/*-
 * (MPSAFE)
 *
 * Copyright (c) 1982, 1986, 1990, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)tty.c       8.8 (Berkeley) 1/21/94
 * $FreeBSD: src/sys/kern/tty.c,v 1.129.2.5 2002/03/11 01:32:31 dd Exp $
 */

/*
 * MPSAFE NOTE:
 * Almost all functions in this file are acquiring the tty token due to their
 * access and modifications of the 'tp' (struct tty) objects.
 */

/*-
 * TODO:
 *      o Fix races for sending the start char in ttyflush().
 *      o Handle inter-byte timeout for "MIN > 0, TIME > 0" in ttyselect().
 *        With luck, there will be MIN chars before select() returns().
 *      o Handle CLOCAL consistently for ptys.  Perhaps disallow setting it.
 *      o Don't allow input in TS_ZOMBIE case.  It would be visible through
 *        FIONREAD.
 *      o Do the new sio locking stuff here and use it to avoid special
 *        case for EXTPROC?
 *      o Lock PENDIN too?
 *      o Move EXTPROC and/or PENDIN to t_state?
 *      o Wrap most of ttioctl in spltty/splx.
 *      o Implement TIOCNOTTY or remove it from <sys/ioctl.h>.
 *      o Send STOP if IXOFF is toggled off while TS_TBLOCK is set.
 *      o Don't allow certain termios flags to affect disciplines other
 *        than TTYDISC.  Cancel their effects before switch disciplines
 *        and ignore them if they are set while we are in another
 *        discipline.
 *      o Now that historical speed conversions are handled here, don't
 *        do them in drivers.
 *      o Check for TS_CARR_ON being set while everything is closed and not
 *        waiting for carrier.  TS_CARR_ON isn't cleared if nothing is open,
 *        so it would live until the next open even if carrier drops.
 *      o Restore TS_WOPEN since it is useful in pstat.  It must be cleared
 *        only when _all_ openers leave open().
 */

#include "opt_uconsole.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/uio.h>
#include <sys/filio.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <sys/caps.h>
#include <sys/tty.h>
#define TTYDEFCHARS
#include <sys/ttydefaults.h>    /* for ttydefchars, CEOT */
#undef  TTYDEFCHARS
#include <sys/fcntl.h>
#include <sys/conf.h>
#include <sys/dkstat.h>
#include <sys/kernel.h>
#include <sys/vnode.h>
#include <sys/signalvar.h>
#include <sys/signal2.h>
#include <sys/resourcevar.h>
#include <sys/filedesc.h>
#include <sys/sysctl.h>
#include <sys/thread2.h>

#include <vm/vm.h>
#include <sys/lock.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_extern.h>

MALLOC_DEFINE(M_TTYS, "ttys", "tty data structures");

static int      proc_compare (struct proc *p1, struct proc *p2);
static int      ttnread (struct tty *tp);
static void     ttyecho (int c, struct tty *tp);
static int      ttyoutput (int c, struct tty *tp);
static void     ttypend (struct tty *tp);
static void     ttyretype (struct tty *tp);
static void     ttyrub (int c, struct tty *tp);
static void     ttyrubo (struct tty *tp, int cnt);
static void     ttyunblock (struct tty *tp);
static int      ttywflush (struct tty *tp);
static int      filt_ttyread (struct knote *kn, long hint);
static void     filt_ttyrdetach (struct knote *kn);
static int      filt_ttywrite (struct knote *kn, long hint);
static void     filt_ttywdetach (struct knote *kn);

/*
 * Table with character classes and parity. The 8th bit indicates parity,
 * the 7th bit indicates the character is an alphameric or underscore (for
 * ALTWERASE), and the low 6 bits indicate delay type.  If the low 6 bits
 * are 0 then the character needs no special processing on output; classes
 * other than 0 might be translated or (not currently) require delays.
 */
#define E       0x00    /* Even parity. */
#define O       0x80    /* Odd parity. */
#define PARITY(c)       (char_type[c] & O)

#define ALPHA   0x40    /* Alpha or underscore. */
#define ISALPHA(c)      (char_type[(c) & TTY_CHARMASK] & ALPHA)

#define CCLASSMASK      0x3f
#define CCLASS(c)       (char_type[c] & CCLASSMASK)

#define BS      BACKSPACE
#define CC      CONTROL
#define CR      RETURN
#define NA      ORDINARY | ALPHA
#define NL      NEWLINE
#define NO      ORDINARY
#define TB      TAB
#define VT      VTAB

static u_char const char_type[] = {
        E|CC, O|CC, O|CC, E|CC, O|CC, E|CC, E|CC, O|CC, /* nul - bel */
        O|BS, E|TB, E|NL, O|CC, E|VT, O|CR, O|CC, E|CC, /* bs - si */
        O|CC, E|CC, E|CC, O|CC, E|CC, O|CC, O|CC, E|CC, /* dle - etb */
        E|CC, O|CC, O|CC, E|CC, O|CC, E|CC, E|CC, O|CC, /* can - us */
        O|NO, E|NO, E|NO, O|NO, E|NO, O|NO, O|NO, E|NO, /* sp - ' */
        E|NO, O|NO, O|NO, E|NO, O|NO, E|NO, E|NO, O|NO, /* ( - / */
        E|NA, O|NA, O|NA, E|NA, O|NA, E|NA, E|NA, O|NA, /* 0 - 7 */
        O|NA, E|NA, E|NO, O|NO, E|NO, O|NO, O|NO, E|NO, /* 8 - ? */
        O|NO, E|NA, E|NA, O|NA, E|NA, O|NA, O|NA, E|NA, /* @ - G */
        E|NA, O|NA, O|NA, E|NA, O|NA, E|NA, E|NA, O|NA, /* H - O */
        E|NA, O|NA, O|NA, E|NA, O|NA, E|NA, E|NA, O|NA, /* P - W */
        O|NA, E|NA, E|NA, O|NO, E|NO, O|NO, O|NO, O|NA, /* X - _ */
        E|NO, O|NA, O|NA, E|NA, O|NA, E|NA, E|NA, O|NA, /* ` - g */
        O|NA, E|NA, E|NA, O|NA, E|NA, O|NA, O|NA, E|NA, /* h - o */
        O|NA, E|NA, E|NA, O|NA, E|NA, O|NA, O|NA, E|NA, /* p - w */
        E|NA, O|NA, O|NA, E|NO, O|NO, E|NO, E|NO, O|CC, /* x - del */
        /*
         * Meta chars; should be settable per character set;
         * for now, treat them all as normal characters.
         */
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
        NA,   NA,   NA,   NA,   NA,   NA,   NA,   NA,
};
#undef  BS
#undef  CC
#undef  CR
#undef  NA
#undef  NL
#undef  NO
#undef  TB
#undef  VT

/* Macros to clear/set/test flags. */
#define SET(t, f)       (t) |= (f)
#define CLR(t, f)       (t) &= ~(f)
#define ISSET(t, f)     ((t) & (f))

#undef MAX_INPUT                /* XXX wrong in <sys/syslimits.h> */
#define MAX_INPUT       TTYHOG  /* XXX limit is usually larger for !ICANON */

uint64_t tk_nin;
SYSCTL_OPAQUE(_kern, OID_AUTO, tk_nin, CTLFLAG_RD, &tk_nin, sizeof(tk_nin),
    "LU", "TTY input statistic");
uint64_t tk_nout;
SYSCTL_OPAQUE(_kern, OID_AUTO, tk_nout, CTLFLAG_RD, &tk_nout, sizeof(tk_nout),
    "LU", "TTY output statistic");
uint64_t tk_rawcc;

/*
 * list of struct tty where pstat(8) can pick it up with sysctl
 */
static TAILQ_HEAD(, tty) tty_list = TAILQ_HEAD_INITIALIZER(tty_list);

/*
 * Initial open of tty, or (re)entry to standard tty line discipline.
 */
int
ttyopen(cdev_t device, struct tty *tp)
{
        lwkt_gettoken(&tp->t_token);
        tp->t_dev = device;
        if (!ISSET(tp->t_state, TS_ISOPEN)) {
                SET(tp->t_state, TS_ISOPEN);
                if (ISSET(tp->t_cflag, CLOCAL)) {
                        SET(tp->t_state, TS_CONNECTED);
                }
                bzero(&tp->t_winsize, sizeof(tp->t_winsize));
        }
        ttsetwater(tp);
        lwkt_reltoken(&tp->t_token);

        return (0);
}

/*
 * Handle close() on a tty line: flush and set to initial state,
 * bumping generation number so that pending read/write calls
 * can detect recycling of the tty.
 *
 * XXX our caller should have done `spltty(); l_close(); ttyclose();'
 * and l_close() should have flushed, but we repeat the spltty() and
 * the flush in case there are buggy callers.
 */
int
ttyclose(struct tty *tp)
{
        lwkt_gettoken(&tp->t_token);
        funsetown(&tp->t_sigio);
        if (constty == tp)
                constty = NULL;

        ttyflush(tp, FREAD | FWRITE);
        clist_free_cblocks(&tp->t_canq);
        clist_free_cblocks(&tp->t_outq);
        clist_free_cblocks(&tp->t_rawq);

        tp->t_gen++;
        tp->t_line = TTYDISC;
        ttyclearsession(tp);
        tp->t_state &= TS_REGISTERED;   /* clear all bits except */
        lwkt_reltoken(&tp->t_token);

        return (0);
}

/*
 * Disassociate the tty from its session.  Traditionally this has only been
 * a half-close, meaning that the session was still allowed to point at the
 * tty (resulting in the tty in the ps command showing something like 'p0-'),
 * even though the tty is no longer pointing at the session.
 *
 * The half close seems to be useful only for 'ps' output but there is as
 * yet no reason to remove the feature.  The full-close code is currently
 * #if 0'd out.  See also sess_rele() in kern/kern_proc.c.
 */
void
ttyclearsession(struct tty *tp)
{
        struct session *sp;
        struct procglob *prg;
        struct pgrp *opgrp;

        lwkt_gettoken(&tp->t_token);
        opgrp = tp->t_pgrp;
        tp->t_pgrp = NULL;
        if (opgrp) {
                pgrel(opgrp);
                opgrp = NULL;
        }

again:
        if ((sp = tp->t_session) != NULL) {
                prg = sp->s_prg;
                lwkt_gettoken(&prg->proc_token);
                if (sp != tp->t_session) {
                        lwkt_reltoken(&prg->proc_token);
                        goto again;
                }
                tp->t_session = NULL;

#ifdef TTY_DO_FULL_CLOSE
                /* FULL CLOSE (not yet) */
                if (sp->s_ttyp == tp) {
                        sp->s_ttyp = NULL;
                        ttyunhold(tp);
                } else {
                        kprintf("ttyclearsession: warning: sp->s_ttyp != tp "
                                "%p/%p\n", sp->s_ttyp, tp);
                }
#endif
                lwkt_reltoken(&prg->proc_token);
        }
        lwkt_reltoken(&tp->t_token);
}

/*
 * Release the tty vnode association for a session.  This is the 
 * 'other half' of the close.  Because multiple opens of /dev/tty
 * only generate a single open to the actual tty, the file modes
 * are locked to FREAD|FWRITE.
 *
 * If dorevoke is non-zero, the session is also revoked.  We have to
 * close the vnode if VCTTYISOPEN is set.
 */
void
ttyclosesession(struct session *sp, int dorevoke)
{
        struct vnode *vp;
        struct procglob *prg;

        prg = sp->s_prg;
        lwkt_gettoken(&prg->proc_token);
retry:
        /*
         * There may not be a controlling terminal or it may have been closed
         * out from under us.
         */
        if ((vp = sp->s_ttyvp) == NULL) {
                lwkt_reltoken(&prg->proc_token);
                return;
        }

        /*
         * We need a lock if we have to close or revoke.
         */
        if ((vp->v_flag & VCTTYISOPEN) || dorevoke) {
                vhold(vp);
                if (vn_lock(vp, LK_EXCLUSIVE | LK_RETRY | LK_FAILRECLAIM)) {
                        vdrop(vp);
                        goto retry;
                }

