con_open() is called on every open of the tty, even if the tty is already all
set up.  We only need to do that initialisation if the tty is being set up
for the very first time (tty->count == 1).

So do that: check for tty_count == 1 inside console_sem() and if so, bypass
all the unnecessary initialisation.



---

 25-akpm/drivers/char/vt.c |   40 +++++++++++++++++++---------------------
 1 files changed, 19 insertions(+), 21 deletions(-)

diff -puN drivers/char/vt.c~con_open-speedup drivers/char/vt.c
--- 25/drivers/char/vt.c~con_open-speedup	2004-03-25 10:08:38.428019360 -0800
+++ 25-akpm/drivers/char/vt.c	2004-03-25 10:20:59.352381736 -0800
@@ -2454,32 +2454,30 @@ static void con_flush_chars(struct tty_s
 /*
  * Allocate the console screen memory.
  */
-static int con_open(struct tty_struct *tty, struct file * filp)
+static int con_open(struct tty_struct *tty, struct file *filp)
 {
-	unsigned int	currcons;
-	int i;
-
-	currcons = tty->index;
+	unsigned int currcons = tty->index;
+	int ret = 0;
 
 	acquire_console_sem();
-	i = vc_allocate(currcons);
-	if (i) {
-		release_console_sem();
-		return i;
+	if (tty->count == 1) {
+		ret = vc_allocate(currcons);
+		if (ret == 0) {
+			vt_cons[currcons]->vc_num = currcons;
+			tty->driver_data = vt_cons[currcons];
+			vc_cons[currcons].d->vc_tty = tty;
+
+			if (!tty->winsize.ws_row && !tty->winsize.ws_col) {
+				tty->winsize.ws_row = video_num_lines;
+				tty->winsize.ws_col = video_num_columns;
+			}
+			release_console_sem();
+			vcs_make_devfs(tty);
+			return ret;
+		}
 	}
-	vt_cons[currcons]->vc_num = currcons;
-	tty->driver_data = vt_cons[currcons];
-	vc_cons[currcons].d->vc_tty = tty;
-
 	release_console_sem();
-
-	if (!tty->winsize.ws_row && !tty->winsize.ws_col) {
-		tty->winsize.ws_row = video_num_lines;
-		tty->winsize.ws_col = video_num_columns;
-	}
-	if (tty->count == 1)
-		vcs_make_devfs(tty);
-	return 0;
+	return ret;
 }
 
 static void con_close(struct tty_struct *tty, struct file *filp)

_