Reference count struct tty.
Add two new functions: ttyref() and ttyrel(). ttymalloc() creates a struct tty with a reference count of one. when ttyrel sees the count go to zero, struct tty is freed. Hold references for open ttys and for ttys which are controlling terminal for sessions. Until drivers start using ttyrel(), this commit will make no difference.
This commit is contained in:
phk
parent
f9d30f0a79
commit
2d1181e619
@ -470,8 +470,10 @@ pgdelete(pgrp)
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SESS_UNLOCK(savesess);
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PGRP_UNLOCK(pgrp);
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if (i == 0) {
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if (savesess->s_ttyp != NULL)
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ttyrel(savesess->s_ttyp);
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mtx_destroy(&savesess->s_mtx);
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FREE(pgrp->pg_session, M_SESSION);
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FREE(savesess, M_SESSION);
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}
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mtx_destroy(&pgrp->pg_mtx);
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FREE(pgrp, M_PGRP);
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114
sys/kern/tty.c
114
sys/kern/tty.c
@ -211,8 +211,13 @@ static u_char const char_type[] = {
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/*
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* list of struct tty where pstat(8) can pick it up with sysctl
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*
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* The lock order is to grab the list mutex before the tty mutex.
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* Together with additions going on the tail of the list, this allows
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* the sysctl to avoid doing retries.
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*/
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static SLIST_HEAD(, tty) tty_list;
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static TAILQ_HEAD(, tty) tty_list = TAILQ_HEAD_INITIALIZER(tty_list);
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static struct mtx tty_list_mutex;
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static int drainwait = 5*60;
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SYSCTL_INT(_kern, OID_AUTO, drainwait, CTLFLAG_RW, &drainwait,
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@ -229,6 +234,7 @@ ttyopen(dev_t device, struct tty *tp)
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s = spltty();
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tp->t_dev = device;
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if (!ISSET(tp->t_state, TS_ISOPEN)) {
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ttyref(tp);
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SET(tp->t_state, TS_ISOPEN);
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if (ISSET(tp->t_cflag, CLOCAL))
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SET(tp->t_state, TS_CONNECTED);
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@ -270,6 +276,7 @@ ttyclose(struct tty *tp)
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tp->t_pgrp = NULL;
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tp->t_session = NULL;
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tp->t_state = 0;
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ttyrel(tp);
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splx(s);
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return (0);
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}
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@ -1065,6 +1072,7 @@ ttioctl(struct tty *tp, u_long cmd, void *data, int flag)
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tp->t_session = p->p_session;
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tp->t_pgrp = p->p_pgrp;
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SESS_LOCK(p->p_session);
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ttyref(tp); /* ttyrel(): kern_proc.c:pgdelete() */
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p->p_session->s_ttyp = tp;
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SESS_UNLOCK(p->p_session);
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PROC_LOCK(p);
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@ -2630,6 +2638,51 @@ ttysleep(struct tty *tp, void *chan, int pri, char *wmesg, int timo)
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return (tp->t_gen == gen ? 0 : ERESTART);
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}
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/*
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* Gain a reference to a TTY
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*/
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int
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ttyref(struct tty *tp)
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{
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int i;
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mtx_lock(&tp->t_mtx);
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KASSERT(tp->t_refcnt > 0,
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("ttyref(): tty refcnt is %d (%s)",
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tp->t_refcnt, tp->t_dev != NULL ? devtoname(tp->t_dev) : "??"));
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i = ++tp->t_refcnt;
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mtx_unlock(&tp->t_mtx);
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return (i);
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}
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/*
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* Drop a reference to a TTY.
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* When reference count drops to zero, we free it.
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*/
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int
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ttyrel(struct tty *tp)
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{
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int i;
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mtx_lock(&tty_list_mutex);
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mtx_lock(&tp->t_mtx);
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KASSERT(tp->t_refcnt > 0,
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("ttyrel(): tty refcnt is %d (%s)",
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tp->t_refcnt, tp->t_dev != NULL ? devtoname(tp->t_dev) : "??"));
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i = --tp->t_refcnt;
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if (i != 0) {
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mtx_unlock(&tp->t_mtx);
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mtx_unlock(&tty_list_mutex);
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return (i);
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}
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TAILQ_REMOVE(&tty_list, tp, t_list);
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mtx_unlock(&tp->t_mtx);
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mtx_unlock(&tty_list_mutex);
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mtx_destroy(&tp->t_mtx);
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free(tp, M_TTYS);
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return (i);
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}
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/*
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* Allocate a tty struct. Clists in the struct will be allocated by
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* ttyopen().
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@ -2637,35 +2690,45 @@ ttysleep(struct tty *tp, void *chan, int pri, char *wmesg, int timo)
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struct tty *
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ttymalloc(struct tty *tp)
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{
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static int once;
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if (tp)
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if (!once) {
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mtx_init(&tty_list_mutex, "ttylist", NULL, MTX_DEF);
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once++;
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}
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if (tp) {
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/*
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* XXX: Either this argument should go away, or we should
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* XXX: require it and do a ttyrel(tp) here and allocate
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* XXX: a new tty. For now do nothing.
