LoadChainTip requires cs_main to be locked. Under some conditions, it may call ActivateBestChain. However, ActivateBestChain requires cs_main NOT to be taken when called.
return g_chainstate.ActivateBestChain(state, chainparams, std::move(pblock));
}
bool CChainState::PreciousBlock(CValidationState& state, const CChainParams& params, CBlockIndex *pindex)
{
    {
        LOCK(cs_main);
        if (pindex->nChainWork < m_chain.Tip()->nChainWork) {
            
            return true;
        }
        if (m_chain.Tip()->nChainWork > nLastPreciousChainwork) {
            
            nBlockReverseSequenceId = -1;
        }
        nLastPreciousChainwork = m_chain.Tip()->nChainWork;
        setBlockIndexCandidates.erase(pindex);
        pindex->nSequenceId = nBlockReverseSequenceId;
        if (nBlockReverseSequenceId > std::numeric_limits<int32_t>::min()) {
            
            
            nBlockReverseSequenceId--;
        }
        if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS) && pindex->HaveTxsDownloaded()) {
            setBlockIndexCandidates.insert(pindex);
            PruneBlockIndexCandidates();
        }
    }
    return ActivateBestChain(state, params, std::shared_ptr<const CBlock>());
}
bool PreciousBlock(CValidationState& state, const CChainParams& params, CBlockIndex *pindex) {