Re-implement virtual console (constty).

Protect conscallout with tty lock instead of Giant.  In addition to
Giant removal it also closes race on console unset.

Introduce additional lock to protect against concurrent console sets.

Remove consbuf free on console unset as unsafe, making impossible to
change buffer size after first allocation.  Instead increase default
buffer size from 8KB to 64KB and processing rate from 5Hz to 10-15Hz
to make the output more smooth.

MFC after:	1 month

1 files changed, 5 insertions, 19 deletions

diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index 8700eb8f9ef1..8dfe5e93780f 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -241,8 +241,7 @@ ttydev_leave(struct tty *tp)
 	tp->t_flags |= TF_OPENCLOSE;
 
 	/* Remove console TTY. */
-	if (constty == tp)
-		constty_clear();
+	constty_clear(tp);
 
 	/* Drain any output. */
 	if (!tty_gone(tp))
@@ -1920,24 +1919,11 @@ tty_generic_ioctl(struct tty *tp, u_long cmd, void *data, int fflag,
 			error = priv_check(td, PRIV_TTY_CONSOLE);
 			if (error)
 				return (error);
-
-			/*
-			 * XXX: constty should really need to be locked!
-			 * XXX: allow disconnected constty's to be stolen!
-			 */
-
-			if (constty == tp)
-				return (0);
-			if (constty != NULL)
-				return (EBUSY);
-
-			tty_unlock(tp);
-			constty_set(tp);
-			tty_lock(tp);
-		} else if (constty == tp) {
-			constty_clear();
+			error = constty_set(tp);
+		} else {
+			error = constty_clear(tp);
 		}
-		return (0);
+		return (error);
 	case TIOCGWINSZ:
 		/* Obtain window size. */
 		*(struct winsize*)data = tp->t_winsize;