Commit 2ec86535 authored by Matthew Brost's avatar Matthew Brost
Browse files

dma-buf: Assign separate lockdep class to chain lock 



dma_fence_chain_enable_signaling() and runs while holding the chain
inline_lock and may add callbacks to underlying fences, which takes
their inline_lock.

Since both locks share the same lockdep class, this valid nesting
triggers a recursive locking warning. Assign a distinct lockdep class
to the chain inline_lock so lockdep can correctly model the hierarchy.

Fixes: a408c0ca ("dma-buf: use inline lock for the dma-fence-chain")
Cc: Christian König <christian.koenig@amd.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Philipp Stanner <phasta@kernel.org>
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: default avatarMatthew Brost <matthew.brost@intel.com>
Reviewed-by: default avatarChristian König <christian.koenig@amd.com>
Link: https://patch.msgid.link/20260224183922.2256492-1-matthew.brost@intel.com
parent 3d8fd28d

drivers/dma-buf/dma-fence-chain.c

+13 −0
Original line number Diff line number Diff line
@@ -242,6 +242,7 @@ void dma_fence_chain_init(struct dma_fence_chain *chain, 
			  struct dma_fence *fence,

			  uint64_t seqno)

{

	static struct lock_class_key dma_fence_chain_lock_key;

	struct dma_fence_chain *prev_chain = to_dma_fence_chain(prev);

	uint64_t context;
@@ -263,6 +264,18 @@ void dma_fence_chain_init(struct dma_fence_chain *chain, 
	dma_fence_init64(&chain->base, &dma_fence_chain_ops, NULL,

			 context, seqno);



	/*

	 * dma_fence_chain_enable_signaling() is invoked while holding

	 * chain->base.inline_lock and may call dma_fence_add_callback()

	 * on the underlying fences, which takes their inline_lock.

	 *

	 * Since both locks share the same lockdep class, this legitimate

	 * nesting confuses lockdep and triggers a recursive locking

	 * warning. Assign a separate lockdep class to the chain lock

	 * to model this hierarchy correctly.

	 */

	lockdep_set_class(&chain->base.inline_lock, &dma_fence_chain_lock_key);



	/*

	 * Chaining dma_fence_chain container together is only allowed through

	 * the prev fence and not through the contained fence.