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>
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 8fd8968..c076af0 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -2987,7 +2987,7 @@
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 @@
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 @@
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 @@
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 @@
}
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 = ®istered_con_driver[i];
@@ -3566,10 +3567,29 @@
}
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 @@
* 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)