fb: rework locking to fix lock ordering on takeover

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@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>
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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

3 files changed, 33 insertions, 4 deletions

diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index b27a91c..18d02c6 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -530,6 +530,33 @@ 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;
@@ -3122,7 +3149,7 @@ 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 7a41220..a94edc3 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -1628,7 +1628,9 @@ 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;
 }
@@ -1831,11 +1833,8 @@ 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 67afa9c..303fb9f 100644
--- a/drivers/video/fbsysfs.c
+++ b/drivers/video/fbsysfs.c
@@ -175,6 +175,8 @@ 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,
@@ -186,6 +188,7 @@ static ssize_t store_modes(struct device *device,
 		fb_destroy_modelist(&old_list);
 
 	console_unlock();
+	unlock_fb_info(fb_info);
 
 	return 0;
 }