[PATCH 096/139] fb: rework locking to fix lock ordering on takeover

From: Luis Henriques
Date: Thu Feb 28 2013 - 09:50:09 EST

3.5.7.7 -stable review patch. If anyone has any objections, please let me know.

------------------

From: Alan Cox <alan@xxxxxxxxxxxxxxx>

commit 50e244cc793d511b86adea24972f3a7264cae114 upstream.

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@xxxxxxxxxxxxxxxxxxxx: remove stray non-ascii char, tidy comment]
[akpm@xxxxxxxxxxxxxxxxxxxx: export do_take_over_console()]
[airlied: cleanup another non-ascii char]
Signed-off-by: Alan Cox <alan@xxxxxxxxxxxxxxx>
Cc: Florian Tobias Schandinat <FlorianSchandinat@xxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: Jiri Kosina <jkosina@xxxxxxx>
Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
drivers/tty/vt/vt.c | 93 ++++++++++++++++++++++++++++++++-----------
drivers/video/console/fbcon.c | 29 +++++++++++++-
drivers/video/fbmem.c | 5 +--
drivers/video/fbsysfs.c | 3 ++
include/linux/console.h | 1 +
5 files changed, 104 insertions(+), 27 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 3b4f5b6..f7ffae5 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -3017,7 +3017,7 @@ 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;
@@ -3028,7 +3028,7 @@ 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++) {
@@ -3113,11 +3113,22 @@ 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)
{
@@ -3229,9 +3240,9 @@ 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;
@@ -3522,28 +3533,18 @@ 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];

@@ -3596,10 +3597,29 @@ 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);

/**
@@ -3653,17 +3673,44 @@ 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
- Â* but not unregistered it.
- */
+ * but not unregistered it.
+ */
if (err == -EBUSY)
err = 0;
if (!err)
diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index bdcd34d..7ccec55 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -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;
@@ -3121,7 +3148,7 @@ 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)
diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 0dff12a..616278a 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -1651,7 +1651,9 @@ 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;
}
@@ -1854,11 +1856,8 @@ 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;
diff --git a/drivers/video/fbsysfs.c b/drivers/video/fbsysfs.c
index a55e366..ef476b0 100644
--- a/drivers/video/fbsysfs.c
+++ b/drivers/video/fbsysfs.c
@@ -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;
}
diff --git a/include/linux/console.h b/include/linux/console.h
index 7201ce4..e8ea7d7 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -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);
--
1.8.1.2

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