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bc1967f088
## Overview
This PR fixes a race condition during blockchain shutdown where snapshot
generation could continue accessing the trie database after it has been
closed, leading to iterator errors. We noticed this in one of our nodes
on https://github.com/ava-labs/avalanchego, which relies on an older
version of geth with the same issue (so this behavior does happen!).
During node shutdown, the following sequence occurs:
1. `BlockChain.Stop()` calls `snaps.Release()` to clean up snapshot
resources
2. `Release()` only resets the cache but doesn't stop the generator
goroutine
3. The trie database is then closed via `triedb.Close()`
4. The still-running generator attempts to iterate storage tries
5. Iterator fails because the database is closed (`"Generator failed to
iterate storage trie"`)
## Problem
There are three related bugs:
1. `Release()` doesn't stop generation: The `diskLayer.Release()` method
only resets the cache without stopping ongoing snapshot generation,
leaving the generator goroutine running after database closure.
2. `stopGeneration()` has an incorrect completion check: The
`stopGeneration()` method checks `genMarker != nil` to determine if
generation is running. However, `genMarker` is set to nil when
generation completes successfully, even though the generator goroutine
is still waiting for the abort signal at the end of `generate()`. See
line 705 in `generate.go`:
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|---|---|---|
| .. | ||
| abidump | ||
| abigen | ||
| blsync | ||
| devp2p | ||
| era | ||
| ethkey | ||
| evm | ||
| fetchpayload | ||
| geth | ||
| keeper | ||
| rlpdump | ||
| utils | ||
| workload | ||