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>

3 files changed, 33 insertions, 4 deletions

diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index fdefa8fd72c4..4bd7820cf4d0 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;
@@ -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)
diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 3ff0105a496a..d8d9831b3fdb 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -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;
diff --git a/drivers/video/fbsysfs.c b/drivers/video/fbsysfs.c
index a55e3669d135..ef476b02fbe5 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;
 }