staging: bcm2835-camera: Replace spinlock protecting context_map with mutex

The commit "staging: bcm2835-camera: Replace open-coded idr with a struct idr."
replaced an internal implementation of an idr with the standard functions
and a spinlock. idr_alloc(GFP_KERNEL) can sleep whilst calling kmem_cache_alloc
to allocate the new node, but this is not valid whilst in an atomic context
due to the spinlock.

There is no need for this to be a spinlock as a standard mutex is
sufficient.

Fixes: 950fd867 ("staging: bcm2835-camera: Replace open-coded idr with a struct idr.")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/bcm2835-camera/mmal-vchiq.c

@@ -161,7 +161,8 @@ struct vchiq_mmal_instance {
 	void *bulk_scratch;
 
 	struct idr context_map;
-	spinlock_t context_map_lock;
+	/* protect accesses to context_map */
+	struct mutex context_map_lock;
 
 	/* component to use next */
 	int component_idx;
@@ -184,10 +185,10 @@ get_msg_context(struct vchiq_mmal_instance *instance)
 	 * that when we service the VCHI reply, we can look up what
 	 * message is being replied to.
 	 */
-	spin_lock(&instance->context_map_lock);
+	mutex_lock(&instance->context_map_lock);
 	handle = idr_alloc(&instance->context_map, msg_context,
 			   0, 0, GFP_KERNEL);
-	spin_unlock(&instance->context_map_lock);
+	mutex_unlock(&instance->context_map_lock);
 
 	if (handle < 0) {
 		kfree(msg_context);
@@ -211,9 +212,9 @@ release_msg_context(struct mmal_msg_context *msg_context)
 {
 	struct vchiq_mmal_instance *instance = msg_context->instance;
 
-	spin_lock(&instance->context_map_lock);
+	mutex_lock(&instance->context_map_lock);
 	idr_remove(&instance->context_map, msg_context->handle);
-	spin_unlock(&instance->context_map_lock);
+	mutex_unlock(&instance->context_map_lock);
 	kfree(msg_context);
 }
 
@@ -1849,7 +1850,7 @@ int vchiq_mmal_init(struct vchiq_mmal_instance **out_instance)
 
 	instance->bulk_scratch = vmalloc(PAGE_SIZE);
 
-	spin_lock_init(&instance->context_map_lock);
+	mutex_init(&instance->context_map_lock);
 	idr_init_base(&instance->context_map, 1);
 
 	params.callback_param = instance;