[PATCH] [Fwd: Console locking and blanking]

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

I've had WARN_CONSOLE_UNLOCKED warnings when calling TIOCLINUX 
TIOCL_BLANKSCREEN and TIOCL_UNBLANKSCREEN.

(I'm blind and I use a braille display. I use those functions to blank 
my laptop's screen so people don't read it, and hopefully to conserve 
power.)

The warnings are from these places:
do_blank_screen at drivers/char/vt.c:2754 (Not tainted)
save_screen at drivers/char/vt.c:575 (Not tainted)
do_unblank_screen at drivers/char/vt.c:2822 (Not tainted)
set_palette at drivers/char/vt.c:2908 (Not tainted)

At a glance I would think the following patch ought to fix that. Tested on 
one machine. Could you please tell me if this is correct and/or forward 
the patch where appropriate...

Signed-off-by: Stéphane Doyon <s.doyon@videotron.ca>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

--- linux-2.6.12/drivers/char/vt.c.orig	2005-08-16 15:39:14.000000000 -0400
+++ linux-2.6.12/drivers/char/vt.c	2005-08-16 15:41:04.000000000 -0400
@@ -2272,7 +2272,9 @@
  			ret = paste_selection(tty);
  			break;
  		case TIOCL_UNBLANKSCREEN:
+			acquire_console_sem();
  			unblank_screen();
+			release_console_sem();
  			break;
  		case TIOCL_SELLOADLUT:
  			ret = sel_loadlut(p);
@@ -2317,8 +2319,10 @@
  			}
  			break;
  		case TIOCL_BLANKSCREEN:	/* until explicitly unblanked, not only poked */
+			acquire_console_sem();
  			ignore_poke = 1;
  			do_blank_screen(0);
+			release_console_sem();
  			break;
  		case TIOCL_BLANKEDSCREEN:
  			ret = console_blanked;