rpc: Make unloadwallet wait for complete wallet unload

Github-Pull: #14941
Rebased-From: c37851d

src/init.cpp

@@ -286,6 +286,7 @@ void Shutdown(InitInterfaces& interfaces)
         LogPrintf("%s: Unable to remove PID file: %s\n", __func__, fsbridge::get_filesystem_error_message(e));
     }
     interfaces.chain_clients.clear();
+    g_wallet_init_interface.Close();
     UnregisterAllValidationInterfaces();
     GetMainSignals().UnregisterBackgroundSignalScheduler();
     GetMainSignals().UnregisterWithMempoolSignals(mempool);

src/wallet/init.cpp

@@ -135,4 +135,10 @@ void WalletInit::Construct(InitInterfaces& interfaces) const
     }
     gArgs.SoftSetArg("-wallet", "");
     interfaces.chain_clients.emplace_back(interfaces::MakeWalletClient(*interfaces.chain, gArgs.GetArgs("-wallet")));
+    auto wallets = GetWallets();
+    while (!wallets.empty()) {
+        auto wallet = wallets.back();
+        wallets.pop_back();
+        RemoveWallet(wallet);
+        UnloadWallet(std::move(wallet));
 }

src/wallet/wallet.cpp

@@ -125,6 +125,29 @@ static void ReleaseWallet(CWallet* wallet)
     g_wallet_release_cv.notify_all();
 }
 
+void UnloadWallet(std::shared_ptr<CWallet>&& wallet)
+{
+    // Mark wallet for unloading.
+    CWallet* pwallet = wallet.get();
+    {
+        std::lock_guard<std::mutex> lock(g_wallet_release_mutex);
+        auto it = g_unloading_wallet_set.insert(pwallet);
+        assert(it.second);
+    }
+    // The wallet can be in use so it's not possible to explicitly unload here.
+    // Notify the unload intent so that all remaining shared pointers are
+    // released.
+    pwallet->NotifyUnload();
+    // Time to ditch our shared_ptr and wait for ReleaseWallet call.
+    wallet.reset();
+    {
+        std::unique_lock<std::mutex> lock(g_wallet_release_mutex);
+        while (g_unloading_wallet_set.count(pwallet) == 1) {
+            g_wallet_release_cv.wait(lock);
+        }
+    }
+}
+
 void UnloadWallet(std::shared_ptr<CWallet>&& wallet)
 {
     // Mark wallet for unloading.