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Remove double-locking deadlock from HTTP API (#4687)

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## Issue Addressed

Fix a deadlock introduced in #4236 which was caught during the v4.4.0 release testing cycle (with thanks to @paulhauner and `gdb`).

## Proposed Changes

Avoid re-locking the fork choice read lock when querying a state by root in the HTTP API. This avoids a deadlock due to the lock already being held.

## Additional Info

The [RwLock docs](https://docs.rs/lock_api/latest/lock_api/struct.RwLock.html#method.read) explicitly advise against re-locking:

> Note that attempts to recursively acquire a read lock on a RwLock when the current thread already holds one may result in a deadlock.
This commit is contained in:
Michael Sproul 2023-08-31 11:18:00 +00:00
parent e99ba3a14e
commit 74eb267643
1 changed files with 1 additions and 3 deletions
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4
beacon_node/http_api/src/state_id.rs
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@ -89,9 +89,7 @@ impl StateId {
} else { } else {
// This block is either old and finalized, or recent and unfinalized, so // This block is either old and finalized, or recent and unfinalized, so
// it's safe to fallback to the optimistic status of the finalized block. // it's safe to fallback to the optimistic status of the finalized block.
chain fork_choice
.canonical_head
.fork_choice_read_lock()
.is_optimistic_or_invalid_block(&hot_summary.latest_block_root) .is_optimistic_or_invalid_block(&hot_summary.latest_block_root)
.map_err(BeaconChainError::ForkChoiceError) .map_err(BeaconChainError::ForkChoiceError)
.map_err(warp_utils::reject::beacon_chain_error)? .map_err(warp_utils::reject::beacon_chain_error)?