                /*
                 * Retry if the vnode was ripped out from under us
                 */
                if (vp != sp->s_ttyvp) {
                        vn_unlock(vp);
                        vdrop(vp);
                        goto retry;
                }

                /*
                 * Close and revoke as needed
                 */
                sp->s_ttyvp = NULL;
                if (vp->v_flag & VCTTYISOPEN) {
                        vclrflags(vp, VCTTYISOPEN);
                        VOP_CLOSE(vp, FREAD|FWRITE, NULL);
                }
                vn_unlock(vp);
                if (dorevoke)
                        vrevoke(vp, proc0.p_ucred);
                vdrop(vp);
        } else {
                sp->s_ttyvp = NULL;
        }
        vrele(vp);
        lwkt_reltoken(&prg->proc_token);
}

#define FLUSHQ(q) {                                                     \
        if ((q)->c_cc)                                                  \
                ndflush(q, (q)->c_cc);                                  \
}

/* Is 'c' a line delimiter ("break" character)? */
#define TTBREAKC(c, lflag)                                                      \
        ((c) == '\n' || (((c) == cc[VEOF] ||                            \
          (c) == cc[VEOL] || ((c) == cc[VEOL2] && lflag & IEXTEN)) &&   \
         (c) != _POSIX_VDISABLE))

/*
 * Process input of a single character received on a tty.
 */
int
ttyinput(int c, struct tty *tp)
{
        tcflag_t iflag, lflag;
        cc_t *cc;
        int i, err;

        lwkt_gettoken(&tp->t_token);
        /*
         * If input is pending take it first.
         */
        lflag = tp->t_lflag;
        if (ISSET(lflag, PENDIN))
                ttypend(tp);
        /*
         * Gather stats.
         */
        if (ISSET(lflag, ICANON))
                ++tp->t_cancc;
        else
                ++tp->t_rawcc;
        ++tk_nin;

        /*
         * Block further input iff:
         * current input > threshold AND input is available to user program
         * AND input flow control is enabled and not yet invoked.
         * The 3 is slop for PARMRK.
         */
        iflag = tp->t_iflag;
        if (tp->t_rawq.c_cc + tp->t_canq.c_cc > tp->t_ihiwat - 3 &&
            (!ISSET(lflag, ICANON) || tp->t_canq.c_cc != 0) &&
            (ISSET(tp->t_cflag, CRTS_IFLOW) || ISSET(iflag, IXOFF)) &&
            !ISSET(tp->t_state, TS_TBLOCK))
                ttyblock(tp);

        /* Handle exceptional conditions (break, parity, framing). */
        cc = tp->t_cc;
        err = (ISSET(c, TTY_ERRORMASK));
        if (err) {
                CLR(c, TTY_ERRORMASK);
                if (ISSET(err, TTY_BI)) {
                        if (ISSET(iflag, IGNBRK)) {
                                lwkt_reltoken(&tp->t_token);
                                return (0);
                        }
                        if (ISSET(iflag, BRKINT)) {
                                ttyflush(tp, FREAD | FWRITE);
                                pgsignal(tp->t_pgrp, SIGINT, 1);
                                goto endcase;
                        }
                        if (ISSET(iflag, PARMRK))
                                goto parmrk;
                } else if ((ISSET(err, TTY_PE) && ISSET(iflag, INPCK))
                        || ISSET(err, TTY_FE)) {
                        if (ISSET(iflag, IGNPAR)) {
                                lwkt_reltoken(&tp->t_token);
                                return (0);
                        }
                        else if (ISSET(iflag, PARMRK)) {
parmrk:
                                if (tp->t_rawq.c_cc + tp->t_canq.c_cc >
                                    MAX_INPUT - 3)
                                        goto input_overflow;
                                clist_putc(0377 | TTY_QUOTE, &tp->t_rawq);
                                clist_putc(0 | TTY_QUOTE, &tp->t_rawq);
                                clist_putc(c | TTY_QUOTE, &tp->t_rawq);
                                goto endcase;
                        } else
                                c = 0;
                }
        }

        if (!ISSET(tp->t_state, TS_TYPEN) && ISSET(iflag, ISTRIP))
                CLR(c, 0x80);
        if (!ISSET(lflag, EXTPROC)) {
                /*
                 * Check for literal nexting very first
                 */
                if (ISSET(tp->t_state, TS_LNCH)) {
                        SET(c, TTY_QUOTE);
                        CLR(tp->t_state, TS_LNCH);
                }
                /*
                 * Scan for special characters.  This code
                 * is really just a big case statement with
                 * non-constant cases.  The bottom of the
                 * case statement is labeled ``endcase'', so goto
                 * it after a case match, or similar.
                 */

                /*
                 * Control chars which aren't controlled
                 * by ICANON, ISIG, or IXON.
                 */
                if (ISSET(lflag, IEXTEN)) {
                        if (CCEQ(cc[VLNEXT], c)) {
                                if (ISSET(lflag, ECHO)) {
                                        if (ISSET(lflag, ECHOE)) {
                                                (void)ttyoutput('^', tp);
                                                (void)ttyoutput('\b', tp);
                                        } else
                                                ttyecho(c, tp);
                                }
                                SET(tp->t_state, TS_LNCH);
                                goto endcase;
                        }
                        if (CCEQ(cc[VDISCARD], c)) {
                                if (ISSET(lflag, FLUSHO))
                                        CLR(tp->t_lflag, FLUSHO);
                                else {
                                        ttyflush(tp, FWRITE);
                                        ttyecho(c, tp);
                                        if (tp->t_rawq.c_cc + tp->t_canq.c_cc)
                                                ttyretype(tp);
                                        SET(tp->t_lflag, FLUSHO);
                                }
                                goto startoutput;
                        }
                }
                /*
                 * Signals.
                 */
                if (ISSET(lflag, ISIG)) {
                        if (CCEQ(cc[VINTR], c) || CCEQ(cc[VQUIT], c)) {
                                if (!ISSET(lflag, NOFLSH))
                                        ttyflush(tp, FREAD | FWRITE);
                                ttyecho(c, tp);
                                pgsignal(tp->t_pgrp,
                                    CCEQ(cc[VINTR], c) ? SIGINT : SIGQUIT, 1);
                                goto endcase;
                        }
                        if (CCEQ(cc[VSUSP], c)) {
                                if (!ISSET(lflag, NOFLSH))
                                        ttyflush(tp, FREAD);
                                ttyecho(c, tp);
                                pgsignal(tp->t_pgrp, SIGTSTP, 1);
                                goto endcase;
                        }
                }
                /*
                 * Handle start/stop characters.
                 */
                if (ISSET(iflag, IXON)) {
                        if (CCEQ(cc[VSTOP], c)) {
                                if (!ISSET(tp->t_state, TS_TTSTOP)) {
                                        SET(tp->t_state, TS_TTSTOP);
                                        (*tp->t_stop)(tp, 0);
                                        lwkt_reltoken(&tp->t_token);
                                        return (0);
                                }
                                if (!CCEQ(cc[VSTART], c)) {
                                        lwkt_reltoken(&tp->t_token);
                                        return (0);
                                }
                                /*
                                 * if VSTART == VSTOP then toggle
                                 */
                                goto endcase;
                        }
                        if (CCEQ(cc[VSTART], c))
                                goto restartoutput;
                }
                /*
                 * IGNCR, ICRNL, & INLCR
                 */
                if (c == '\r') {
                        if (ISSET(iflag, IGNCR)) {
                                lwkt_reltoken(&tp->t_token);
                                return (0);
                        }
                        else if (ISSET(iflag, ICRNL))
                                c = '\n';
                } else if (c == '\n' && ISSET(iflag, INLCR))
                        c = '\r';
        }
        if (!ISSET(tp->t_lflag, EXTPROC) && ISSET(lflag, ICANON)) {
                /*
                 * From here on down canonical mode character
                 * processing takes place.
                 */
                /*
                 * erase or erase2 (^H / ^?)
                 */
                if (CCEQ(cc[VERASE], c) || CCEQ(cc[VERASE2], c) ) {
                        if (tp->t_rawq.c_cc)
                                ttyrub(clist_unputc(&tp->t_rawq), tp);
                        goto endcase;
                }
                /*
                 * kill (^U)
                 */
                if (CCEQ(cc[VKILL], c)) {
                        if (ISSET(lflag, ECHOKE) &&
                            tp->t_rawq.c_cc == tp->t_rocount &&
                            !ISSET(lflag, ECHOPRT))
                                while (tp->t_rawq.c_cc)
                                        ttyrub(clist_unputc(&tp->t_rawq), tp);
                        else {
                                ttyecho(c, tp);
                                if (ISSET(lflag, ECHOK) ||
                                    ISSET(lflag, ECHOKE))
                                        ttyecho('\n', tp);
                                FLUSHQ(&tp->t_rawq);
                                tp->t_rocount = 0;
                        }
                        CLR(tp->t_state, TS_LOCAL);
                        goto endcase;
                }
                /*
                 * word erase (^W)
                 */
                if (CCEQ(cc[VWERASE], c) && ISSET(lflag, IEXTEN)) {
                        int ctype;

                        /*
                         * erase whitespace
                         */
                        while ((c = clist_unputc(&tp->t_rawq)) == ' ' || c == '\t')
                                ttyrub(c, tp);
                        if (c == -1)
                                goto endcase;
                        /*
                         * erase last char of word and remember the
                         * next chars type (for ALTWERASE)
                         */
                        ttyrub(c, tp);
                        c = clist_unputc(&tp->t_rawq);
                        if (c == -1)
                                goto endcase;
                        if (c == ' ' || c == '\t') {
                                clist_putc(c, &tp->t_rawq);
                                goto endcase;
                        }
                        ctype = ISALPHA(c);
                        /*
                         * erase rest of word
                         */
                        do {
                                ttyrub(c, tp);
                                c = clist_unputc(&tp->t_rawq);
                                if (c == -1)
                                        goto endcase;
                        } while (c != ' ' && c != '\t' &&
                            (!ISSET(lflag, ALTWERASE) || ISALPHA(c) == ctype));
                        clist_putc(c, &tp->t_rawq);
                        goto endcase;
                }
                /*
                 * reprint line (^R)
                 */
                if (CCEQ(cc[VREPRINT], c) && ISSET(lflag, IEXTEN)) {
                        ttyretype(tp);
                        goto endcase;
                }
                /*
                 * ^T - kernel info and generate SIGINFO
                 */
                if (CCEQ(cc[VSTATUS], c) && ISSET(lflag, IEXTEN)) {
                        if (ISSET(lflag, ISIG))
                                pgsignal(tp->t_pgrp, SIGINFO, 1);
                        if (!ISSET(lflag, NOKERNINFO))
                                ttyinfo(tp);
                        goto endcase;
                }
                if (CCEQ(cc[VCHECKPT], c) && ISSET(lflag, IEXTEN)) {
                        if (ISSET(lflag, ISIG))
                                pgsignal(tp->t_pgrp, SIGCKPT, 1);
                        goto endcase;
                }
        }
        /*
         * Check for input buffer overflow
         */
        if (tp->t_rawq.c_cc + tp->t_canq.c_cc >= MAX_INPUT) {
input_overflow:
                if (ISSET(iflag, IMAXBEL)) {
                        if (tp->t_outq.c_cc < tp->t_ohiwat)
                                (void)ttyoutput(CTRL('g'), tp);
                }
                goto endcase;
        }

        if (c == 0377 && ISSET(iflag, PARMRK) && !ISSET(iflag, ISTRIP) &&
            ISSET(iflag, IGNBRK|IGNPAR) != (IGNBRK|IGNPAR)) {
                clist_putc(0377 | TTY_QUOTE, &tp->t_rawq);
        }

