rpc: reduce LOCK(cs_main) scope in GetBlockChecked and getblock

Author: andrewtoth

src/rpc/blockchain.cpp

@@ -579,18 +579,20 @@ static RPCHelpMan getblockheader()
     };
 }
 
-static CBlock GetBlockChecked(BlockManager& blockman, const CBlockIndex* pblockindex) EXCLUSIVE_LOCKS_REQUIRED(::cs_main)
+static CBlock GetBlockChecked(BlockManager& blockman, const CBlockIndex* pblockindex)
 {
-    AssertLockHeld(::cs_main);
     CBlock block;
-    if (blockman.IsBlockPruned(pblockindex)) {
-        throw JSONRPCError(RPC_MISC_ERROR, "Block not available (pruned data)");
+    {
+        LOCK(cs_main);
+        if (blockman.IsBlockPruned(pblockindex)) {
+            throw JSONRPCError(RPC_MISC_ERROR, "Block not available (pruned data)");
+        }
     }
 
     if (!ReadBlockFromDisk(block, pblockindex, Params().GetConsensus())) {
         // Block not found on disk. This could be because we have the block
         // header in our index but not yet have the block or did not accept the
-        // block.
+        // block. Or if the block was pruned right after we released the lock above.
         throw JSONRPCError(RPC_MISC_ERROR, "Block not found on disk");
     }
 
@@ -721,7 +723,6 @@ static RPCHelpMan getblock()
         }
     }
 
-    CBlock block;
     const CBlockIndex* pblockindex;
     const CBlockIndex* tip;
     ChainstateManager& chainman = EnsureAnyChainman(request.context);
@@ -733,10 +734,10 @@ static RPCHelpMan getblock()
         if (!pblockindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
-
-        block = GetBlockChecked(chainman.m_blockman, pblockindex);
     }
 
+    const CBlock block{GetBlockChecked(chainman.m_blockman, pblockindex)};
+
     if (verbosity <= 0)
     {
         CDataStream ssBlock(SER_NETWORK, PROTOCOL_VERSION | RPCSerializationFlags());