dma_fence_chain_enable_signaling() 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: a408c0ca0c41 ("dma-buf: use inline lock for the dma-fence-chain")
Cc: Christian König <[email protected]>
Cc: Tvrtko Ursulin <[email protected]>
Cc: Philipp Stanner <[email protected]>
Cc: Boris Brezillon <[email protected]>
Signed-off-by: Matthew Brost <[email protected]>
---
drivers/dma-buf/dma-fence-chain.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/drivers/dma-buf/dma-fence-chain.c
b/drivers/dma-buf/dma-fence-chain.c
index a707792b6025..4c2a9f2ce126 100644
--- a/drivers/dma-buf/dma-fence-chain.c
+++ b/drivers/dma-buf/dma-fence-chain.c
@@ -242,6 +242,9 @@ void dma_fence_chain_init(struct dma_fence_chain *chain,
struct dma_fence *fence,
uint64_t seqno)
{
+#if IS_ENABLED(CONFIG_LOCKDEP)
+ static struct lock_class_key dma_fence_chain_lock_key;
+#endif
struct dma_fence_chain *prev_chain = to_dma_fence_chain(prev);
uint64_t context;
@@ -263,6 +266,20 @@ void dma_fence_chain_init(struct dma_fence_chain *chain,
dma_fence_init64(&chain->base, &dma_fence_chain_ops, NULL,
context, seqno);
+#if IS_ENABLED(CONFIG_LOCKDEP)
+ /*
+ * 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);
+#endif
+
/*
* Chaining dma_fence_chain container together is only allowed through
* the prev fence and not through the contained fence.
--
2.34.1