        /*
         * Put data char in q for user and
         * wakeup on seeing a line delimiter.
         */
        if (clist_putc(c, &tp->t_rawq) >= 0) {
                if (!ISSET(lflag, ICANON)) {
                        ttwakeup(tp);
                        ttyecho(c, tp);
                        goto endcase;
                }
                if (TTBREAKC(c, lflag)) {
                        tp->t_rocount = 0;
                        clist_catq(&tp->t_rawq, &tp->t_canq);
                        ttwakeup(tp);
                } else if (tp->t_rocount++ == 0)
                        tp->t_rocol = tp->t_column;
                if (ISSET(tp->t_state, TS_ERASE)) {
                        /*
                         * end of prterase \.../
                         */
                        CLR(tp->t_state, TS_ERASE);
                        (void)ttyoutput('/', tp);
                }
                i = tp->t_column;
                ttyecho(c, tp);
                if (CCEQ(cc[VEOF], c) && ISSET(lflag, ECHO)) {
                        /*
                         * Place the cursor over the '^' of the ^D.
                         */
                        i = imin(2, tp->t_column - i);
                        while (i > 0) {
                                (void)ttyoutput('\b', tp);
                                i--;
                        }
                }
        }
endcase:
        /*
         * IXANY means allow any character to restart output.
         */
        if (ISSET(tp->t_state, TS_TTSTOP) &&
            !ISSET(iflag, IXANY) && cc[VSTART] != cc[VSTOP]) {
                lwkt_reltoken(&tp->t_token);
                return (0);
        }
restartoutput:
        CLR(tp->t_lflag, FLUSHO);
        CLR(tp->t_state, TS_TTSTOP);
startoutput:
        lwkt_reltoken(&tp->t_token);
        return (ttstart(tp));
}

/*
 * Output a single character on a tty, doing output processing
 * as needed (expanding tabs, newline processing, etc.).
 * Returns < 0 if succeeds, otherwise returns char to resend.
 * Must be recursive.
 */
static int
ttyoutput(int c, struct tty *tp)
{
        tcflag_t oflag;
        int col;

        lwkt_gettoken(&tp->t_token);
        oflag = tp->t_oflag;
        if (!ISSET(oflag, OPOST)) {
                if (ISSET(tp->t_lflag, FLUSHO)) {
                        lwkt_reltoken(&tp->t_token);
                        return (-1);
                }
                if (clist_putc(c, &tp->t_outq)) {
                        lwkt_reltoken(&tp->t_token);
                        return (c);
                }
                tk_nout++;
                tp->t_outcc++;
                lwkt_reltoken(&tp->t_token);
                return (-1);
        }
        /*
         * Do tab expansion if OXTABS aka TAB3 is set.  Special case if we
         * external processing, we don't do the tab expansion because we'll
         * probably get it wrong.  If tab expansion needs to be done, let
         * it happen externally.
         */
        CLR(c, ~TTY_CHARMASK);
        if (c == '\t' &&
            ISSET(oflag, OXTABS) && !ISSET(tp->t_lflag, EXTPROC)) {
                c = 8 - (tp->t_column & 7);
                if (!ISSET(tp->t_lflag, FLUSHO)) {
                        c -= clist_btoq("        ", c, &tp->t_outq);
                        tk_nout += c;
                        tp->t_outcc += c;
                }
                tp->t_column += c;
                lwkt_reltoken(&tp->t_token);
                return (c ? -1 : '\t');
        }
        if (c == CEOT && ISSET(oflag, ONOEOT)) {
                lwkt_reltoken(&tp->t_token);
                return (-1);
        }

        /*
         * Newline translation: if ONLCR is set,
         * translate newline into "\r\n".
         */
        if (c == '\n' && ISSET(tp->t_oflag, ONLCR)) {
                tk_nout++;
                tp->t_outcc++;
                if (!ISSET(tp->t_lflag, FLUSHO) && clist_putc('\r', &tp->t_outq)) {
                        lwkt_reltoken(&tp->t_token);
                        return (c);
                }
        }
        /* If OCRNL is set, translate "\r" into "\n". */
        else if (c == '\r' && ISSET(tp->t_oflag, OCRNL))
                c = '\n';
        /* If ONOCR is set, don't transmit CRs when on column 0. */
        else if (c == '\r' && ISSET(tp->t_oflag, ONOCR) && tp->t_column == 0) {
                lwkt_reltoken(&tp->t_token);
                return (-1);
        }

        tk_nout++;
        tp->t_outcc++;
        if (!ISSET(tp->t_lflag, FLUSHO) && clist_putc(c, &tp->t_outq)) {
                lwkt_reltoken(&tp->t_token);
                return (c);
        }

        col = tp->t_column;
        switch (CCLASS(c)) {
        case BACKSPACE:
                if (col > 0)
                        --col;
                break;
        case CONTROL:
                break;
        case NEWLINE:
                if (ISSET(tp->t_oflag, ONLCR | ONLRET))
                        col = 0;
                break;
        case RETURN:
                col = 0;
                break;
        case ORDINARY:
                ++col;
                break;
        case TAB:
                col = (col + 8) & ~7;
                break;
        }
        tp->t_column = col;
        lwkt_reltoken(&tp->t_token);

        return (-1);
}

/*
 * Ioctls for all tty devices.  Called after line-discipline specific ioctl
 * has been called to do discipline-specific functions and/or reject any
 * of these ioctl commands.
 */
/* ARGSUSED */
int
ttioctl(struct tty *tp, u_long cmd, void *data, int flag)
{
        struct thread *td = curthread;
        struct lwp *lp = td->td_lwp;
        struct proc *p = td->td_proc;
        struct pgrp *opgrp;
        struct tty *otp;
        int error;

        KKASSERT(p);
        lwkt_gettoken(&tp->t_token);
        lwkt_gettoken(&p->p_token);

        /* If the ioctl involves modification, hang if in the background. */
        switch (cmd) {
        case  TIOCCBRK:
        case  TIOCCONS:
        case  TIOCDRAIN:
        case  TIOCEXCL:
        case  TIOCFLUSH:
#ifdef TIOCHPCL
        case  TIOCHPCL:
#endif
        case  TIOCNXCL:
        case  TIOCSBRK:
        case  TIOCSCTTY:
        case  TIOCSDRAINWAIT:
        case  TIOCSETA:
        case  TIOCSETAF:
        case  TIOCSETAW:
        case  TIOCSETD:
        case  TIOCSPGRP:
        case  TIOCSTART:
        case  TIOCSTAT:
        case  TIOCSTI:
        case  TIOCSTOP:
        case  TIOCSWINSZ:
                while (isbackground(p, tp) && !(p->p_flags & P_PPWAIT) &&
                    !SIGISMEMBER(p->p_sigignore, SIGTTOU) &&
                    !SIGISMEMBER(lp->lwp_sigmask, SIGTTOU)) {
                        if (p->p_pgrp->pg_jobc == 0) {
                                lwkt_reltoken(&p->p_token);
                                lwkt_reltoken(&tp->t_token);
                                return (EIO);
                        }
                        pgsignal(p->p_pgrp, SIGTTOU, 1);
                        error = ttysleep(tp, &lbolt, PCATCH, "ttybg1",
                                         0);
                        if (error) {
                                lwkt_reltoken(&p->p_token);
                                lwkt_reltoken(&tp->t_token);
                                return (error);
                        }
                }
                break;
        }

        switch (cmd) {                  /* Process the ioctl. */
        case FIOASYNC:                  /* set/clear async i/o */
                if (*(int *)data)
                        SET(tp->t_state, TS_ASYNC);
                else
                        CLR(tp->t_state, TS_ASYNC);
                break;
        case FIONREAD:                  /* get # bytes to read */
                *(int *)data = ttnread(tp);
                break;

        case FIOSETOWN:
                /*
                 * Policy -- Don't allow FIOSETOWN on someone else's 
                 *           controlling tty
                 */
                if (tp->t_session != NULL && !isctty(p, tp)) {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (ENOTTY);
                }

                error = fsetown(*(int *)data, &tp->t_sigio);
                if (error) {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (error);
                }
                break;
        case FIOGETOWN:
                if (tp->t_session != NULL && !isctty(p, tp)) {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (ENOTTY);
                }
                *(int *)data = fgetown(&tp->t_sigio);
                break;

        case TIOCEXCL:                  /* set exclusive use of tty */
                SET(tp->t_state, TS_XCLUDE);
                break;
        case TIOCFLUSH: {               /* flush buffers */
                int flags = *(int *)data;

                if (flags == 0)
                        flags = FREAD | FWRITE;
                else
                        flags &= FREAD | FWRITE;
                ttyflush(tp, flags);
                break;
        }
        case TIOCCONS:                  /* become virtual console */
                if (*(int *)data) {
                        if (constty && constty != tp &&
                            ISSET(constty->t_state, TS_CONNECTED)) {
                                lwkt_reltoken(&p->p_token);
                                lwkt_reltoken(&tp->t_token);
                                return (EBUSY);
                        }
#ifndef UCONSOLE
                        error = caps_priv_check_td(td, SYSCAP_RESTRICTEDROOT);
                        if (error) {
                                lwkt_reltoken(&p->p_token);
                                lwkt_reltoken(&tp->t_token);
                                return (error);
                        }
#endif
                        constty = tp;
                } else if (tp == constty)
                        constty = NULL;
                break;
        case TIOCDRAIN:                 /* wait till output drained */
                error = ttywait(tp);
                if (error) {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (error);
                }
                break;
        case TIOCGETA: {                /* get termios struct */
                struct termios *t = (struct termios *)data;

                bcopy(&tp->t_termios, t, sizeof(struct termios));
                break;
        }
        case TIOCGETD:                  /* get line discipline */
                *(int *)data = tp->t_line;
                break;
        case TIOCGWINSZ:                /* get window size */
                *(struct winsize *)data = tp->t_winsize;
                break;
        case TIOCGPGRP:                 /* get pgrp of tty */
                if (!isctty(p, tp)) {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (ENOTTY);
                }
                *(int *)data = tp->t_pgrp ? tp->t_pgrp->pg_id : NO_PID;
                break;
        case TIOCGSID:                  /* get sid of tty */
                if (!isctty(p, tp)) {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (ENOTTY);
                }
                *(int *)data = tp->t_session->s_sid;
                break;
#ifdef TIOCHPCL
        case TIOCHPCL:                  /* hang up on last close */
                SET(tp->t_cflag, HUPCL);
                break;
#endif
        case TIOCNXCL:                  /* reset exclusive use of tty */
                CLR(tp->t_state, TS_XCLUDE);
                break;
        case TIOCOUTQ:                  /* output queue size */
                *(int *)data = tp->t_outq.c_cc;
                break;
        case TIOCSETA:                  /* set termios struct */
        case TIOCSETAW:                 /* drain output, set */
        case TIOCSETAF: {               /* drn out, fls in, set */
                struct termios *t = (struct termios *)data;

                if (t->c_ispeed == 0)
                        t->c_ispeed = t->c_ospeed;
                if (t->c_ispeed == 0)
                        t->c_ispeed = tp->t_ospeed;
                if (t->c_ispeed == 0) {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (EINVAL);
                }
                if (cmd == TIOCSETAW || cmd == TIOCSETAF) {
                        error = ttywait(tp);
                        if (error) {
                                lwkt_reltoken(&p->p_token);
                                lwkt_reltoken(&tp->t_token);
                                return (error);
                        }
                        if (cmd == TIOCSETAF)
                                ttyflush(tp, FREAD);
                }
                if (!ISSET(t->c_cflag, CIGNORE)) {
                        /*
                         * Set device hardware.
                         */
                        if (tp->t_param && (error = (*tp->t_param)(tp, t))) {
                                lwkt_reltoken(&p->p_token);
                                lwkt_reltoken(&tp->t_token);
                                return (error);
                        }
                        if (ISSET(t->c_cflag, CLOCAL) &&
                            !ISSET(tp->t_cflag, CLOCAL)) {
                                /*
                                 * XXX disconnections would be too hard to
                                 * get rid of without this kludge.  The only
                                 * way to get rid of controlling terminals
                                 * is to exit from the session leader.
                                 */
                                CLR(tp->t_state, TS_ZOMBIE);

