affected or already
test for empty tx ring buffer before transmitting.

Test for empty tx ring buffer in start_tx() method, after transmitting
x_char (if applicable).

Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Seth Bollinger <sethb@digi.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org> # 3.15
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/tty/serial/imx.c
drivers/tty/serial/ip22zilog.c
drivers/tty/serial/m32r_sio.c
drivers/tty/serial/pmac_zilog.c
drivers/tty/serial/sunsab.c
drivers/tty/serial/sunzilog.c