[media] media-device: get rid of the spinlock

Right now, the lock schema for media_device struct is messy,
since sometimes, it is protected via a spin lock, while, for
media graph traversal, it is protected by a mutex.

Solve this conflict by always using a mutex.

As a side effect, this prevents a bug when the media notifiers
is called at atomic context, while running the notifier callback:

 BUG: sleeping function called from invalid context at mm/slub.c:1289
 in_atomic(): 1, irqs_disabled(): 0, pid: 3479, name: modprobe
 4 locks held by modprobe/3479:
 #0:  (&dev->mutex){......}, at: [<ffffffff81ce8933>] __driver_attach+0xa3/0x160
 #1:  (&dev->mutex){......}, at: [<ffffffff81ce8941>] __driver_attach+0xb1/0x160
 #2:  (register_mutex#5){+.+.+.}, at: [<ffffffffa10596c7>] usb_audio_probe+0x257/0x1c90 [snd_usb_audio]
 #3:  (&(&mdev->lock)->rlock){+.+.+.}, at: [<ffffffffa0e6051b>] media_device_register_entity+0x1cb/0x700 [media]
 CPU: 2 PID: 3479 Comm: modprobe Not tainted 4.5.0-rc3+ #49
 Hardware name:                  /NUC5i7RYB, BIOS RYBDWi35.86A.0350.2015.0812.1722 08/12/2015
 0000000000000000 ffff8803b3f6f288 ffffffff81933901 ffff8803c4bae000
 ffff8803c4bae5c8 ffff8803b3f6f2b0 ffffffff811c6af5 ffff8803c4bae000
 ffffffff8285d7f6 0000000000000509 ffff8803b3f6f2f0 ffffffff811c6ce5
 Call Trace:
 [<ffffffff81933901>] dump_stack+0x85/0xc4
 [<ffffffff811c6af5>] ___might_sleep+0x245/0x3a0
 [<ffffffff811c6ce5>] __might_sleep+0x95/0x1a0
 [<ffffffff8155aade>] kmem_cache_alloc_trace+0x20e/0x300
 [<ffffffffa0e66e3d>] ? media_add_link+0x4d/0x140 [media]
 [<ffffffffa0e66e3d>] media_add_link+0x4d/0x140 [media]
 [<ffffffffa0e69931>] media_create_pad_link+0xa1/0x600 [media]
 [<ffffffffa0fe11b3>] au0828_media_graph_notify+0x173/0x360 [au0828]
 [<ffffffffa0e68a6a>] ? media_gobj_create+0x1ba/0x480 [media]
 [<ffffffffa0e606fb>] media_device_register_entity+0x3ab/0x700 [media]

Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

1 files changed, 8 insertions, 8 deletions

diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c
index e95070b3a3d4..c53c1d5589a0 100644
--- a/drivers/media/media-entity.c
+++ b/drivers/media/media-entity.c
@@ -219,7 +219,7 @@ int media_entity_pads_init(struct media_entity *entity, u16 num_pads,
 	entity->pads = pads;
 
 	if (mdev)
-		spin_lock(&mdev->lock);
+		mutex_lock(&mdev->graph_mutex);
 
 	for (i = 0; i < num_pads; i++) {
 		pads[i].entity = entity;
@@ -230,7 +230,7 @@ int media_entity_pads_init(struct media_entity *entity, u16 num_pads,
 	}
 
 	if (mdev)
-		spin_unlock(&mdev->lock);
+		mutex_unlock(&mdev->graph_mutex);
 
 	return 0;
 }
@@ -747,9 +747,9 @@ void media_entity_remove_links(struct media_entity *entity)
 	if (mdev == NULL)
 		return;
 
-	spin_lock(&mdev->lock);
+	mutex_lock(&mdev->graph_mutex);
 	__media_entity_remove_links(entity);
-	spin_unlock(&mdev->lock);
+	mutex_unlock(&mdev->graph_mutex);
 }
 EXPORT_SYMBOL_GPL(media_entity_remove_links);
 
@@ -951,9 +951,9 @@ void media_remove_intf_link(struct media_link *link)
 	if (mdev == NULL)
 		return;
 
-	spin_lock(&mdev->lock);
+	mutex_lock(&mdev->graph_mutex);
 	__media_remove_intf_link(link);
-	spin_unlock(&mdev->lock);
+	mutex_unlock(&mdev->graph_mutex);
 }
 EXPORT_SYMBOL_GPL(media_remove_intf_link);
 
@@ -975,8 +975,8 @@ void media_remove_intf_links(struct media_interface *intf)
 	if (mdev == NULL)
 		return;
 
-	spin_lock(&mdev->lock);
+	mutex_lock(&mdev->graph_mutex);
 	__media_remove_intf_links(intf);
-	spin_unlock(&mdev->lock);
+	mutex_unlock(&mdev->graph_mutex);
 }
 EXPORT_SYMBOL_GPL(media_remove_intf_links);