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Commit 50e244cc authored by Alan Cox's avatar Alan Cox Committed by Dave Airlie
Browse files

fb: rework locking to fix lock ordering on takeover 



Adjust the console layer to allow a take over call where the caller
already holds the locks.  Make the fb layer lock in order.

This is partly a band aid, the fb layer is terminally confused about the
locking rules it uses for its notifiers it seems.

[akpm@linux-foundation.org: remove stray non-ascii char, tidy comment]
[akpm@linux-foundation.org: export do_take_over_console()]
[airlied: cleanup another non-ascii char]
Signed-off-by: default avatarAlan Cox <alan@linux.intel.com>
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: stable <stable@vger.kernel.org>
Tested-by: default avatarSedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent 84b603ab

drivers/tty/vt/vt.c

+70 −23
Original line number Diff line number Diff line
@@ -2987,7 +2987,7 @@ int __init vty_init(const struct file_operations *console_fops) 


static struct class *vtconsole_class;



static int bind_con_driver(const struct consw *csw, int first, int last,

static int do_bind_con_driver(const struct consw *csw, int first, int last,

			   int deflt)

{

	struct module *owner = csw->owner;
@@ -2998,7 +2998,7 @@ static int bind_con_driver(const struct consw *csw, int first, int last, 
	if (!try_module_get(owner))

		return -ENODEV;



	console_lock();

	WARN_CONSOLE_UNLOCKED();



	/* check if driver is registered */

	for (i = 0; i < MAX_NR_CON_DRIVER; i++) {
@@ -3083,11 +3083,22 @@ static int bind_con_driver(const struct consw *csw, int first, int last, 


	retval = 0;

err:

	console_unlock();

	module_put(owner);

	return retval;

};





static int bind_con_driver(const struct consw *csw, int first, int last,

			   int deflt)

{

	int ret;



	console_lock();

	ret = do_bind_con_driver(csw, first, last, deflt);

	console_unlock();

	return ret;

}



#ifdef CONFIG_VT_HW_CONSOLE_BINDING

static int con_is_graphics(const struct consw *csw, int first, int last)

{
@@ -3199,9 +3210,9 @@ int unbind_con_driver(const struct consw *csw, int first, int last, int deflt) 
	if (!con_is_bound(csw))

		con_driver->flag &= ~CON_DRIVER_FLAG_INIT;



	console_unlock();

	/* ignore return value, binding should not fail */

	bind_con_driver(defcsw, first, last, deflt);

	do_bind_con_driver(defcsw, first, last, deflt);

	console_unlock();

err:

	module_put(owner);

	return retval;
@@ -3492,28 +3503,18 @@ int con_debug_leave(void) 
}

EXPORT_SYMBOL_GPL(con_debug_leave);



/**

 * register_con_driver - register console driver to console layer

 * @csw: console driver

 * @first: the first console to take over, minimum value is 0

 * @last: the last console to take over, maximum value is MAX_NR_CONSOLES -1

 *

 * DESCRIPTION: This function registers a console driver which can later

 * bind to a range of consoles specified by @first and @last. It will

 * also initialize the console driver by calling con_startup().

 */

int register_con_driver(const struct consw *csw, int first, int last)

static int do_register_con_driver(const struct consw *csw, int first, int last)

{

	struct module *owner = csw->owner;

	struct con_driver *con_driver;

	const char *desc;

	int i, retval = 0;



	WARN_CONSOLE_UNLOCKED();



	if (!try_module_get(owner))

		return -ENODEV;



	console_lock();



	for (i = 0; i < MAX_NR_CON_DRIVER; i++) {

		con_driver = &registered_con_driver[i];
@@ -3566,10 +3567,29 @@ int register_con_driver(const struct consw *csw, int first, int last) 
	}



err:

	console_unlock();

	module_put(owner);

	return retval;

}



/**

 * register_con_driver - register console driver to console layer

 * @csw: console driver

 * @first: the first console to take over, minimum value is 0

 * @last: the last console to take over, maximum value is MAX_NR_CONSOLES -1

 *

 * DESCRIPTION: This function registers a console driver which can later

 * bind to a range of consoles specified by @first and @last. It will

 * also initialize the console driver by calling con_startup().

 */

int register_con_driver(const struct consw *csw, int first, int last)

{

	int retval;



	console_lock();

	retval = do_register_con_driver(csw, first, last);

	console_unlock();

	return retval;

}

EXPORT_SYMBOL(register_con_driver);



/**
@@ -3618,6 +3638,32 @@ err: 
}

EXPORT_SYMBOL(unregister_con_driver);



/*

 *	If we support more console drivers, this function is used

 *	when a driver wants to take over some existing consoles

 *	and become default driver for newly opened ones.

