Acquire cs_main lock before cs_wallet during wallet initialization

CWallet::MarkConflicted may acquire the cs_main lock after
CWalletDB::LoadWallet acquires the cs_wallet lock during wallet initialization.
(CWalletDB::LoadWallet calls ReadKeyValue which calls CWallet::LoadToWallet
which calls CWallet::MarkConflicted). This is the opposite order that cs_main
and cs_wallet locks are acquired in the rest of the code, and so leads to
POTENTIAL DEADLOCK DETECTED errors if bitcoin is built with -DDEBUG_LOCKORDER.

This commit changes CWallet::LoadWallet (which calls CWalletDB::LoadWallet) to
acquire both locks in the standard order. It also fixes some tests that were
acquiring wallet and main locks out of order and failed with the new locking in
CWallet::LoadWallet.

Error was reported by Luke Dashjr <luke-jr@utopios.org> in
https://botbot.me/freenode/bitcoin-core-dev/msg/90244330/

Github-Pull: #11126
Rebased-From: de9a1db2ed14e0c75ffd82dc031f7ad30c56d195

1 files changed, 2 insertions, 1 deletions

diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 318c159cfb..bf8981e4e8 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -3101,13 +3101,14 @@ CAmount CWallet::GetMinimumFee(unsigned int nTxBytes, const CCoinControl& coin_c
 
 DBErrors CWallet::LoadWallet(bool& fFirstRunRet)
 {
+    LOCK2(cs_main, cs_wallet);
+
     fFirstRunRet = false;
     DBErrors nLoadWalletRet = CWalletDB(*dbw,"cr+").LoadWallet(this);
     if (nLoadWalletRet == DB_NEED_REWRITE)
     {
         if (dbw->Rewrite("\x04pool"))
         {
-            LOCK(cs_wallet);
             setInternalKeyPool.clear();
             setExternalKeyPool.clear();
             m_pool_key_to_index.clear();