[src/trunk]: src/sys/kern Fix various bogus things:

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/55af97365b84
branches:  trunk
changeset: 769803:55af97365b84
user:      christos <christos%NetBSD.org@localhost>
date:      Fri Sep 23 23:57:06 2011 +0000

description:
Fix various bogus things:
- Don't use TTYHOG - 1, you can use the last byte in the ring buffer.
- Don't put unnecessary if statements around the code. The loop invariant
  is that if you reach the top of the loop, cc == 0.
- Remove cast to (void *).
- Check result of b_to_q and adjust cc.
- Explain what the TTYHOG - 2 code tried to do, and do it right.

diffstat:

 sys/kern/tty_pty.c |  92 ++++++++++++++++++++++++++++-------------------------
 1 files changed, 48 insertions(+), 44 deletions(-)

diffs (133 lines):

diff -r 913e6047e3ab -r 55af97365b84 sys/kern/tty_pty.c
--- a/sys/kern/tty_pty.c        Fri Sep 23 23:02:23 2011 +0000
+++ b/sys/kern/tty_pty.c        Fri Sep 23 23:57:06 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tty_pty.c,v 1.129 2011/07/26 13:14:18 yamt Exp $       */
+/*     $NetBSD: tty_pty.c,v 1.130 2011/09/23 23:57:06 christos Exp $   */
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -37,7 +37,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tty_pty.c,v 1.129 2011/07/26 13:14:18 yamt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tty_pty.c,v 1.130 2011/09/23 23:57:06 christos Exp $");
 
 #include "opt_ptm.h"
 
@@ -701,30 +701,30 @@
        if (pti->pt_flags & PF_REMOTE) {
                if (tp->t_canq.c_cc)
                        goto block;
-               while (uio->uio_resid > 0 && tp->t_canq.c_cc < TTYHOG - 1) {
-                       if (cc == 0) {
-                               cc = min(uio->uio_resid, BUFSIZ);
-                               cc = min(cc, TTYHOG - 1 - tp->t_canq.c_cc);
-                               cp = locbuf;
-                               mutex_spin_exit(&tty_lock);
-                               error = uiomove((void *)cp, cc, uio);
-                               if (error != 0)
-                                       return error;
-                               mutex_spin_enter(&tty_lock);
-                               /* check again for safety */
-                               if (!ISSET(tp->t_state, TS_ISOPEN)) {
-                                       /*
-                                        * adjust for data copied in but not
-                                        * written
-                                        */
-                                       uio->uio_resid += cc;
-                                       error = EIO;
-                                       goto out;
-                               }
+               while (uio->uio_resid > 0 && tp->t_canq.c_cc < TTYHOG) {
+                       cc = min(uio->uio_resid, BUFSIZ);
+                       cc = min(cc, TTYHOG - tp->t_canq.c_cc);
+                       cp = locbuf;
+                       mutex_spin_exit(&tty_lock);
+                       error = uiomove(cp, cc, uio);
+                       if (error != 0)
+                               return error;
+                       mutex_spin_enter(&tty_lock);
+                       /* check again for safety */
+                       if (!ISSET(tp->t_state, TS_ISOPEN)) {
+                               /*
+                                * adjust for data copied in but not
+                                * written
+                                */
+                               uio->uio_resid += cc;
+                               error = EIO;
+                               goto out;
                        }
-                       if (cc)
-                               (void) b_to_q(cp, cc, &tp->t_canq);
-                       cc = 0;
+                       if (cc) {
+                               cc = b_to_q(cp, cc, &tp->t_outq);
+                               if (cc > 0)
+                                       goto block;
+                       }
                }
                (void) putc(0, &tp->t_canq);
                ttwakeup(tp);
@@ -733,29 +733,34 @@
                goto out;
        }
        while (uio->uio_resid > 0) {
-               if (cc == 0) {
-                       cc = min(uio->uio_resid, BUFSIZ);
-                       cp = locbuf;
-                       mutex_spin_exit(&tty_lock);
-                       error = uiomove((void *)cp, cc, uio);
-                       if (error != 0)
-                               return error;
-                       mutex_spin_enter(&tty_lock);
-                       /* check again for safety */
-                       if (!ISSET(tp->t_state, TS_ISOPEN)) {
-                               /* adjust for data copied in but not written */
-                               uio->uio_resid += cc;
-                               error = EIO;
-                               goto out;
-                       }
+               cc = min(uio->uio_resid, BUFSIZ);
+               cp = locbuf;
+               mutex_spin_exit(&tty_lock);
+               error = uiomove(cp, cc, uio);
+               if (error != 0)
+                       return error;
+               mutex_spin_enter(&tty_lock);
+               /* check again for safety */
+               if (!ISSET(tp->t_state, TS_ISOPEN)) {
+                       /* adjust for data copied in but not written */
+                       uio->uio_resid += cc;
+                       error = EIO;
+                       goto out;
                }
                while (cc > 0) {
-                       if ((tp->t_rawq.c_cc + tp->t_canq.c_cc) >= TTYHOG - 2 &&
-                          (tp->t_canq.c_cc > 0 || !ISSET(tp->t_lflag, ICANON))) {
+                       int used = tp->t_rawq.c_cc + tp->t_canq.c_cc;
+                       int canon = ISSET(tp->t_lflag, ICANON) ? 1 : 0;
+                       /*
+                        * We need space for 2 characters if canonical
+                        * because we might need to print ^C
+                        */
+                       if (used >= (TTYHOG - canon) &&
+                          (tp->t_canq.c_cc > 0 || !canon)) {
                                cv_broadcast(&tp->t_rawcv);
                                goto block;
                        }
-                       /* XXX - should change l_rint to be called with lock
+                       /*
+                        * XXX - should change l_rint to be called with lock
                         *       see also tty.c:ttyinput_wlock()
                         */
                        mutex_spin_exit(&tty_lock);
@@ -764,7 +769,6 @@
                        cnt++;
                        cc--;
                }
-               cc = 0;
        }
        error = 0;
        goto out;