[PATCH] uml: unregister useless console when it's not needed

-mm in combination with an FC5 init started dying with 'stderr=1' because init
didn't like the lack of /dev/console and exited.  The problem was that the
stderr console, which is intended to dump printk output to the terminal before
the regular console is initialized, isn't a tty, and so can't make
/dev/console operational.

However, since it is registered first, the normal console, when it is
registered, doesn't become the preferred console, and isn't attached to
/dev/console.  Thus, /dev/console is never operational.

This patch makes the stderr console unregister itself in an initcall, which is
late enough that the normal console is registered.  When that happens, the
normal console will become the preferred console and will be able to run
/dev/console.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/um/drivers/stderr_console.c

@@ -8,10 +8,7 @@
 
 /*
  * Don't register by default -- as this registeres very early in the
- * boot process it becomes the default console.  And as this isn't a
- * real tty driver init isn't able to open /dev/console then.
- *
- * In most cases this isn't what you want ...
+ * boot process it becomes the default console.
  */
 static int use_stderr_console = 0;
 
@@ -43,3 +40,20 @@ static int stderr_setup(char *str)
 	return 1;
 }
 __setup("stderr=", stderr_setup);
+
+/* The previous behavior of not unregistering led to /dev/console being
+ * impossible to open.  My FC5 filesystem started having init die, and the
+ * system panicing because of this.  Unregistering causes the real
+ * console to become the default console, and /dev/console can then be
+ * opened.  Making this an initcall makes this happen late enough that
+ * there is no added value in dumping everything to stderr, and the
+ * normal console is good enough to show you all available output.
+ */
+static int __init unregister_stderr(void)
+{
+	unregister_console(&stderr_console);
+
+	return 0;
+}
+
+__initcall(unregister_stderr);