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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: Alan 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: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Alan Cox 2013-01-25 10:28:15 +10:00 committed by Dave Airlie
parent 84b603abd2
commit 50e244cc79
5 changed files with 104 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

93
drivers/tty/vt/vt.c
View File

@ -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);
/**
@ -3623,17 +3643,44 @@ EXPORT_SYMBOL(unregister_con_driver);
* 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
* 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
* and become default driver for newly opened ones.
*
* take_over_console is basically a register followed by unbind
*/
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;
if (!err)

29
drivers/video/console/fbcon.c
View File

@ -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)

5
drivers/video/fbmem.c
View File

@ -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;

3
drivers/video/fbsysfs.c
View File

@ -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;
}

1
include/linux/console.h
View File

@ -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);