 *

 *	take_over_console is basically a register followed by unbind

 */

int do_take_over_console(const struct consw *csw, int first, int last, int deflt)

{

	int err;



	err = do_register_con_driver(csw, first, last);

	/*

	 * If we get an busy error we still want to bind the console driver

	 * and return success, as we may have unbound the console driver

	 * but not unregistered it.

	 */

	if (err == -EBUSY)

		err = 0;

	if (!err)

		do_bind_con_driver(csw, first, last, deflt);



	return err;

}

EXPORT_SYMBOL_GPL(do_take_over_console);



/*

 *	If we support more console drivers, this function is used

 *	when a driver wants to take over some existing consoles
@@ -3630,9 +3676,10 @@ int take_over_console(const struct consw *csw, int first, int last, int deflt) 
	int err;



	err = register_con_driver(csw, first, last);

	/* if we get an busy error we still want to bind the console driver

	/*

	 * If we get an busy error we still want to bind the console driver

	 * and return success, as we may have unbound the console driver

	 * but not unregistered it.

	 * but not unregistered it.

	 */

	if (err == -EBUSY)

		err = 0;

drivers/video/console/fbcon.c

+28 −1
Original line number Diff line number Diff line
@@ -529,6 +529,33 @@ static int search_for_mapped_con(void) 
	return retval;

}



static int do_fbcon_takeover(int show_logo)

{

	int err, i;



	if (!num_registered_fb)

		return -ENODEV;



	if (!show_logo)

		logo_shown = FBCON_LOGO_DONTSHOW;



	for (i = first_fb_vc; i <= last_fb_vc; i++)

		con2fb_map[i] = info_idx;



	err = do_take_over_console(&fb_con, first_fb_vc, last_fb_vc,

				fbcon_is_default);



	if (err) {

		for (i = first_fb_vc; i <= last_fb_vc; i++)

			con2fb_map[i] = -1;

		info_idx = -1;

	} else {

		fbcon_has_console_bind = 1;

	}



	return err;

}



static int fbcon_takeover(int show_logo)

{

	int err, i;
@@ -3115,7 +3142,7 @@ static int fbcon_fb_registered(struct fb_info *info) 
		}



		if (info_idx != -1)

			ret = fbcon_takeover(1);

			ret = do_fbcon_takeover(1);

	} else {

		for (i = first_fb_vc; i <= last_fb_vc; i++) {

			if (con2fb_map_boot[i] == idx)

drivers/video/fbmem.c

+2 −3
Original line number Diff line number Diff line
@@ -1650,7 +1650,9 @@ static int do_register_framebuffer(struct fb_info *fb_info) 
	event.info = fb_info;

	if (!lock_fb_info(fb_info))

		return -ENODEV;

	console_lock();

	fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event);

	console_unlock();

	unlock_fb_info(fb_info);

	return 0;

}
@@ -1853,11 +1855,8 @@ int fb_new_modelist(struct fb_info *info) 
	err = 1;



	if (!list_empty(&info->modelist)) {

		if (!lock_fb_info(info))

			return -ENODEV;

		event.info = info;

		err = fb_notifier_call_chain(FB_EVENT_NEW_MODELIST, &event);

		unlock_fb_info(info);

	}



	return err;

drivers/video/fbsysfs.c

+3 −0
Original line number Diff line number Diff line
@@ -177,6 +177,8 @@ static ssize_t store_modes(struct device *device, 
	if (i * sizeof(struct fb_videomode) != count)

		return -EINVAL;



	if (!lock_fb_info(fb_info))

		return -ENODEV;

	console_lock();

	list_splice(&fb_info->modelist, &old_list);

	fb_videomode_to_modelist((const struct fb_videomode *)buf, i,
@@ -188,6 +190,7 @@ static ssize_t store_modes(struct device *device, 
		fb_destroy_modelist(&old_list);



	console_unlock();

	unlock_fb_info(fb_info);



	return 0;

}

include/linux/console.h

+1 −0
Original line number Diff line number Diff line
@@ -78,6 +78,7 @@ int con_is_bound(const struct consw *csw); 
int register_con_driver(const struct consw *csw, int first, int last);

int unregister_con_driver(const struct consw *csw);

int take_over_console(const struct consw *sw, int first, int last, int deflt);

int do_take_over_console(const struct consw *sw, int first, int last, int deflt);

void give_up_console(const struct consw *sw);

#ifdef CONFIG_HW_CONSOLE

int con_debug_enter(struct vc_data *vc);