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dma-buf: Assign separate lockdep class to chain lock

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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: a408c0ca0c ("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: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patch.msgid.link/20260224183922.2256492-1-matthew.brost@intel.com
This commit is contained in:
Matthew Brost 2026-02-24 10:39:21 -08:00
parent 3d8fd28d05
commit 2ec8653555
1 changed files with 13 additions and 0 deletions
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13
drivers/dma-buf/dma-fence-chain.c
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@ -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.