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Commit 39e16ba1 authored by Christian König's avatar Christian König Committed by Alex Deucher
Browse files

dma-buf: make reservation_object_copy_fences rcu save 



Stop requiring that the src reservation object is locked for this operation.

Acked-by: default avatarChunming Zhou <david1.zhou@amd.com>
Signed-off-by: default avatarChristian König <christian.koenig@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1504551766-5093-1-git-send-email-deathsimple@vodafone.de
parent 6d281b1f

drivers/dma-buf/reservation.c

+42 −14
Original line number Diff line number Diff line
@@ -266,8 +266,7 @@ EXPORT_SYMBOL(reservation_object_add_excl_fence); 
* @dst: the destination reservation object

* @src: the source reservation object

*

* Copy all fences from src to dst. Both src->lock as well as dst-lock must be

* held.

* Copy all fences from src to dst. dst-lock must be held.

*/

int reservation_object_copy_fences(struct reservation_object *dst,

				   struct reservation_object *src)
@@ -277,33 +276,62 @@ int reservation_object_copy_fences(struct reservation_object *dst, 
	size_t size;

	unsigned i;



	src_list = reservation_object_get_list(src);

	rcu_read_lock();

	src_list = rcu_dereference(src->fence);



retry:

	if (src_list) {

		size = offsetof(typeof(*src_list),

				shared[src_list->shared_count]);

		unsigned shared_count = src_list->shared_count;



		size = offsetof(typeof(*src_list), shared[shared_count]);

		rcu_read_unlock();



		dst_list = kmalloc(size, GFP_KERNEL);

		if (!dst_list)

			return -ENOMEM;



		dst_list->shared_count = src_list->shared_count;

		dst_list->shared_max = src_list->shared_count;

		for (i = 0; i < src_list->shared_count; ++i)

			dst_list->shared[i] =

				dma_fence_get(src_list->shared[i]);

		rcu_read_lock();

		src_list = rcu_dereference(src->fence);

		if (!src_list || src_list->shared_count > shared_count) {

			kfree(dst_list);

			goto retry;

		}



		dst_list->shared_count = 0;

		dst_list->shared_max = shared_count;

		for (i = 0; i < src_list->shared_count; ++i) {

			struct dma_fence *fence;



			fence = rcu_dereference(src_list->shared[i]);

			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,

				     &fence->flags))

				continue;



			if (!dma_fence_get_rcu(fence)) {

				kfree(dst_list);

				src_list = rcu_dereference(src->fence);

				goto retry;

			}



			if (dma_fence_is_signaled(fence)) {

				dma_fence_put(fence);

				continue;

			}



			dst_list->shared[dst_list->shared_count++] = fence;

		}

	} else {

		dst_list = NULL;

	}



	new = dma_fence_get_rcu_safe(&src->fence_excl);

	rcu_read_unlock();



	kfree(dst->staged);

	dst->staged = NULL;



	src_list = reservation_object_get_list(dst);



	old = reservation_object_get_excl(dst);

	new = reservation_object_get_excl(src);



	dma_fence_get(new);



	preempt_disable();

	write_seqcount_begin(&dst->seq);