                                wakeup(TSA_CARR_ON(tp));
                                ttwakeup(tp);
                                ttwwakeup(tp);
                        }
                        if ((ISSET(tp->t_state, TS_CARR_ON) ||
                             ISSET(t->c_cflag, CLOCAL)) &&
                            !ISSET(tp->t_state, TS_ZOMBIE))
                                SET(tp->t_state, TS_CONNECTED);
                        else
                                CLR(tp->t_state, TS_CONNECTED);
                        tp->t_cflag = t->c_cflag;
                        tp->t_ispeed = t->c_ispeed;
                        if (t->c_ospeed != 0)
                                tp->t_ospeed = t->c_ospeed;
                        ttsetwater(tp);
                }
                if (ISSET(t->c_lflag, ICANON) != ISSET(tp->t_lflag, ICANON) &&
                    cmd != TIOCSETAF) {
                        if (ISSET(t->c_lflag, ICANON))
                                SET(tp->t_lflag, PENDIN);
                        else {
                                /*
                                 * XXX we really shouldn't allow toggling
                                 * ICANON while we're in a non-termios line
                                 * discipline.  Now we have to worry about
                                 * panicing for a null queue.
                                 */
                                if (tp->t_canq.c_ccmax > 0 &&
                                    tp->t_rawq.c_ccmax > 0) {
                                        clist_catq(&tp->t_rawq, &tp->t_canq);
                                        /*
                                         * XXX the queue limits may be
                                         * different, so the old queue
                                         * swapping method no longer works.
                                         */
                                        clist_catq(&tp->t_canq, &tp->t_rawq);
                                }
                                CLR(tp->t_lflag, PENDIN);
                        }
                        ttwakeup(tp);
                }
                tp->t_iflag = t->c_iflag;
                tp->t_oflag = t->c_oflag;
                /*
                 * Make the EXTPROC bit read only.
                 */
                if (ISSET(tp->t_lflag, EXTPROC))
                        SET(t->c_lflag, EXTPROC);
                else
                        CLR(t->c_lflag, EXTPROC);
                tp->t_lflag = t->c_lflag | ISSET(tp->t_lflag, PENDIN);
                if (t->c_cc[VMIN] != tp->t_cc[VMIN] ||
                    t->c_cc[VTIME] != tp->t_cc[VTIME])
                        ttwakeup(tp);
                bcopy(t->c_cc, tp->t_cc, sizeof(t->c_cc));
                break;
        }
        case TIOCSETD: {                /* set line discipline */
                int t = *(int *)data;
                cdev_t device = tp->t_dev;

                if ((u_int)t >= nlinesw) {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (ENXIO);
                }
                if (t != tp->t_line) {
                        (*linesw[tp->t_line].l_close)(tp, flag);
                        error = (*linesw[t].l_open)(device, tp);
                        if (error) {
                                (void)(*linesw[tp->t_line].l_open)(device, tp);
                                lwkt_reltoken(&p->p_token);
                                lwkt_reltoken(&tp->t_token);
                                return (error);
                        }
                        tp->t_line = t;
                }
                break;
        }
        case TIOCSTART:                 /* start output, like ^Q */
                if (ISSET(tp->t_state, TS_TTSTOP) ||
                    ISSET(tp->t_lflag, FLUSHO)) {
                        CLR(tp->t_lflag, FLUSHO);
                        CLR(tp->t_state, TS_TTSTOP);
                        ttstart(tp);
                }
                break;
        case TIOCSTI:                   /* simulate terminal input */
                if ((flag & FREAD) == 0 &&
                    caps_priv_check_td(td, SYSCAP_RESTRICTEDROOT))
                {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (EPERM);
                }
                if (!isctty(p, tp) &&
                    caps_priv_check_td(td, SYSCAP_RESTRICTEDROOT))
                {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (EACCES);
                }
                (*linesw[tp->t_line].l_rint)(*(u_char *)data, tp);
                break;
        case TIOCSTOP:                  /* stop output, like ^S */
                if (!ISSET(tp->t_state, TS_TTSTOP)) {
                        SET(tp->t_state, TS_TTSTOP);
                        (*tp->t_stop)(tp, 0);
                }
                break;
        case TIOCSCTTY:                 /* become controlling tty */
                /* Session ctty vnode pointer set in vnode layer. */
                if (!SESS_LEADER(p) ||
                    ((p->p_session->s_ttyvp || tp->t_session) &&
                    (tp->t_session != p->p_session))) {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (EPERM);
                }
                ttyhold(tp);
                tp->t_session = p->p_session;
                opgrp = tp->t_pgrp;
                pgref(p->p_pgrp);
                tp->t_pgrp = p->p_pgrp;
                otp = p->p_session->s_ttyp;
                p->p_session->s_ttyp = tp;
                p->p_flags |= P_CONTROLT;
                if (otp)
                        ttyunhold(otp);
                if (opgrp) {
                        pgrel(opgrp);
                        opgrp = NULL;
                }
                break;
        case TIOCSPGRP: {               /* set pgrp of tty */
                pid_t pgid = *(int *)data;

                if (!isctty(p, tp)) {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (ENOTTY);
                }
                else if (pgid < 1 || pgid > PID_MAX) {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (EINVAL);
                } else {
                        struct pgrp *pgrp = pgfind(pgid);
                        if (pgrp == NULL || pgrp->pg_session != p->p_session) {
                                if (pgrp)
                                        pgrel(pgrp);
                                lwkt_reltoken(&p->p_token);
                                lwkt_reltoken(&tp->t_token);
                                return (EPERM);
                        }
                        opgrp = tp->t_pgrp;
                        tp->t_pgrp = pgrp;
                        if (opgrp) {
                                pgrel(opgrp);
                                opgrp = NULL;
                        }
                }
                break;
        }
        case TIOCSTAT:                  /* simulate control-T */
                ttyinfo(tp);
                break;
        case TIOCSWINSZ:                /* set window size */
                if (bcmp((caddr_t)&tp->t_winsize, data,
                    sizeof (struct winsize))) {
                        tp->t_winsize = *(struct winsize *)data;
                        pgsignal(tp->t_pgrp, SIGWINCH, 1);
                }
                break;
        case TIOCSDRAINWAIT:
                error = caps_priv_check_td(td, SYSCAP_RESTRICTEDROOT);
                if (error) {
                        lwkt_reltoken(&p->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (error);
                }
                tp->t_timeout = *(int *)data * hz;
                wakeup(TSA_OCOMPLETE(tp));
                wakeup(TSA_OLOWAT(tp));
                break;
        case TIOCGDRAINWAIT:
                *(int *)data = tp->t_timeout / hz;
                break;
        default:
                lwkt_reltoken(&p->p_token);
                lwkt_reltoken(&tp->t_token);
                return (ENOIOCTL);
        }
        lwkt_reltoken(&p->p_token);
        lwkt_reltoken(&tp->t_token);
        return (0);
}

static struct filterops ttyread_filtops =
        { FILTEROP_ISFD|FILTEROP_MPSAFE, NULL, filt_ttyrdetach, filt_ttyread };
static struct filterops ttywrite_filtops =
        { FILTEROP_ISFD|FILTEROP_MPSAFE, NULL, filt_ttywdetach, filt_ttywrite };

int
ttykqfilter(struct dev_kqfilter_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct knote *kn = ap->a_kn;
        struct tty *tp = dev->si_tty;
        struct klist *klist;

        ap->a_result = 0;

        lwkt_gettoken(&tp->t_token);
        switch (kn->kn_filter) {
        case EVFILT_READ:
                klist = &tp->t_rkq.ki_note;
                kn->kn_fop = &ttyread_filtops;
                break;
        case EVFILT_WRITE:
                klist = &tp->t_wkq.ki_note;
                kn->kn_fop = &ttywrite_filtops;
                break;
        default:
                ap->a_result = EOPNOTSUPP;
                lwkt_reltoken(&tp->t_token);
                return (0);
        }
        lwkt_reltoken(&tp->t_token);
        kn->kn_hook = (caddr_t)dev;
        knote_insert(klist, kn);

        return (0);
}

static void
filt_ttyrdetach(struct knote *kn)
{
        struct tty *tp = ((cdev_t)kn->kn_hook)->si_tty;

        lwkt_gettoken(&tp->t_token);
        knote_remove(&tp->t_rkq.ki_note, kn);
        lwkt_reltoken(&tp->t_token);
}

static int
filt_ttyread(struct knote *kn, long hint)
{
        struct tty *tp = ((cdev_t)kn->kn_hook)->si_tty;

        lwkt_gettoken(&tp->t_token);
        kn->kn_data = ttnread(tp);
        if (ISSET(tp->t_state, TS_ZOMBIE)) {
                kn->kn_flags |= (EV_EOF | EV_NODATA);
                lwkt_reltoken(&tp->t_token);
                return (1);
        }
        lwkt_reltoken(&tp->t_token);
        return (kn->kn_data > 0);
}

static void
filt_ttywdetach(struct knote *kn)
{
        struct tty *tp = ((cdev_t)kn->kn_hook)->si_tty;

        lwkt_gettoken(&tp->t_token);
        knote_remove(&tp->t_wkq.ki_note, kn);
        lwkt_reltoken(&tp->t_token);
}

static int
filt_ttywrite(struct knote *kn, long hint)
{
        struct tty *tp = ((cdev_t)kn->kn_hook)->si_tty;
        int ret;

        lwkt_gettoken(&tp->t_token);
        kn->kn_data = tp->t_outq.c_cc;
        if (ISSET(tp->t_state, TS_ZOMBIE)) {
                lwkt_reltoken(&tp->t_token);
                return (1);
        }
        ret = (kn->kn_data <= tp->t_olowat &&
            ISSET(tp->t_state, TS_CONNECTED));
        lwkt_reltoken(&tp->t_token);
        return ret;
}

/*
 * NOTE: tp->t_token must be held.
 */
static int
ttnread(struct tty *tp)
{
        int nread;

        ASSERT_LWKT_TOKEN_HELD(&tp->t_token);
        if (ISSET(tp->t_lflag, PENDIN))
                ttypend(tp);
        nread = tp->t_canq.c_cc;
        if (!ISSET(tp->t_lflag, ICANON)) {
                nread += tp->t_rawq.c_cc;
                if (nread < tp->t_cc[VMIN] && tp->t_cc[VTIME] == 0)
                        nread = 0;
        }
        return (nread);
}

/*
 * Wait for output to drain.
 */
int
ttywait(struct tty *tp)
{
        int error;

        error = 0;
        lwkt_gettoken(&tp->t_token);
        while ((tp->t_outq.c_cc || ISSET(tp->t_state, TS_BUSY)) &&
               ISSET(tp->t_state, TS_CONNECTED) && tp->t_oproc) {
                (*tp->t_oproc)(tp);
                if ((tp->t_outq.c_cc || ISSET(tp->t_state, TS_BUSY)) &&
                    ISSET(tp->t_state, TS_CONNECTED)) {
                        SET(tp->t_state, TS_SO_OCOMPLETE);
                        error = ttysleep(tp, TSA_OCOMPLETE(tp),
                                         PCATCH, "ttywai",
                                         tp->t_timeout);
                        if (error) {
                                if (error == EWOULDBLOCK)
                                        error = EIO;
                                break;
                        }
                } else
                        break;
        }
        if (!error && (tp->t_outq.c_cc || ISSET(tp->t_state, TS_BUSY)))
                error = EIO;
        lwkt_reltoken(&tp->t_token);

        return (error);
}

/*
 * Flush if successfully wait.
 */
static int
ttywflush(struct tty *tp)
{
        int error;

        if ((error = ttywait(tp)) == 0)
                ttyflush(tp, FREAD);
        return (error);
}

