Merge #12330: Reduce scope of cs_main and cs_wallet locks in listtransactions

c409b1a [rpc] Reduce scope of cs_main and cs_wallet locks in listtransactions (João Barbosa)

Pull request description:

  Trivial change, no behaviour change.

  Benchmark done as follow:
   - run with `-regtest`
   - wallet with 5000 transactions
   - measured the time spent with the lock and the total time
   - times are an average of 100 `listtransactions --count=...` calls

  | `--count` | lock (ms) | total (ms) | saving |
  |--:|--:|--:|--:|
  | 10 | 0.2230 | 0.2510 | 11% |
  | 100 | 2.5150 | 2.8690 | 12% |
  | 1000 | 20.0320 | 23.3490 | 14% |
  | 10000 | 105.2070 | 125.5310 | 16% |

Tree-SHA512: ebedfeeb4c8ad75c89128e53cae976a82967dbb5ffd129da0f7204ccf9c3c15070b3d509f3767bebd745512e410200cc546147c836e82409f95fc9b8d14fc3ed

Author: MarcoFalke

src/wallet/rpcwallet.cpp

@@ -1794,8 +1794,6 @@ UniValue listtransactions(const JSONRPCRequest& request)
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
-    LOCK2(cs_main, pwallet->cs_wallet);
-
     std::string strAccount = "*";
     if (!request.params[0].isNull())
         strAccount = request.params[0].get_str();
@@ -1817,20 +1815,25 @@ UniValue listtransactions(const JSONRPCRequest& request)
 
     UniValue ret(UniValue::VARR);
 
-    const CWallet::TxItems & txOrdered = pwallet->wtxOrdered;
-
-    // iterate backwards until we have nCount items to return:
-    for (CWallet::TxItems::const_reverse_iterator it = txOrdered.rbegin(); it != txOrdered.rend(); ++it)
     {
-        CWalletTx *const pwtx = (*it).second.first;
-        if (pwtx != nullptr)
-            ListTransactions(pwallet, *pwtx, strAccount, 0, true, ret, filter);
-        CAccountingEntry *const pacentry = (*it).second.second;
-        if (pacentry != nullptr)
-            AcentryToJSON(*pacentry, strAccount, ret);
+        LOCK2(cs_main, pwallet->cs_wallet);
+
+        const CWallet::TxItems & txOrdered = pwallet->wtxOrdered;
 
-        if ((int)ret.size() >= (nCount+nFrom)) break;
+        // iterate backwards until we have nCount items to return:
+        for (CWallet::TxItems::const_reverse_iterator it = txOrdered.rbegin(); it != txOrdered.rend(); ++it)
+        {
+            CWalletTx *const pwtx = (*it).second.first;
+            if (pwtx != nullptr)
+                ListTransactions(pwallet, *pwtx, strAccount, 0, true, ret, filter);
+            CAccountingEntry *const pacentry = (*it).second.second;
+            if (pacentry != nullptr)
+                AcentryToJSON(*pacentry, strAccount, ret);
+
+            if ((int)ret.size() >= (nCount+nFrom)) break;
+        }
     }
+
     // ret is newest to oldest
 
     if (nFrom > (int)ret.size())