Merge bitcoin/bitcoin#33264: threading: reduce the scope of lock in getblocktemplate

493ba0f threading: reduce the scope of lock in getblocktemplate (kevkevinpal)

Pull request description:

  This change was motivated by bitcoin/bitcoin#32592 (comment)

  It does exactly what is said in the comment. Reducing the scope of the lock by a bit before it is needed

ACKs for top commit:
  stickies-v:
    re-ACK 493ba0f
  maflcko:
    lgtm ACK 493ba0f

Tree-SHA512: aa3a21ef3da6be6c0af78aa2dda61ee21c3f6d4d9c897413dba9e7d7d2a91e9e069bbc6b6684b45aadaa28d8603dd310f2c2d2e58c31bb4d864204e468fefaf1

Author: fanquake

src/rpc/mining.cpp

@@ -704,8 +704,6 @@ static RPCHelpMan getblocktemplate()
     NodeContext& node = EnsureAnyNodeContext(request.context);
     ChainstateManager& chainman = EnsureChainman(node);
     Mining& miner = EnsureMining(node);
-    WAIT_LOCK(cs_main, csmain_lock);
-    uint256 tip{CHECK_NONFATAL(miner.getTip()).value().hash};
 
     std::string strMode = "template";
     UniValue lpval = NullUniValue;
@@ -735,6 +733,7 @@ static RPCHelpMan getblocktemplate()
                 throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Block decode failed");
 
             uint256 hash = block.GetHash();
+            LOCK(cs_main);
             const CBlockIndex* pindex = chainman.m_blockman.LookupBlockIndex(hash);
             if (pindex) {
                 if (pindex->IsValid(BLOCK_VALID_SCRIPTS))
@@ -773,6 +772,9 @@ static RPCHelpMan getblocktemplate()
     static unsigned int nTransactionsUpdatedLast;
     const CTxMemPool& mempool = EnsureMemPool(node);
 
+    WAIT_LOCK(cs_main, cs_main_lock);
+    uint256 tip{CHECK_NONFATAL(miner.getTip()).value().hash};
+
     // Long Polling (BIP22)
     if (!lpval.isNull()) {
         /**
@@ -811,7 +813,7 @@ static RPCHelpMan getblocktemplate()
 
         // Release lock while waiting
         {
-            REVERSE_LOCK(csmain_lock, cs_main);
+            REVERSE_LOCK(cs_main_lock, cs_main);
             MillisecondsDouble checktxtime{std::chrono::minutes(1)};
             while (IsRPCRunning()) {
                 // If hashWatchedChain is not a real block hash, this will