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*/
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return(tp);
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}
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tp = malloc(sizeof *tp, M_TTYS, M_WAITOK | M_ZERO);
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tp->t_timeout = -1;
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SLIST_INSERT_HEAD(&tty_list, tp, t_list);
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mtx_init(&tp->t_mtx, "tty", NULL, MTX_DEF);
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tp->t_refcnt = 1;
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mtx_lock(&tty_list_mutex);
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TAILQ_INSERT_TAIL(&tty_list, tp, t_list);
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mtx_unlock(&tty_list_mutex);
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return (tp);
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}
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#if 0 /* XXX not yet usable: session leader holds a ref (see kern_exit.c). */
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/*
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* Free a tty struct. Clists in the struct should have been freed by
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* ttyclose().
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*/
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void
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ttyfree(struct tty *tp)
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{
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free(tp, M_TTYS);
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}
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#endif /* 0 */
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static int
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sysctl_kern_ttys(SYSCTL_HANDLER_ARGS)
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{
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struct tty *tp;
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struct tty *tp, *tp2;
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struct xtty xt;
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int error;
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SLIST_FOREACH(tp, &tty_list, t_list) {
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error = 0;
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mtx_lock(&tty_list_mutex);
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tp = TAILQ_FIRST(&tty_list);
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if (tp != NULL)
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ttyref(tp);
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mtx_unlock(&tty_list_mutex);
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while (tp != NULL) {
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bzero(&xt, sizeof xt);
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xt.xt_size = sizeof xt;
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#define XT_COPY(field) xt.xt_##field = tp->t_##field
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@ -2673,14 +2736,14 @@ sysctl_kern_ttys(SYSCTL_HANDLER_ARGS)
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xt.xt_cancc = tp->t_canq.c_cc;
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xt.xt_outcc = tp->t_outq.c_cc;
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XT_COPY(line);
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if (tp->t_dev)
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if (tp->t_dev != NULL)
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xt.xt_dev = dev2udev(tp->t_dev);
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XT_COPY(state);
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XT_COPY(flags);
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XT_COPY(timeout);
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if (tp->t_pgrp)
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if (tp->t_pgrp != NULL)
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xt.xt_pgid = tp->t_pgrp->pg_id;
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if (tp->t_session)
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if (tp->t_session != NULL)
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xt.xt_sid = tp->t_session->s_sid;
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XT_COPY(termios);
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XT_COPY(winsize);
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@ -2696,8 +2759,17 @@ sysctl_kern_ttys(SYSCTL_HANDLER_ARGS)
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XT_COPY(ospeedwat);
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#undef XT_COPY
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error = SYSCTL_OUT(req, &xt, sizeof xt);
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if (error)
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if (error != 0) {
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ttyrel(tp);
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return (error);
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}
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mtx_lock(&tty_list_mutex);
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tp2 = TAILQ_NEXT(tp, t_list);
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if (tp2 != NULL)
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ttyref(tp2);
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mtx_unlock(&tty_list_mutex);
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ttyrel(tp);
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tp = tp2;
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}
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return (0);
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}
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@ -49,6 +49,8 @@
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#include <sys/termios.h>
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#include <sys/queue.h>
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#include <sys/selinfo.h>
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#include <sys/_lock.h>
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#include <sys/_mutex.h>
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/*
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* Clists are character lists, which is a variable length linked list
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@ -110,7 +112,10 @@ struct tty {
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int t_olowat; /* Low water mark for output. */
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speed_t t_ospeedwat; /* t_ospeed override for watermarks. */
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int t_gen; /* Generation number. */
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SLIST_ENTRY(tty) t_list; /* Global chain of ttys for pstat(8) */
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TAILQ_ENTRY(tty) t_list; /* Global chain of ttys for pstat(8) */
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struct mtx t_mtx;
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int t_refcnt;
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};
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#define t_cc t_termios.c_cc
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@ -296,7 +301,6 @@ void ttychars(struct tty *tp);
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int ttycheckoutq(struct tty *tp, int wait);
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int ttyclose(struct tty *tp);
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void ttyflush(struct tty *tp, int rw);
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void ttyfree(struct tty *tp);
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void ttyinfo(struct tty *tp);
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int ttyinput(int c, struct tty *tp);
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int ttylclose(struct tty *tp, int flag);
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@ -304,6 +308,8 @@ int ttyldoptim(struct tty *tp);
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struct tty *ttymalloc(struct tty *tp);
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int ttymodem(struct tty *tp, int flag);
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int ttyopen(dev_t device, struct tty *tp);
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int ttyref(struct tty *tp);
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int ttyrel(struct tty *tp);
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int ttysleep(struct tty *tp, void *chan, int pri, char *wmesg, int timo);
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int ttywait(struct tty *tp);
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int unputc(struct clist *q);
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