fbcon: delay the start of the cursor timer until a con_switch()

As reported in Bugzilla Bug 9093, upon switching to X, a small rectangular
cursor can still be seen blinking in the upper left part of the screen.  It is
fbcon's text cursor.  This is caused by a strange ioctl(..., KDSETMODE,
KD_TEXT) call done by something in userspace, perhaps by X itself, while the
tty is still in graphics mode.  And when the tty is in KD_TEXT mode, the
cursor timer is restarted.

Although this is a userspace problem, we can work around it by delaying the
restart of the cursor timer until an fbcon_switch() is called.  In other
words, the cursor timer will not be restarted even if a KD_TEXT mode switch is
requested.

Regression potential: Present but low

Signed-off-by: Antonino Daplas <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

drivers/video/console/fbcon.c

@@ -2405,7 +2405,7 @@ static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch)
 			update_screen(vc);
 	}
 
-	if (fbcon_is_inactive(vc, info) ||
+	if (mode_switch || fbcon_is_inactive(vc, info) ||
 	    ops->blank_state != FB_BLANK_UNBLANK)
 		fbcon_del_cursor_timer(info);
 	else