Author: ed
Date: Sun May 24 12:32:03 2009
New Revision: 192682
URL: http://svn.freebsd.org/changeset/base/192682
Log:
Block when initially opening a TTY multiple times.
In the original MPSAFE TTY code, I changed the behaviour by returning
EBUSY. I thought this made more sense, because it's basically a race to
see who gets the TTY first.
It turns out this is not a good change, because it also causes EBUSY to
be returned when another process is closing the TTY. This can happen
during startup, when /etc/rc (or one of its children) is still busy
draining its data and /sbin/init is attempting to open the TTY to spawn
a getty.
Reported by: bz
Tested by: bz
Modified:
head/sys/kern/tty.c
Modified: head/sys/kern/tty.c
==============================================================================
--- head/sys/kern/tty.c Sun May 24 12:28:38 2009 (r192681)
+++ head/sys/kern/tty.c Sun May 24 12:32:03 2009 (r192682)
@@ -206,6 +206,7 @@ ttydev_leave(struct tty *tp)
ttydevsw_close(tp);
tp->t_flags &= ~TF_OPENCLOSE;
+ cv_broadcast(&tp->t_dcdwait);
tty_rel_free(tp);
}
@@ -231,13 +232,17 @@ ttydev_open(struct cdev *dev, int oflags
tty_unlock(tp);
return (ENXIO);
}
+
/*
- * Prevent the TTY from being opened when being torn down or
- * built up by unrelated processes.
+ * Block when other processes are currently opening or closing
+ * the TTY.
*/
- if (tp->t_flags & TF_OPENCLOSE) {
- tty_unlock(tp);
- return (EBUSY);
+ while (tp->t_flags & TF_OPENCLOSE) {
+ error = tty_wait(tp, &tp->t_dcdwait);
+ if (error != 0) {
+ tty_unlock(tp);
+ return (error);
+ }
}
tp->t_flags |= TF_OPENCLOSE;
@@ -299,6 +304,7 @@ ttydev_open(struct cdev *dev, int oflags
tp->t_flags |= TF_OPENED_IN;
done: tp->t_flags &= ~TF_OPENCLOSE;
+ cv_broadcast(&tp->t_dcdwait);
ttydev_leave(tp);
return (error);
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