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Subject[PATCH] tty: Fix tcdrain hang due to tty chars_in_buffer errors
Date
If a tty driver's chars_in_buffer callback reports an error, the wait loop in
tty_wait_until_sent may never exit until its timeout. A tty device
disconnection will hangup the tty causing the tty_wait_until_sent loop to
wake-up, but if the subsequent call to chars_in_buffer reports an error
instead of zero, the loop will go back to sleep instead of exiting.

A process calling tcdrain will block indefinitely if it calls tcdrain when the
device is disconnected.

Signed-off-by: Jeff Harris <jeff_harris@kentrox.com>
---
drivers/char/tty_ioctl.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c
index ad6ba4e..306d52e 100644
--- a/drivers/char/tty_ioctl.c
+++ b/drivers/char/tty_ioctl.c
@@ -156,7 +156,7 @@ void tty_wait_until_sent(struct tty_struct *tty, long timeout)
if (!timeout)
timeout = MAX_SCHEDULE_TIMEOUT;
if (wait_event_interruptible_timeout(tty->write_wait,
- !tty_chars_in_buffer(tty), timeout) >= 0) {
+ tty_chars_in_buffer(tty) <= 0, timeout) >= 0) {
if (tty->ops->wait_until_sent)
tty->ops->wait_until_sent(tty, timeout);
}
@@ -332,7 +332,7 @@ void tty_termios_encode_baud_rate(struct ktermios *termios,
int iclose = ibaud/50, oclose = obaud/50;
int ibinput = 0;

- if (obaud == 0) /* CD dropped */
+ if (obaud == 0) /* CD dropped */
ibaud = 0; /* Clear ibaud to be sure */

termios->c_ispeed = ibaud;
--
1.5.5.1


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