[PATCH] dma-buf: Give dma-fence-array distinct lockclasses

[Chris Wilson]

In order to allow dma-fence-array as a generic container for fences, we
need to allow for it to contain other dma-fence-arrays. By giving each
dma-fence-array construction their own lockclass, we allow different
types of dma-fence-array to nest, but still do not allow on class of
dma-fence-array to contain itself (even though they have distinct
locks).

In practice, this means that each subsystem gets its own dma-fence-array
class and we can freely use dma-fence-arrays as containers within the
dmabuf core without angering lockdep.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Christian König <christian.koenig at amd.com>
Cc: Daniel Vetter <daniel at ffwll.ch>
---
 drivers/dma-buf/dma-fence-array.c | 13 ++++++++-----
 include/linux/dma-fence-array.h   | 16 ++++++++++++----
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c
index d3fbd950be94..d9bcdbb66d46 100644
--- a/drivers/dma-buf/dma-fence-array.c
+++ b/drivers/dma-buf/dma-fence-array.c
@@ -147,10 +147,11 @@ EXPORT_SYMBOL(dma_fence_array_ops);
  * If @signal_on_any is true the fence array signals if any fence in the array
  * signals, otherwise it signals when all fences in the array signal.
  */
-struct dma_fence_array *dma_fence_array_create(int num_fences,
-					       struct dma_fence **fences,
-					       u64 context, unsigned seqno,
-					       bool signal_on_any)
+struct dma_fence_array *__dma_fence_array_create(int num_fences,
+						 struct dma_fence **fences,
+						 u64 context, unsigned seqno,
+						 bool signal_on_any,
+						 struct lock_class_key *key)
 {
 	struct dma_fence_array *array;
 	size_t size = sizeof(*array);
@@ -162,6 +163,8 @@ struct dma_fence_array *dma_fence_array_create(int num_fences,
 		return NULL;
 
 	spin_lock_init(&array->lock);
+	lockdep_set_class(&array->lock, key);
+
 	dma_fence_init(&array->base, &dma_fence_array_ops, &array->lock,
 		       context, seqno);
 	init_irq_work(&array->work, irq_dma_fence_array_work);
@@ -174,7 +177,7 @@ struct dma_fence_array *dma_fence_array_create(int num_fences,
 
 	return array;
 }
-EXPORT_SYMBOL(dma_fence_array_create);
+EXPORT_SYMBOL(__dma_fence_array_create);
 
 /**
  * dma_fence_match_context - Check if all fences are from the given context
diff --git a/include/linux/dma-fence-array.h b/include/linux/dma-fence-array.h
index 303dd712220f..1395f9428cdb 100644
--- a/include/linux/dma-fence-array.h
+++ b/include/linux/dma-fence-array.h
@@ -74,10 +74,18 @@ to_dma_fence_array(struct dma_fence *fence)
 	return container_of(fence, struct dma_fence_array, base);
 }
 
-struct dma_fence_array *dma_fence_array_create(int num_fences,
-					       struct dma_fence **fences,
-					       u64 context, unsigned seqno,
-					       bool signal_on_any);
+#define dma_fence_array_create(num, fences, context, seqno, any) ({ \
+	static struct lock_class_key __key;			\
+								\
+	__dma_fence_array_create((num), (fences), (context), (seqno), (any), \
+		        	 &__key);			\
+})
+
+struct dma_fence_array *__dma_fence_array_create(int num_fences,
+						 struct dma_fence **fences,
+						 u64 context, unsigned seqno,
+						 bool signal_on_any,
+						 struct lock_class_key *key);
 
 bool dma_fence_match_context(struct dma_fence *fence, u64 context);
 
-- 
2.23.0