/*
 * Flush tty read and/or write queues, notifying anyone waiting.
 */
void
ttyflush(struct tty *tp, int rw)
{
        lwkt_gettoken(&tp->t_token);
#if 0
again:
#endif
        if (rw & FWRITE) {
                FLUSHQ(&tp->t_outq);
                CLR(tp->t_state, TS_TTSTOP);
        }
        (*tp->t_stop)(tp, rw);
        if (rw & FREAD) {
                FLUSHQ(&tp->t_canq);
                FLUSHQ(&tp->t_rawq);
                CLR(tp->t_lflag, PENDIN);
                tp->t_rocount = 0;
                tp->t_rocol = 0;
                CLR(tp->t_state, TS_LOCAL);
                ttwakeup(tp);
                if (ISSET(tp->t_state, TS_TBLOCK)) {
                        if (rw & FWRITE)
                                FLUSHQ(&tp->t_outq);
                        ttyunblock(tp);

                        /*
                         * Don't let leave any state that might clobber the
                         * next line discipline (although we should do more
                         * to send the START char).  Not clearing the state
                         * may have caused the "putc to a clist with no
                         * reserved cblocks" panic/kprintf.
                         */
                        CLR(tp->t_state, TS_TBLOCK);

#if 0 /* forget it, sleeping isn't always safe and we don't know when it is */
                        if (ISSET(tp->t_iflag, IXOFF)) {
                                /*
                                 * XXX wait a bit in the hope that the stop
                                 * character (if any) will go out.  Waiting
                                 * isn't good since it allows races.  This
                                 * will be fixed when the stop character is
                                 * put in a special queue.  Don't bother with
                                 * the checks in ttywait() since the timeout
                                 * will save us.
                                 */
                                SET(tp->t_state, TS_SO_OCOMPLETE);
                                ttysleep(tp, TSA_OCOMPLETE(tp), 0,
                                         "ttyfls", hz / 10);
                                /*
                                 * Don't try sending the stop character again.
                                 */
                                CLR(tp->t_state, TS_TBLOCK);
                                goto again;
                        }
#endif
                }
        }
        if (rw & FWRITE) {
                FLUSHQ(&tp->t_outq);
                ttwwakeup(tp);
        }
        lwkt_reltoken(&tp->t_token);
}

/*
 * Copy in the default termios characters.
 */
void
termioschars(struct termios *t)
{
        bcopy(ttydefchars, t->c_cc, sizeof t->c_cc);
}

/*
 * Old interface.
 */
void
ttychars(struct tty *tp)
{
        lwkt_gettoken(&tp->t_token);
        termioschars(&tp->t_termios);
        lwkt_reltoken(&tp->t_token);
}

/*
 * Handle input high water.  Send stop character for the IXOFF case.  Turn
 * on our input flow control bit and propagate the changes to the driver.
 * XXX the stop character should be put in a special high priority queue.
 */
void
ttyblock(struct tty *tp)
{
        lwkt_gettoken(&tp->t_token);
        SET(tp->t_state, TS_TBLOCK);
        if (ISSET(tp->t_iflag, IXOFF) && tp->t_cc[VSTOP] != _POSIX_VDISABLE &&
            clist_putc(tp->t_cc[VSTOP], &tp->t_outq) != 0)
                CLR(tp->t_state, TS_TBLOCK);    /* try again later */
        ttstart(tp);
        lwkt_reltoken(&tp->t_token);
}

/*
 * Handle input low water.  Send start character for the IXOFF case.  Turn
 * off our input flow control bit and propagate the changes to the driver.
 * XXX the start character should be put in a special high priority queue.
 */
static void
ttyunblock(struct tty *tp)
{
        lwkt_gettoken(&tp->t_token);
        CLR(tp->t_state, TS_TBLOCK);
        if (ISSET(tp->t_iflag, IXOFF) && tp->t_cc[VSTART] != _POSIX_VDISABLE &&
            clist_putc(tp->t_cc[VSTART], &tp->t_outq) != 0)
                SET(tp->t_state, TS_TBLOCK);    /* try again later */
        ttstart(tp);
        lwkt_reltoken(&tp->t_token);
}

int
ttstart(struct tty *tp)
{
        lwkt_gettoken(&tp->t_token);
        if (tp->t_oproc != NULL)        /* XXX: Kludge for pty. */
                (*tp->t_oproc)(tp);
        lwkt_reltoken(&tp->t_token);
        return (0);
}

/*
 * "close" a line discipline
 */
int
ttylclose(struct tty *tp, int flag)
{
        lwkt_gettoken(&tp->t_token);
        if (flag & FNONBLOCK || ttywflush(tp))
                ttyflush(tp, FREAD | FWRITE);
        lwkt_reltoken(&tp->t_token);
        return (0);
}

void
ttyhold(struct tty *tp)
{
        lwkt_gettoken(&tp->t_token);
        ++tp->t_refs;
        lwkt_reltoken(&tp->t_token);
}

void
ttyunhold(struct tty *tp)
{
        lwkt_gettoken(&tp->t_token);
        if (tp->t_unhold)
                tp->t_unhold(tp);
        else
                --tp->t_refs;
        lwkt_reltoken(&tp->t_token);
}

/*
 * Handle modem control transition on a tty.
 * Flag indicates new state of carrier.
 * Returns 0 if the line should be turned off, otherwise 1.
 */
int
ttymodem(struct tty *tp, int flag)
{
        lwkt_gettoken(&tp->t_token);
        if (ISSET(tp->t_state, TS_CARR_ON) && ISSET(tp->t_cflag, MDMBUF)) {
                /*
                 * MDMBUF: do flow control according to carrier flag
                 * XXX TS_CAR_OFLOW doesn't do anything yet.  TS_TTSTOP
                 * works if IXON and IXANY are clear.
                 */
                if (flag) {
                        CLR(tp->t_state, TS_CAR_OFLOW);
                        CLR(tp->t_state, TS_TTSTOP);
                        ttstart(tp);
                } else if (!ISSET(tp->t_state, TS_CAR_OFLOW)) {
                        SET(tp->t_state, TS_CAR_OFLOW);
                        SET(tp->t_state, TS_TTSTOP);
                        (*tp->t_stop)(tp, 0);
                }
        } else if (flag == 0) {
                /*
                 * Lost carrier.
                 */
                CLR(tp->t_state, TS_CARR_ON);
                if (ISSET(tp->t_state, TS_ISOPEN) &&
                    !ISSET(tp->t_cflag, CLOCAL)) {
                        SET(tp->t_state, TS_ZOMBIE);
                        CLR(tp->t_state, TS_CONNECTED);
                        if (tp->t_session && tp->t_session->s_leader)
                                ksignal(tp->t_session->s_leader, SIGHUP);
                        ttyflush(tp, FREAD | FWRITE);
                        lwkt_reltoken(&tp->t_token);
                        return (0);
                }
        } else {
                /*
                 * Carrier now on.
                 */
                SET(tp->t_state, TS_CARR_ON);
                if (!ISSET(tp->t_state, TS_ZOMBIE))
                        SET(tp->t_state, TS_CONNECTED);
                wakeup(TSA_CARR_ON(tp));
                ttwakeup(tp);
                ttwwakeup(tp);
        }
        lwkt_reltoken(&tp->t_token);
        return (1);
}

/*
 * Reinput pending characters after state switch
 */
static void
ttypend(struct tty *tp)
{
        struct clist tq;
        int c;

        lwkt_gettoken(&tp->t_token);
        CLR(tp->t_lflag, PENDIN);
        SET(tp->t_state, TS_TYPEN);
        /*
         * XXX this assumes too much about clist internals.  It may even
         * fail if the cblock slush pool is empty.  We can't allocate more
         * cblocks here because we are called from an interrupt handler
         * and clist_alloc_cblocks() can wait.
         */
        tq = tp->t_rawq;
        bzero(&tp->t_rawq, sizeof tp->t_rawq);
        clist_alloc_cblocks(&tp->t_rawq, tq.c_ccmax);
        while ((c = clist_getc(&tq)) >= 0)
                ttyinput(c, tp);
        CLR(tp->t_state, TS_TYPEN);
        clist_free_cblocks(&tq);
        lwkt_reltoken(&tp->t_token);
}

/*
 * Process a read call on a tty device.
 */
int
ttread(struct tty *tp, struct uio *uio, int flag)
{
        struct clist *qp;
        int c;
        tcflag_t lflag;
        cc_t *cc = tp->t_cc;
        struct proc *pp;
        struct lwp *lp;
        int first, error = 0;
        int has_stime = 0, last_cc = 0;
        long slp = 0;           /* XXX this should be renamed `timo'. */
        struct timeval stime;

        lp = curthread->td_lwp;
        stime.tv_sec = 0;       /* fix compiler warnings */
        stime.tv_usec = 0;

        lwkt_gettoken(&tp->t_token);
loop:
        lflag = tp->t_lflag;
        /*
         * take pending input first
         */
        if (ISSET(lflag, PENDIN)) {
                ttypend(tp);
                splz();         /* reduce latency */
                lflag = tp->t_lflag;    /* XXX ttypend() clobbers it */
        }

        /*
         * Hang process if it's in the background.
         */
        if ((pp = curproc) != NULL)
                lwkt_gettoken(&pp->p_token);
        if (pp && isbackground(pp, tp)) {
                if (SIGISMEMBER(pp->p_sigignore, SIGTTIN) ||
                    SIGISMEMBER(lp->lwp_sigmask, SIGTTIN) ||
                    (pp->p_flags & P_PPWAIT) || pp->p_pgrp->pg_jobc == 0) {
                        lwkt_reltoken(&pp->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (EIO);
                }
                pgsignal(pp->p_pgrp, SIGTTIN, 1);
                error = ttysleep(tp, &lbolt, PCATCH, "ttybg2", 0);
                if (error) {
                        lwkt_reltoken(&pp->p_token);
                        lwkt_reltoken(&tp->t_token);
                        return (error);
                }
                lwkt_reltoken(&pp->p_token);
                goto loop;
        }
        if (pp)
                lwkt_reltoken(&pp->p_token);

        if (ISSET(tp->t_state, TS_ZOMBIE)) {
                lwkt_reltoken(&tp->t_token);
                return (0);     /* EOF */
        }

        /*
         * If canonical, use the canonical queue,
         * else use the raw queue.
         *
         * (should get rid of clists...)
         */
        qp = ISSET(lflag, ICANON) ? &tp->t_canq : &tp->t_rawq;

        if (flag & IO_NDELAY) {
                if (qp->c_cc > 0)
                        goto read;
                if (!ISSET(lflag, ICANON) && cc[VMIN] == 0) {
                        lwkt_reltoken(&tp->t_token);
                        return (0);
                }
                lwkt_reltoken(&tp->t_token);
                return (EWOULDBLOCK);
        }
        if (!ISSET(lflag, ICANON)) {
                int m = cc[VMIN];
                long t = cc[VTIME];
                struct timeval timecopy;

                /*
                 * Check each of the four combinations.
                 * (m > 0 && t == 0) is the normal read case.
                 * It should be fairly efficient, so we check that and its
                 * companion case (m == 0 && t == 0) first.
                 * For the other two cases, we compute the target sleep time
                 * into slp.
                 */
                if (t == 0) {
                        if (qp->c_cc < m)
                                goto sleep;
                        if (qp->c_cc > 0)
                                goto read;

