Commit 1c8ce271 authored by Antonino A. Daplas's avatar Antonino A. Daplas Committed by Linus Torvalds
Browse files

[PATCH] Detaching fbcon: fix give_up_console() 



To allow for detaching fbcon, it must be able to give up the console.
However, the function give_up_console() is plain broken.  It just sets the
entries in the console driver map to NULL, it leaves the vt layer without a
console driver, and does not decrement the module reference count.  Calling
give_up_console() is guaranteed to hang the machine..

To fix this problem, ensure that the virtual consoles are not left dangling
without a driver.  All systems have a default boot driver (either vgacon or
dummycon) which is never unloaded.  For those vt's that lost their driver, the
default boot driver is reassigned back to them.

Signed-off-by: default avatarAntonino Daplas <adaplas@pol.net>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 50ec42ed

drivers/char/vt.c

+21 −8
Original line number Diff line number Diff line
@@ -100,6 +100,7 @@ 




const struct consw *conswitchp;

static struct consw *defcsw; /* default console */



/* A bitmap for codes <32. A bit of 1 indicates that the code

 * corresponding to that bit number invokes some special action
@@ -2673,17 +2674,23 @@ int take_over_console(const struct consw *csw, int first, int last, int deflt) 
	if (!try_module_get(owner))

		return -ENODEV;



	acquire_console_sem();

	/* save default console, for possible recovery later on */

	if (!defcsw)

		defcsw = (struct consw *) conswitchp;



	acquire_console_sem();

	desc = csw->con_startup();



	if (!desc) {

		release_console_sem();

		module_put(owner);

		return -ENODEV;

	}



	if (deflt) {

		if (conswitchp)

			module_put(conswitchp->owner);



		__module_get(owner);

		conswitchp = csw;

	}
@@ -2701,6 +2708,7 @@ int take_over_console(const struct consw *csw, int first, int last, int deflt) 
			continue;



		j = i;



		if (CON_IS_VISIBLE(vc)) {

			k = i;

			save_screen(vc);
@@ -2709,10 +2717,8 @@ int take_over_console(const struct consw *csw, int first, int last, int deflt) 
		old_was_color = vc->vc_can_do_color;

		vc->vc_sw->con_deinit(vc);

		vc->vc_origin = (unsigned long)vc->vc_screenbuf;

		vc->vc_visible_origin = vc->vc_origin;

		vc->vc_scr_end = vc->vc_origin + vc->vc_screenbuf_size;

		vc->vc_pos = vc->vc_origin + vc->vc_size_row * vc->vc_y + 2 * vc->vc_x;

		visual_init(vc, i, 0);

		set_origin(vc);

		update_attr(vc);



		/* If the console changed between mono <-> color, then
@@ -2741,22 +2747,29 @@ int take_over_console(const struct consw *csw, int first, int last, int deflt) 
		printk("to %s\n", desc);



	release_console_sem();



	module_put(owner);

	return 0;

}



void give_up_console(const struct consw *csw)

{

	int i;

	int i, first = -1, last = -1, deflt = 0;



	for (i = 0; i < MAX_NR_CONSOLES; i++)

		if (con_driver_map[i] == csw) {

			if (first == -1)

				first = i;

			last = i;

			module_put(csw->owner);

			con_driver_map[i] = NULL;

		}

}



	if (first != -1 && defcsw) {

		if (first == 0 && last == MAX_NR_CONSOLES - 1)

			deflt = 1;

		take_over_console(defcsw, first, last, deflt);

	}

}

#endif



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