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Track state to determine if the associated TTY device node has been used.

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It turns out our old TTY layer (and other implementations) block when
you read() on a PTY master device of which the slave device node has not
been opened yet. Our new implementation just returned 0. This caused
applications like telnetd to die in a very subtle way (when child
processes would open the TTY later than the first call to select()).

Introduce a new flag called PTS_FINISHED, which indicates whether we
should block or bail out of a read() or write() occurs.

Reported by:	Claude Buisson <clbuisson orange fr>
This commit is contained in:
Ed Schouten 2008-09-23 17:12:25 +00:00
parent aaa6d7ebb9
commit b61637107c
1 changed files with 19 additions and 4 deletions
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21
sys/kern/tty_pts.c
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@ -82,6 +82,7 @@ struct pts_softc {
int pts_unit; /* (c) Device unit number. */
unsigned int pts_flags; /* (t) Device flags. */
#define PTS_PKT 0x1 /* Packet mode. */
#define PTS_FINISHED 0x2 /* Return errors on read()/write(). */
char pts_pkt; /* (t) Unread packet mode data. */
struct cv pts_inwait; /* (t) Blocking write() on master. */
@ -156,7 +157,7 @@ ptsdev_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
}
/* Maybe the device isn't used anyway. */
if (tty_opened(tp) == 0)
if (psc->pts_flags & PTS_FINISHED)
break;
/* Wait for more data. */
@ -224,7 +225,7 @@ ptsdev_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
}
/* Maybe the device isn't used anyway. */
if (tty_opened(tp) == 0) {
if (psc->pts_flags & PTS_FINISHED) {
error = EIO;
goto done;
}
@ -380,7 +381,7 @@ ptsdev_poll(struct file *fp, int events, struct ucred *active_cred,
tty_lock(tp);
if (tty_opened(tp) == 0) {
if (psc->pts_flags & PTS_FINISHED) {
/* Slave device is not opened. */
tty_unlock(tp);
return (events &
@ -503,13 +504,26 @@ ptsdrv_inwakeup(struct tty *tp)
selwakeup(&psc->pts_inpoll);
}
static int
ptsdrv_open(struct tty *tp)
{
struct pts_softc *psc = tty_softc(tp);
psc->pts_flags &= ~PTS_FINISHED;
return (0);
}
static void
ptsdrv_close(struct tty *tp)
{
struct pts_softc *psc = tty_softc(tp);
/* Wake up any blocked readers/writers. */
ptsdrv_outwakeup(tp);
ptsdrv_inwakeup(tp);
psc->pts_flags |= PTS_FINISHED;
}
static void
@ -565,6 +579,7 @@ static struct ttydevsw pts_class = {
.tsw_flags = TF_NOPREFIX,
.tsw_outwakeup = ptsdrv_outwakeup,
.tsw_inwakeup = ptsdrv_inwakeup,
.tsw_open = ptsdrv_open,
.tsw_close = ptsdrv_close,
.tsw_pktnotify = ptsdrv_pktnotify,
.tsw_free = ptsdrv_free,