                        /* m, t and qp->c_cc are all 0.  0 is enough input. */
                        lwkt_reltoken(&tp->t_token);
                        return (0);
                }
                t *= 100000;            /* time in us */
#define diff(t1, t2) (((t1).tv_sec - (t2).tv_sec) * 1000000 + \
                         ((t1).tv_usec - (t2).tv_usec))
                if (m > 0) {
                        if (qp->c_cc <= 0)
                                goto sleep;
                        if (qp->c_cc >= m)
                                goto read;
                        getmicrotime(&timecopy);
                        if (has_stime == 0) {
                                /* first character, start timer */
                                has_stime = 1;
                                stime = timecopy;
                                slp = t;
                        } else if (qp->c_cc > last_cc) {
                                /* got a character, restart timer */
                                stime = timecopy;
                                slp = t;
                        } else {
                                /* nothing, check expiration */
                                slp = t - diff(timecopy, stime);
                                if (slp <= 0)
                                        goto read;
                        }
                        last_cc = qp->c_cc;
                } else {        /* m == 0 */
                        if (qp->c_cc > 0)
                                goto read;
                        getmicrotime(&timecopy);
                        if (has_stime == 0) {
                                has_stime = 1;
                                stime = timecopy;
                                slp = t;
                        } else {
                                slp = t - diff(timecopy, stime);
                                if (slp <= 0) {
                                        /* Timed out, but 0 is enough input. */
                                        lwkt_reltoken(&tp->t_token);
                                        return (0);
                                }
                        }
                }
#undef diff
                /*
                 * Rounding down may make us wake up just short
                 * of the target, so we round up.
                 * The formula is ceiling(slp * hz/1000000).
                 * 32-bit arithmetic is enough for hz < 169.
                 * XXX see tvtohz() for how to avoid overflow if hz
                 * is large (divide by `tick' and/or arrange to
                 * use tvtohz() if hz is large).
                 */
                slp = (long) (((u_long)slp * hz) + 999999) / 1000000;
                goto sleep;
        }
        if (qp->c_cc <= 0) {
sleep:
                /*
                 * There is no input, or not enough input and we can block.
                 */
                error = ttysleep(tp, TSA_HUP_OR_INPUT(tp), PCATCH,
                                 ISSET(tp->t_state, TS_CONNECTED) ?
                                 "ttyin" : "ttyhup", (int)slp);
                if (error == EWOULDBLOCK)
                        error = 0;
                else if (error) {
                        lwkt_reltoken(&tp->t_token);
                        return (error);
                }
                /*
                 * XXX what happens if another process eats some input
                 * while we are asleep (not just here)?  It would be
                 * safest to detect changes and reset our state variables
                 * (has_stime and last_cc).
                 */
                slp = 0;
                goto loop;
        }
read:
        /*
         * Input present, check for input mapping and processing.
         */
        first = 1;
        if (ISSET(lflag, ICANON | ISIG))
                goto slowcase;
        for (;;) {
                char ibuf[IBUFSIZ];
                int icc;

                icc = (int)szmin(uio->uio_resid, IBUFSIZ);
                icc = clist_qtob(qp, ibuf, icc);
                if (icc <= 0) {
                        if (first)
                                goto loop;
                        break;
                }
                error = uiomove(ibuf, (size_t)icc, uio);
                /*
                 * XXX if there was an error then we should ungetc() the
                 * unmoved chars and reduce icc here.
                 */
                if (error)
                        break;
                if (uio->uio_resid == 0)
                        break;
                first = 0;
        }
        goto out;
slowcase:
        for (;;) {
                c = clist_getc(qp);
                if (c < 0) {
                        if (first)
                                goto loop;
                        break;
                }
                /*
                 * delayed suspend (^Y)
                 */
                if (CCEQ(cc[VDSUSP], c) &&
                    ISSET(lflag, IEXTEN | ISIG) == (IEXTEN | ISIG)) {
                        pgsignal(tp->t_pgrp, SIGTSTP, 1);
                        if (first) {
                                error = ttysleep(tp, &lbolt, PCATCH,
                                                 "ttybg3", 0);
                                if (error)
                                        break;
                                goto loop;
                        }
                        break;
                }
                /*
                 * Interpret EOF only in canonical mode.
                 */
                if (CCEQ(cc[VEOF], c) && ISSET(lflag, ICANON))
                        break;
                /*
                 * Give user character.
                 */
                error = ureadc(c, uio);
                if (error)
                        /* XXX should ungetc(c, qp). */
                        break;
                if (uio->uio_resid == 0)
                        break;
                /*
                 * In canonical mode check for a "break character"
                 * marking the end of a "line of input".
                 */
                if (ISSET(lflag, ICANON) && TTBREAKC(c, lflag))
                        break;
                first = 0;
        }

out:
        /*
         * Look to unblock input now that (presumably)
         * the input queue has gone down.
         */
        if (ISSET(tp->t_state, TS_TBLOCK) &&
            tp->t_rawq.c_cc + tp->t_canq.c_cc <= tp->t_ilowat) {
                ttyunblock(tp);
        }

        lwkt_reltoken(&tp->t_token);
        return (error);
}

/*
 * Check the output queue on tp for space for a kernel message (from uprintf
 * or tprintf).  Allow some space over the normal hiwater mark so we don't
 * lose messages due to normal flow control, but don't let the tty run amok.
 * Sleeps here are not interruptible, but we return prematurely if new signals
 * arrive.
 */
int
ttycheckoutq(struct tty *tp, int wait)
{
        struct lwp *lp = curthread->td_lwp;
        int hiwat;
        sigset_t oldset, newset;

        lwkt_gettoken(&tp->t_token);
        hiwat = tp->t_ohiwat;
        SIGEMPTYSET(oldset);
        SIGEMPTYSET(newset);
        if (wait)
                oldset = lwp_sigpend(lp);
        if (tp->t_outq.c_cc > hiwat + OBUFSIZ + 100) {
                while (tp->t_outq.c_cc > hiwat) {
                        ttstart(tp);
                        if (tp->t_outq.c_cc <= hiwat)
                                break;
                        if (wait)
                                newset = lwp_sigpend(lp);
                        if (!wait || SIGSETNEQ(oldset, newset)) {
                                lwkt_reltoken(&tp->t_token);
                                return (0);
                        }
                        SET(tp->t_state, TS_SO_OLOWAT);
                        tsleep(TSA_OLOWAT(tp), 0, "ttoutq", hz);
                }
        }
        lwkt_reltoken(&tp->t_token);
        return (1);
}

/*
 * Process a write call on a tty device.
 */
int
ttwrite(struct tty *tp, struct uio *uio, int flag)
{
        char *cp = NULL;
        int cc, ce;
        struct proc *pp;
        struct lwp *lp;
        int i, hiwat, error;
        size_t cnt;

        char obuf[OBUFSIZ];

        lwkt_gettoken(&tp->t_token);
        lp = curthread->td_lwp;
        hiwat = tp->t_ohiwat;
        cnt = uio->uio_resid;
        error = 0;
        cc = 0;
loop:
        if (ISSET(tp->t_state, TS_ZOMBIE)) {
                if (uio->uio_resid == cnt)
                        error = EIO;
                goto out;
        }
        if (!ISSET(tp->t_state, TS_CONNECTED)) {
                if (flag & IO_NDELAY) {
                        error = EWOULDBLOCK;
                        goto out;
                }
                error = ttysleep(tp, TSA_CARR_ON(tp), PCATCH, "ttydcd", 0);
                if (error)
                        goto out;
                goto loop;
        }

        /*
         * Hang the process if it's in the background.
         */
        if ((pp = curproc) != NULL)
                lwkt_gettoken(&pp->p_token);
        if (pp && isbackground(pp, tp) &&
            ISSET(tp->t_lflag, TOSTOP) && !(pp->p_flags & P_PPWAIT) &&
            !SIGISMEMBER(pp->p_sigignore, SIGTTOU) &&
            !SIGISMEMBER(lp->lwp_sigmask, SIGTTOU)) {
                if (pp->p_pgrp->pg_jobc == 0) {
                        error = EIO;
                        lwkt_reltoken(&pp->p_token);
                        goto out;
                }
                pgsignal(pp->p_pgrp, SIGTTOU, 1);
                lwkt_reltoken(&pp->p_token);
                error = ttysleep(tp, &lbolt, PCATCH, "ttybg4", 0);
                if (error)
                        goto out;
                goto loop;
        }
        if (pp)
                lwkt_reltoken(&pp->p_token);
        /*
         * Process the user's data in at most OBUFSIZ chunks.  Perform any
         * output translation.  Keep track of high water mark, sleep on
         * overflow awaiting device aid in acquiring new space.
         */
        while (uio->uio_resid > 0 || cc > 0) {
                if (ISSET(tp->t_lflag, FLUSHO)) {
                        uio->uio_resid = 0;
                        lwkt_reltoken(&tp->t_token);
                        return (0);
                }
                if (tp->t_outq.c_cc > hiwat)
                        goto ovhiwat;
                /*
                 * Grab a hunk of data from the user, unless we have some
                 * leftover from last time.
                 */
                if (cc == 0) {
                        cc = szmin(uio->uio_resid, OBUFSIZ);
                        cp = obuf;
                        error = uiomove(cp, (size_t)cc, uio);
                        if (error) {
                                cc = 0;
                                break;
                        }
                }
                /*
                 * If nothing fancy need be done, grab those characters we
                 * can handle without any of ttyoutput's processing and
                 * just transfer them to the output q.  For those chars
                 * which require special processing (as indicated by the
                 * bits in char_type), call ttyoutput.  After processing
                 * a hunk of data, look for FLUSHO so ^O's will take effect
                 * immediately.
                 */
                while (cc > 0) {
                        if (!ISSET(tp->t_oflag, OPOST))
                                ce = cc;
                        else {
                                ce = cc - scanc((u_int)cc, (u_char *)cp,
                                                char_type, CCLASSMASK);
                                /*
                                 * If ce is zero, then we're processing
                                 * a special character through ttyoutput.
                                 */
                                if (ce == 0) {
                                        tp->t_rocount = 0;
                                        if (ttyoutput(*cp, tp) >= 0) {
                                                /* No Clists, wait a bit. */
                                                ttstart(tp);
                                                if (flag & IO_NDELAY) {
                                                        error = EWOULDBLOCK;
                                                        goto out;
                                                }
                                                error = ttysleep(tp, &lbolt,
                                                                 PCATCH,
                                                                 "ttybf1", 0);
                                                if (error)
                                                        goto out;
                                                goto loop;
                                        }
                                        cp++;
                                        cc--;
                                        if (ISSET(tp->t_lflag, FLUSHO) ||
                                            tp->t_outq.c_cc > hiwat)
                                                goto ovhiwat;
                                        continue;
                                }
                        }
                        /*
                         * A bunch of normal characters have been found.
                         * Transfer them en masse to the output queue and
                         * continue processing at the top of the loop.
                         * If there are any further characters in this
                         * <= OBUFSIZ chunk, the first should be a character
                         * requiring special handling by ttyoutput.
                         */
                        tp->t_rocount = 0;
                        i = clist_btoq(cp, ce, &tp->t_outq);
                        ce -= i;
                        tp->t_column += ce;
                        cp += ce, cc -= ce, tk_nout += ce;
                        tp->t_outcc += ce;
                        if (i > 0) {
                                /* No Clists, wait a bit. */
                                ttstart(tp);
                                if (flag & IO_NDELAY) {
                                        error = EWOULDBLOCK;
                                        goto out;
                                }
                                error = ttysleep(tp, &lbolt, PCATCH,
                                                 "ttybf2", 0);
                                if (error)
                                        goto out;
                                goto loop;
                        }
                        if (ISSET(tp->t_lflag, FLUSHO) ||
                            tp->t_outq.c_cc > hiwat)
                                break;
                }
                ttstart(tp);
        }
out:
        /*
         * If cc is nonzero, we leave the uio structure inconsistent, as the
         * offset and iov pointers have moved forward, but it doesn't matter
         * (the call will either return short or restart with a new uio).
         */
        uio->uio_resid += cc;
        lwkt_reltoken(&tp->t_token);
        return (error);

ovhiwat:
        ttstart(tp);
        /*
         * This can only occur if FLUSHO is set in t_lflag,
         * or if ttstart/oproc is synchronous (or very fast).
         */
        if (tp->t_outq.c_cc <= hiwat) {
                goto loop;
        }
        if (flag & IO_NDELAY) {
                uio->uio_resid += cc;
                lwkt_reltoken(&tp->t_token);
                return (uio->uio_resid == cnt ? EWOULDBLOCK : 0);
        }
        SET(tp->t_state, TS_SO_OLOWAT);
        error = ttysleep(tp, TSA_OLOWAT(tp), PCATCH, "ttywri", tp->t_timeout);
        if (error == EWOULDBLOCK)
                error = EIO;
        if (error)
                goto out;
        goto loop;
}

/*
 * Rubout one character from the rawq of tp
 * as cleanly as possible.
 * NOTE: Must be called with tp->t_token held
 */
static void
ttyrub(int c, struct tty *tp)
{
        void *cp;
        int savecol;
        int tabc;

