Hi!
> (Wow, that was a lot of text for this little thing... 8-)
Yep.
> --- drivers/char/n_tty.c.orig Tue Jan 29 18:26:54 2002
> +++ drivers/char/n_tty.c Thu Jan 31 02:28:51 2002
> @@ -18,11 +18,35 @@
> * This file may be redistributed under the terms of the GNU General Public
> * License.
> *
> + * 2002/01/29 Fixed & Extended VMIN handling.
> + * Patch By: Robert White <rwhite@pobox.com>
> + * Problem: Where VTIME == 0 and VMIN > nr durring read,
> + * read would block for characters it couldn't possibly return.
> + * Reading variable sized blocks required multiple syscalls
> + * (termio set followed by read) or reliance on timeout.
> + * or multiple reads of fragments. For large reads n_tty
> + * was not capible of returning more than 255 bytes (bad
> + * for performance of any serial protocols. c.f. Z-MODEM etc)
> + * Fix: if VMIN > nr, use nr to set minimum instead. (adjust down)
> + * Extension: if VMIN == 255, always set minimum to nr (up OR down)
> + * (Fix and Extension apply to each read call, VMIN itself is not adjusted)
> + * Consider: (w/8 or 1500 chars from device to be delivered respectively)
> + * VMIN=30, VTIME=0, read(fd,buf,8);
> + * Old: read never returns, New: returns immed on 8th char
> + * VMIN=30, VTIME=200, read(fd,buf,8);
> + * Old: return in 20 seconds, New: returns immed on 8th char
> + * VMIN=255, VTIME=0, read(fd,buf,1500);
> + * Old: 5 reads of ~255 then deadlock, New: 1 read to complete
> + * VMIN=255, VTIME>0, read(fd,buf,1500);
> + * Old: 5 reads then timout for remainder, New: 1 read
> + * or more depending timeout occurences)
> + *
> * Reduced memory usage for older ARM systems - Russell King
> *
> * 2000/01/20 Fixed SMP locking on put_tty_queue using bits of
> * the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
> * who actually finally proved there really was a race.
> + *
> */
>
> #include <linux/types.h>
> @@ -974,6 +998,11 @@
> if (!tty->icanon) {
> time = (HZ / 10) * TIME_CHAR(tty);
> minimum = MIN_CHAR(tty);
> + /* Added rwhite@pobox.com Jan 29, 2002 */
> + if ((minimum == 255) || (minimum > nr)) {
> + minimum = nr;
> + }
> + /* End Addition */
> if (minimum) {
> if (time)
> tty->minimum_to_wake = 1;
Kill comments who added it. Imagine if everyone done that.
> @@ -1021,6 +1050,16 @@
> if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
> ((minimum - (b - buf)) >= 1))
> tty->minimum_to_wake = (minimum - (b - buf));
> +
> + /* Added rwhite@pobox.com Jan 29, 2002 */
> + // minimum and therefore minimum_to_wake could be much larger
> + // than the actual buffer here, so...
> + if (tty->minimum_to_wake >= TTY_FLIPBUF_SIZE) {
> + // Flow Control would deadlock at (N_TTY_BUF_SIZE -
> TTY_THRESHOLD_THROTTLE)
> + // using TTY_FLIPBUF_SIZE-1 is safe and likely linear/streaming.
> + tty->minimum_to_wake = TTY_FLIPBUF_SIZE - 1;
> + }
> + /* End Addition */
No C++ comments, please.
Pavel
-- (about SSSCA) "I don't say this lightly. However, I really think that the U.S. no longer is classifiable as a democracy, but rather as a plutocracy." --hpa - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Sun Jun 30 2002 - 22:00:11 EST