Author: marcel
Date: Thu Oct 9 02:30:38 2014
New Revision: 272789
URL: https://svnweb.freebsd.org/changeset/base/272789
Log:
Fix draining in ttydev_leave():
1. ERESTART is not only returned when the revoke count changed. It
is also returned when a signal is received. While a change in
the revoke count should be ignored, a signal should not.
2. Waiting until the output queue is entirely drained can cause a
hang when the underlying device is stuck or broken.
Have tty_drain() take care of this by telling it when we're leaving.
When leaving, tty_drain() will use a timed wait to address point 2
above and it will check the revoke count to handle point 1 above.
The timeout is set to 1 second, which is arbitrary and long enough
to expect a change in the output queue.
Discussed with: jilles@
Reported by: Yamagi Burmeister <li...@yamagi.org>
Modified:
head/sys/kern/tty.c
Modified: head/sys/kern/tty.c
==============================================================================
--- head/sys/kern/tty.c Thu Oct 9 02:24:34 2014 (r272788)
+++ head/sys/kern/tty.c Thu Oct 9 02:30:38 2014 (r272789)
@@ -123,9 +123,10 @@ tty_watermarks(struct tty *tp)
}
static int
-tty_drain(struct tty *tp)
+tty_drain(struct tty *tp, int leaving)
{
- int error;
+ size_t bytesused;
+ int error, revokecnt;
if (ttyhook_hashook(tp, getc_inject))
/* buffer is inaccessible */
@@ -134,11 +135,27 @@ tty_drain(struct tty *tp)
while (ttyoutq_bytesused(&tp->t_outq) > 0) {
ttydevsw_outwakeup(tp);
/* Could be handled synchronously. */
- if (ttyoutq_bytesused(&tp->t_outq) == 0)
+ bytesused = ttyoutq_bytesused(&tp->t_outq);
+ if (bytesused == 0)
return (0);
/* Wait for data to be drained. */
- error = tty_wait(tp, &tp->t_outwait);
+ if (leaving) {
+ revokecnt = tp->t_revokecnt;
+ error = tty_timedwait(tp, &tp->t_outwait, hz);
+ switch (error) {
+ case ERESTART:
+ if (revokecnt != tp->t_revokecnt)
+ error = 0;
+ break;
+ case EWOULDBLOCK:
+ if (ttyoutq_bytesused(&tp->t_outq) < bytesused)
+ error = 0;
+ break;
+ }
+ } else
+ error = tty_wait(tp, &tp->t_outwait);
+
if (error)
return (error);
}
@@ -191,10 +208,8 @@ ttydev_leave(struct tty *tp)
/* Drain any output. */
MPASS((tp->t_flags & TF_STOPPED) == 0);
- if (!tty_gone(tp)) {
- while (tty_drain(tp) == ERESTART)
- ;
- }
+ if (!tty_gone(tp))
+ tty_drain(tp, 1);
ttydisc_close(tp);
@@ -1528,7 +1543,7 @@ tty_generic_ioctl(struct tty *tp, u_long
/* Set terminal flags through tcsetattr(). */
if (cmd == TIOCSETAW || cmd == TIOCSETAF) {
- error = tty_drain(tp);
+ error = tty_drain(tp, 0);
if (error)
return (error);
if (cmd == TIOCSETAF)
@@ -1707,7 +1722,7 @@ tty_generic_ioctl(struct tty *tp, u_long
}
case TIOCDRAIN:
/* Drain TTY output. */
- return tty_drain(tp);
+ return tty_drain(tp, 0);
case TIOCCONS:
/* Set terminal as console TTY. */
if (*(int *)data) {
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