There are some potential feefilter cleanups mentioned and motivated in comment https://github.com/bitcoin/bitcoin/pull/21509#issuecomment-805808485 . If you address the locking one, please be careful and make sure that `round()` is only called under a lock. See https://github.com/bitcoin/bitcoin/pull/21509#issuecomment-807992199

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MarkBlockAsReceived(resp.blockhash); 
                fBlockRead = true;
                
                
                
                
                
                
                mapBlockSource.emplace(resp.blockhash, std::make_pair(pfrom.GetId(), false));
            }
        } 
        if (fBlockRead) {
            
            
            
            
            
            
            ProcessBlock(pfrom, pblock, true);
        }
        return;
    }
    if (msg_type == NetMsgType::HEADERS)
    {
        
        if (fImporting || fReindex) {
            LogPrint(BCLog::NET, "Unexpected headers message received from peer %d\n", pfrom.GetId());