Both the chain state and the transaction pool are validation specific, but access to them is protected by two locks. The two locks have the following semantics:

Backport of Bitcoin Core PR14963
https://github.com/bitcoin/bitcoin/pull/14963

1. Build with Clang in Debug mode:

CXX=clang++ CC=clang cmake .. -GNinja -DCMAKE_BUILD_TYPE=Debug
ninja check-all

2. Verify that the compiler has not emitted a thread-safety warning.
3. Run the node: ./src/bitcoind -regtest
4. Verify that text similar to "Assertion failed: lock ... not held ..." is not printed on stderr.

5. Run benchmarks:

cmake .. -GNinja
ninja bench-bitcoin
./src/bench/bitcoin-bench