        ASSERT_LWKT_TOKEN_HELD(&tp->t_token);
        if (!ISSET(tp->t_lflag, ECHO) || ISSET(tp->t_lflag, EXTPROC))
                return;
        CLR(tp->t_lflag, FLUSHO);
        if (ISSET(tp->t_lflag, ECHOE)) {
                if (tp->t_rocount == 0) {
                        /*
                         * Screwed by ttwrite; retype
                         */
                        ttyretype(tp);
                        return;
                }
                if (c == ('\t' | TTY_QUOTE) || c == ('\n' | TTY_QUOTE))
                        ttyrubo(tp, 2);
                else {
                        CLR(c, ~TTY_CHARMASK);
                        switch (CCLASS(c)) {
                        case ORDINARY:
                                ttyrubo(tp, 1);
                                break;
                        case BACKSPACE:
                        case CONTROL:
                        case NEWLINE:
                        case RETURN:
                        case VTAB:
                                if (ISSET(tp->t_lflag, ECHOCTL))
                                        ttyrubo(tp, 2);
                                break;
                        case TAB:
                                if (tp->t_rocount < tp->t_rawq.c_cc) {
                                        ttyretype(tp);
                                        return;
                                }
                                savecol = tp->t_column;
                                SET(tp->t_state, TS_CNTTB);
                                SET(tp->t_lflag, FLUSHO);
                                tp->t_column = tp->t_rocol;

                                cp = clist_nextc(&tp->t_rawq, NULL, &tabc);
                                while (cp) {
                                        ttyecho(tabc, tp);
                                        cp = clist_nextc(&tp->t_rawq,
                                                         cp, &tabc);
                                }
                                CLR(tp->t_lflag, FLUSHO);
                                CLR(tp->t_state, TS_CNTTB);

                                /* savecol will now be length of the tab. */
                                savecol -= tp->t_column;
                                tp->t_column += savecol;
                                if (savecol > 8)
                                        savecol = 8;    /* overflow screw */
                                while (--savecol >= 0)
                                        (void)ttyoutput('\b', tp);
                                break;
                        default:                        /* XXX */
#define PANICSTR        "ttyrub: would panic c = %d, val = %d\n"
                                (void)kprintf(PANICSTR, c, CCLASS(c));
#ifdef notdef
                                panic(PANICSTR, c, CCLASS(c));
#endif
                        }
                }
        } else if (ISSET(tp->t_lflag, ECHOPRT)) {
                if (!ISSET(tp->t_state, TS_ERASE)) {
                        SET(tp->t_state, TS_ERASE);
                        (void)ttyoutput('\\', tp);
                }
                ttyecho(c, tp);
        } else {
                ttyecho(tp->t_cc[VERASE], tp);
                /*
                 * This code may be executed not only when an ERASE key
                 * is pressed, but also when ^U (KILL) or ^W (WERASE) are.
                 * So, I didn't think it was worthwhile to pass the extra
                 * information (which would need an extra parameter,
                 * changing every call) needed to distinguish the ERASE2
                 * case from the ERASE.
                 */
        }
        --tp->t_rocount;
}

/*
 * Back over cnt characters, erasing them.
 * NOTE: Must be called with tp->t_token held
 */
static void
ttyrubo(struct tty *tp, int cnt)
{
        ASSERT_LWKT_TOKEN_HELD(&tp->t_token);
        while (cnt-- > 0) {
                (void)ttyoutput('\b', tp);
                (void)ttyoutput(' ', tp);
                (void)ttyoutput('\b', tp);
        }
}

/*
 * ttyretype --
 *      Reprint the rawq line.  Note, it is assumed that c_cc has already
 *      been checked.
 * NOTE: Must be called with tp->t_token held
 */
static void
ttyretype(struct tty *tp)
{
        void *cp;
        int c;

        ASSERT_LWKT_TOKEN_HELD(&tp->t_token);
        /* Echo the reprint character. */
        if (tp->t_cc[VREPRINT] != _POSIX_VDISABLE)
                ttyecho(tp->t_cc[VREPRINT], tp);

        (void)ttyoutput('\n', tp);

        /*
         * XXX
         * FIX: NEXTC IS BROKEN - DOESN'T CHECK QUOTE
         * BIT OF FIRST CHAR.
         */
        cp = clist_nextc(&tp->t_canq, NULL, &c);
        while (cp) {
                ttyecho(c, tp);
                cp = clist_nextc(&tp->t_canq, cp, &c);
        }
        cp = clist_nextc(&tp->t_rawq, NULL, &c);
        while (cp) {
                ttyecho(c, tp);
                cp = clist_nextc(&tp->t_rawq, cp, &c);
        }
        CLR(tp->t_state, TS_ERASE);

        tp->t_rocount = tp->t_rawq.c_cc;
        tp->t_rocol = 0;
}

/*
 * Echo a typed character to the terminal.
 * NOTE: Must be called with tp->t_token held
 */
static void
ttyecho(int c, struct tty *tp)
{
        ASSERT_LWKT_TOKEN_HELD(&tp->t_token);

        if (!ISSET(tp->t_state, TS_CNTTB))
                CLR(tp->t_lflag, FLUSHO);
        if ((!ISSET(tp->t_lflag, ECHO) &&
             (c != '\n' || !ISSET(tp->t_lflag, ECHONL))) ||
            ISSET(tp->t_lflag, EXTPROC))
                return;
        if (ISSET(tp->t_lflag, ECHOCTL) &&
            ((ISSET(c, TTY_CHARMASK) <= 037 && c != '\t' && c != '\n') ||
            ISSET(c, TTY_CHARMASK) == 0177)) {
                (void)ttyoutput('^', tp);
                CLR(c, ~TTY_CHARMASK);
                if (c == 0177)
                        c = '?';
                else
                        c += 'A' - 1;
        }
        (void)ttyoutput(c, tp);
}

/*
 * Wake up any readers on a tty.
 */
void
ttwakeup(struct tty *tp)
{
        lwkt_gettoken(&tp->t_token);
        if (ISSET(tp->t_state, TS_ASYNC) && tp->t_sigio != NULL)
                pgsigio(tp->t_sigio, SIGIO, (tp->t_session != NULL));
        wakeup(TSA_HUP_OR_INPUT(tp));
        KNOTE(&tp->t_rkq.ki_note, 0);
        lwkt_reltoken(&tp->t_token);
}

/*
 * Wake up any writers on a tty.
 */
void
ttwwakeup(struct tty *tp)
{
        lwkt_gettoken(&tp->t_token);
        if (ISSET(tp->t_state, TS_ASYNC) && tp->t_sigio != NULL)
                pgsigio(tp->t_sigio, SIGIO, (tp->t_session != NULL));
        if (ISSET(tp->t_state, TS_BUSY | TS_SO_OCOMPLETE) ==
            TS_SO_OCOMPLETE && tp->t_outq.c_cc == 0) {
                CLR(tp->t_state, TS_SO_OCOMPLETE);
                wakeup(TSA_OCOMPLETE(tp));
        }
        if (ISSET(tp->t_state, TS_SO_OLOWAT) &&
            tp->t_outq.c_cc <= tp->t_olowat) {
                CLR(tp->t_state, TS_SO_OLOWAT);
                wakeup(TSA_OLOWAT(tp));
        }
        KNOTE(&tp->t_wkq.ki_note, 0);
        lwkt_reltoken(&tp->t_token);
}

/*
 * Look up a code for a specified speed in a conversion table;
 * used by drivers to map software speed values to hardware parameters.
 * No requirements
 */
int
ttspeedtab(int speed, struct speedtab *table)
{

        for ( ; table->sp_speed != -1; table++)
                if (table->sp_speed == speed)
                        return (table->sp_code);
        return (-1);
}

/*
 * Set input and output watermarks and buffer sizes.  For input, the
 * high watermark is about one second's worth of input above empty, the
 * low watermark is slightly below high water, and the buffer size is a
 * driver-dependent amount above high water.  For output, the watermarks
 * are near the ends of the buffer, with about 1 second's worth of input
 * between them.  All this only applies to the standard line discipline.
 */
#define CLAMP(x, h, l)  ((x) > h ? h : ((x) < l) ? l : (x))

void
ttsetwater(struct tty *tp)
{
        int ttmaxhiwat;         /* maximum high water mark */
        int cps;                /* characters per second */
        int x;

        lwkt_gettoken(&tp->t_token);

        /*
         * Input side.
         *
         * Calculate nominal low and high water marks, leave a little
         * room to absorb flow control latencies.
         */
        clist_alloc_cblocks(&tp->t_canq, TTYHOG);

        switch (tp->t_ispeedwat) {
        case (speed_t)-1:
                cps = tp->t_ispeed / 10;
                break;
        case 0:
                /*
                 * This case is for old drivers that don't know about
                 * t_ispeedwat.  Arrange for them to get the old buffer
                 * sizes and watermarks.
                 */
                cps = TTYHOG - 2 * 256;
                tp->t_ififosize = 2 * 2048;
                break;
        default:
                cps = tp->t_ispeedwat / 10;
                break;
        }
        tp->t_ihiwat = cps;
        tp->t_ilowat = 7 * cps / 8;
        x = cps + tp->t_ififosize;
        clist_alloc_cblocks(&tp->t_rawq, x);

        /*
         * Output side.
         *
         * Calculate nominal low and high water marks, and make the
         * actual buffer just a tad larger to absorb flow control latencies.
         */
        switch (tp->t_ospeedwat) {
        case (speed_t)-1:
                cps = tp->t_ospeed / 10;
                ttmaxhiwat = 2 * TTMAXHIWAT;
                break;
        case 0:
                cps = tp->t_ospeed / 10;
                ttmaxhiwat = TTMAXHIWAT;
                break;
        default:
                cps = tp->t_ospeedwat / 10;
                ttmaxhiwat = 8 * TTMAXHIWAT;
                break;
        }

        x = CLAMP(cps / 2, TTMAXLOWAT, TTMINLOWAT);
        tp->t_olowat = x;

        x += cps;
        x = CLAMP(x, ttmaxhiwat, TTMINHIWAT);
        tp->t_ohiwat = x;

        x = imax(tp->t_ohiwat, TTMAXHIWAT);
        x += OBUFSIZ + 100;
        clist_alloc_cblocks(&tp->t_outq, x);

        lwkt_reltoken(&tp->t_token);
}

#undef  CLAMP

/*
 * Report on state of foreground process group.
 */
void
ttyinfo(struct tty *tp)
{
        struct pgrp *pgrp;
        struct proc *p, *pick;
        struct lwp *lp;
        struct rusage ru;
        char buf[64];
        const char *str;
        struct vmspace *vm;
        long vmsz;
        int pctcpu;
        int tmp;

        if (ttycheckoutq(tp,0) == 0)
                return;

        lwkt_gettoken(&tp->t_token);

        /*
         * We always print the load average, then figure out what else to
         * print based on the state of the current process group.
         */
        tmp = (averunnable.ldavg[0] * 100 + FSCALE / 2) >> FSHIFT;
        ttyprintf(tp, "load: %d.%02d ", tmp / 100, tmp % 100);

        if (tp->t_session == NULL) {
                ttyprintf(tp, "not a controlling terminal\n");
                goto done2;
        }
        if ((pgrp = tp->t_pgrp) == NULL) {
                ttyprintf(tp, "no foreground process group\n");
                goto done2;
        }

        /*
         * Pick an interesting process.  Note that certain elements,
         * in particular the wmesg.
         *
         * NOTE: lwp_wmesg is lwp_thread->td_wmesg.
         */
        pgref(pgrp);
        lwkt_gettoken(&pgrp->pg_token);

        pick = NULL;
        for (p = LIST_FIRST(&pgrp->pg_members);
             p != NULL;
             p = LIST_NEXT(p, p_pglist)) {
                PHOLD(p);
                if (proc_compare(pick, p)) {
                        if (pick)
                                PRELE(pick);
                        pick = p;
                } else {
                        PRELE(p);
                }
        }
        if (pick == NULL) {
                ttyprintf(tp, "empty foreground process group\n");
                goto done1;
        }

