Messages in this thread Patch in this message | | | Date | Wed, 6 Feb 2008 15:51:17 -0800 | From | Greg KH <> | Subject | [patch 11/73] tty: fix logic change introduced by wait_event_interruptible_timeout() |
| |
2.6.23-stable review patch. If anyone has any objections, please let us know. ------------------ From: "Cory T. Tusar" <ctusar@videon-central.com>
patch db99247ac68fc352100090ad7704fb5efb9327b6 in mainline.
Commit 5a52bd4a2dcb570333ce6fe2e16cd311650dbdc8 introduced a subtle logic change in tty_wait_until_sent(). The original version would only error out of the 'do { ... } while (timeout)' loop if signal_pending() evaluated to true; a timeout or break due to an empty buffer would fall out of the loop and into the tty->driver->wait_until_sent handling. The current implementation will error out on either a pending signal or an empty buffer, falling through to the tty->driver->wait_until_sent handling only on a timeout.
The ->wait_until_sent() will not be reached if the buffer empties before timeout jiffies have elapsed. This behavior differs from that prior to commit 5a52bd4a2dcb570333ce6fe2e16cd311650dbdc8.
I turned this up while using a little serial download utility to bootstrap an ARM-based eval board. The util worked fine on 2.6.22.x, but consistently failed on 2.6.23.x. Once I'd determined that, I narrowed things down with git bisect, and found the above difference in logic in tty_wait_until_sent() by inspection.
This change reverts the logic flow in tty_wait_until_sent() to match that prior to the aforementioned commit.
Signed-off-by: Cory T. Tusar <ctusar@videon-central.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Acked-by: Jiri Slaby <jirislaby@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/char/tty_ioctl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/char/tty_ioctl.c +++ b/drivers/char/tty_ioctl.c @@ -62,7 +62,7 @@ void tty_wait_until_sent(struct tty_stru if (!timeout) timeout = MAX_SCHEDULE_TIMEOUT; if (wait_event_interruptible_timeout(tty->write_wait, - !tty->driver->chars_in_buffer(tty), timeout)) + !tty->driver->chars_in_buffer(tty), timeout) < 0) return; if (tty->driver->wait_until_sent) tty->driver->wait_until_sent(tty, timeout); --
| |