Avoid holding cs_most_recent_block while calling ReadBlockFromDisk

src/net_processing.cpp

@@ -2894,6 +2894,8 @@ bool SendMessages(CNode* pto, CConnman& connman, std::atomic<bool>& interruptMsg
 
                     int nSendFlags = state.fWantsCmpctWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS;
 
+                    bool fGotBlockFromCache = false;
+                    {
                         LOCK(cs_most_recent_block);
                         if (most_recent_block_hash == pBestIndex->GetBlockHash()) {
                             if (state.fWantsCmpctWitness)
@@ -2902,7 +2904,10 @@ bool SendMessages(CNode* pto, CConnman& connman, std::atomic<bool>& interruptMsg
                                 CBlockHeaderAndShortTxIDs cmpctblock(*most_recent_block, state.fWantsCmpctWitness);
                                 connman.PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
                             }
-                    } else {
+                            fGotBlockFromCache = true;
+                        }
+                    }
+                    if (!fGotBlockFromCache) {
                         CBlock block;
                         bool ret = ReadBlockFromDisk(block, pBestIndex, consensusParams);
                         assert(ret);