        /*
         * Pick an interesting LWP (XXX)
         *
         * pick is held.
         */
        lp = FIRST_LWP_IN_PROC(pick);
        if (lp == NULL) {
                PRELE(pick);
                ttyprintf(tp, "foreground process without lwp\n");
                goto done1;
        }

        /*
         * Figure out what wait/process-state message, and command
         * buffer to present
         */
        /*
         * XXX lwp This is a horrible mixture.  We need to rework this
         * as soon as lwps have their own runnable status.
         */
        LWPHOLD(lp);
        if (pick->p_flags & P_WEXIT)
                str = "exiting";
        else if (lp->lwp_stat == LSRUN)
                str = "running";
        else if (pick->p_stat == SIDL)
                str = "spawning";
        else if (lp->lwp_wmesg) /* lwp_thread must not be NULL */
                str = lp->lwp_wmesg;
        else
                str = "iowait";

        ksnprintf(buf, sizeof(buf), "cmd: %s %d [%s]",
                  pick->p_comm, pick->p_pid, str);

        /*
         * Calculate cpu usage, percent cpu, and cmsz.  Note that
         * 'pick' becomes invalid the moment we release the token.
         */
        if (lp->lwp_thread)
                calcru_proc(pick, &ru);

        pctcpu = (lp->lwp_pctcpu * 10000 + FSCALE / 2) >> FSHIFT;

        LWPRELE(lp);

        /*
         * NOTE: vmspace should be protected from destruction by the
         *       combination of pg_token and the fact that we are not
         *       flagged as a zombie.
         */
        if (pick->p_stat == SIDL || pick->p_stat == SZOMB) {
                vmsz = 0;
        } else if ((vm = pick->p_vmspace) == NULL) {
                vmsz = 0;
        } else {
                vmspace_hold(vm);
                vmsz = pgtok(vmspace_resident_count(vm));
                vmspace_drop(vm);
        }
        PRELE(pick);

        /*
         * Dump the output
         */
        ttyprintf(tp, " %s ",
                  buf);
        ttyprintf(tp, "%ld.%02ldu ",
                  ru.ru_utime.tv_sec, ru.ru_utime.tv_usec / 10000);
        ttyprintf(tp, "%ld.%02lds ",
                  ru.ru_stime.tv_sec, ru.ru_stime.tv_usec / 10000);
        ttyprintf(tp, "%d%% %ldk\n",
                  pctcpu / 100, vmsz);

done1:
        lwkt_reltoken(&pgrp->pg_token);
        pgrel(pgrp);
done2:
        tp->t_rocount = 0;      /* so pending input will be retyped if BS */
        lwkt_reltoken(&tp->t_token);
}

/*
 * Returns 1 if p2 is "better" than p1
 *
 * The algorithm for picking the "interesting" process is thus:
 *
 *      1) Only foreground processes are eligible - implied.
 *      2) Runnable processes are favored over anything else.  The runner
 *         with the highest cpu utilization is picked (p_cpticks).  Ties are
 *         broken by picking the highest pid.
 *      3) The sleeper with the shortest sleep time is next.  With ties,
 *         we pick out just "short-term" sleepers (LWP_SINTR == 0).
 *      4) Further ties are broken by picking the highest pid.
 *
 * NOTE: must be called with p1 and p2 held.
 */
#define ISRUN(lp)       ((lp)->lwp_stat == LSRUN)
#define TESTAB(a, b)    ((a)<<1 | (b))
#define ONLYA   2
#define ONLYB   1
#define BOTH    3

static int
proc_compare(struct proc *p1, struct proc *p2)
{
        struct lwp *lp1, *lp2;
        int res;

        if (p1 == NULL)
                return (1);
        if (lwkt_trytoken(&p1->p_token) == 0)
                return (1);
        if (lwkt_trytoken(&p2->p_token) == 0) {
                lwkt_reltoken(&p1->p_token);
                return (0);
        }

        /*
         * weed out zombies
         */
        switch (TESTAB(p1->p_stat == SZOMB, p2->p_stat == SZOMB)) {
        case ONLYA:
                res = 1;
                goto done;
        case ONLYB:
                res = 0;
                goto done;
        case BOTH:
                res = (p2->p_pid > p1->p_pid);  /* tie - return highest pid */
                goto done;
        default:
                break;
        }

        /* XXX choose the best lwp? */
        lp1 = FIRST_LWP_IN_PROC(p1);
        lp2 = FIRST_LWP_IN_PROC(p2);

        /*
         * Favor one with LWPs verses one that has none (is exiting).
         */
        if (lp1 == NULL) {
                res = 1;
                goto done;
        }
        if (lp2 == NULL) {
                res = 0;
                goto done;
        }

        /*
         * see if at least one of them is runnable
         */
        switch (TESTAB(ISRUN(lp1), ISRUN(lp2))) {
        case ONLYA:
                res = 0;
                goto done;
        case ONLYB:
                res = 1;
                goto done;
        case BOTH:
                /*
                 * tie - favor one with highest recent cpu utilization
                 */
                if (lp2->lwp_cpticks > lp1->lwp_cpticks)
                        res = 1;
                else if (lp1->lwp_cpticks > lp2->lwp_cpticks)
                        res = 0;
                else
                        res = (p2->p_pid > p1->p_pid); /* tie - ret highest */
                goto done;
        default:
                break;
        }

        /*
         * Pick the one with the smallest sleep time
         */
        if (lp2->lwp_slptime > lp1->lwp_slptime) {
                res = 0;
                goto done;
        }
        if (lp1->lwp_slptime > lp2->lwp_slptime) {
                res = 1;
                goto done;
        }

        /*
         * Favor one sleeping in a non-interruptible sleep
         */
        if ((lp1->lwp_flags & LWP_SINTR) && (lp2->lwp_flags & LWP_SINTR) == 0)
                res = 1;
        else
        if ((lp2->lwp_flags & LWP_SINTR) && (lp1->lwp_flags & LWP_SINTR) == 0)
                res = 0;
        else
                res = (p2->p_pid > p1->p_pid);  /* tie - return highest pid */
        /* fall through */

done:
        lwkt_reltoken(&p2->p_token);
        lwkt_reltoken(&p1->p_token);
        return (res);
}

/*
 * Output char to tty; console putchar style.
 */
int
tputchar(int c, struct tty *tp)
{
        lwkt_gettoken(&tp->t_token);
        if (!ISSET(tp->t_state, TS_CONNECTED)) {
                lwkt_reltoken(&tp->t_token);
                return (-1);
        }
        if (c == '\n')
                (void)ttyoutput('\r', tp);
        (void)ttyoutput(c, tp);
        ttstart(tp);
        lwkt_reltoken(&tp->t_token);

        return (0);
}

/*
 * Sleep on chan, returning ERESTART if tty changed while we napped and
 * returning any errors (e.g. EINTR/EWOULDBLOCK) reported by tsleep.  If
 * the tty is revoked, restarting a pending call will redo validation done
 * at the start of the call.
 */
int
ttysleep(struct tty *tp, void *chan, int slpflags, char *wmesg, int timo)
{
        int error;
        int gen;

        gen = tp->t_gen;
        error = tsleep(chan, slpflags, wmesg, timo);
        if (error)
                return (error);
        return (tp->t_gen == gen ? 0 : ERESTART);
}

/*
 * Revoke a tty.
 *
 * We bump the gen to force any ttysleep()'s to return with ERESTART
 * and flush the tty.  The related fp's should already have been
 * replaced so the tty will close when the last references on the
 * original fp's go away.
 */
int
ttyrevoke(struct dev_revoke_args *ap)
{
        struct tty *tp;

        tp = ap->a_head.a_dev->si_tty;
        lwkt_gettoken(&tp->t_token);
        tp->t_gen++;
        ttyflush(tp, FREAD | FWRITE);
        wakeup(TSA_CARR_ON(tp));
        ttwakeup(tp);
        ttwwakeup(tp);
        lwkt_reltoken(&tp->t_token);

        return (0);
}

/*
 * Allocate a tty struct.  Clists in the struct will be allocated by
 * ttyopen().  The tty itself is protected by tp->t_token.  tty_token
 * is primarily used to interlock the NULL test and for registration.
 *
 * by convention, once allocated, tty structures are never freed.  This
 * saves us from numerous release race scenarios that can occur due to the
 * token being embedded in the tty structure.
 */
struct tty *
ttymalloc(struct tty **tpp)
{
        struct tty *tp;

        if ((tp = *tpp) == NULL) {
                tp = kmalloc(sizeof *tp, M_TTYS, M_WAITOK|M_ZERO);
                lwkt_gettoken(&tty_token);
                if (*tpp == NULL) {     /* recheck after blocking kmalloc */
                        *tpp = tp;
                        ttyinit(tp);
                        ttyregister(tp);
                } else {
                        kfree(tp, M_TTYS);
                }
                lwkt_reltoken(&tty_token);
        }
        return (tp);
}

/*
 * Caller must hold tp->t_token
 */
void
ttyunregister(struct tty *tp)
{
        lwkt_gettoken(&tty_token);
        if (ISSET(tp->t_state, TS_REGISTERED)) {
                CLR(tp->t_state, TS_REGISTERED);
                TAILQ_REMOVE(&tty_list, tp, t_list);
        }
        lwkt_reltoken(&tty_token);
}

void
ttyinit(struct tty *tp)
{
        lwkt_token_init(&tp->t_token, "tp");
}

void
ttyregister(struct tty *tp)
{
        lwkt_gettoken(&tty_token);
        if (!ISSET(tp->t_state, TS_REGISTERED)) {
                SET(tp->t_state, TS_REGISTERED);
                TAILQ_INSERT_HEAD(&tty_list, tp, t_list);
        }
        lwkt_reltoken(&tty_token);
}

static int
sysctl_kern_ttys(SYSCTL_HANDLER_ARGS)
{
        int error;
        struct tty *tp;
        struct tty t;
        struct tty marker;

        bzero(&marker, sizeof(marker));
        marker.t_state = TS_MARKER;
        error = 0;

        lwkt_gettoken(&tty_token);

        TAILQ_INSERT_HEAD(&tty_list, &marker, t_list);
        while ((tp = TAILQ_NEXT(&marker, t_list)) != NULL) {
                TAILQ_REMOVE(&tty_list, &marker, t_list);
                TAILQ_INSERT_AFTER(&tty_list, tp, &marker, t_list);
                if (tp->t_state & TS_MARKER)
                        continue;
                t = *tp;
                if (t.t_dev)
                        t.t_dev = (cdev_t)(uintptr_t)devid_from_dev(t.t_dev);
                error = SYSCTL_OUT(req, (caddr_t)&t, sizeof(t));
                if (error)
                        break;
        }
        TAILQ_REMOVE(&tty_list, &marker, t_list);
        lwkt_reltoken(&tty_token);
        return (error);
}

SYSCTL_PROC(_kern, OID_AUTO, ttys, CTLTYPE_OPAQUE|CTLFLAG_RD,
        0, 0, sysctl_kern_ttys, "S,tty", "All struct ttys");

void
nottystop(struct tty *tp, int rw)
{
        return;
}

int
ttyread(struct dev_read_args *ap)
{
        struct tty *tp;
        int ret;

        tp = ap->a_head.a_dev->si_tty;
        if (tp == NULL)
                return (ENODEV);
        lwkt_gettoken(&tp->t_token);
        ret = ((*linesw[tp->t_line].l_read)(tp, ap->a_uio, ap->a_ioflag));
        lwkt_reltoken(&tp->t_token);

        return ret;
}

int
ttywrite(struct dev_write_args *ap)
{
        struct tty *tp;
        int ret;

        tp = ap->a_head.a_dev->si_tty;
        if (tp == NULL)
                return (ENODEV);
        lwkt_gettoken(&tp->t_token);
        ret = ((*linesw[tp->t_line].l_write)(tp, ap->a_uio, ap->a_ioflag));
        lwkt_reltoken(&tp->t_token);

        return ret;
}