When i used the encrypted wallet to test transfer parallelly,i frequently got the trouble: The rpc server is not responding.My test script is like below:
#!/bin/sh
while [ 1 ]
do
./bitcoin-cli listaddressgroupings>null
./bitcoin-cli walletpassphrase "!@#$%^&*" 2
./bitcoin sendtoaddress "mhAW6mzs5DeCbzBUHXBi4U446Fdnr1z8U7" 0.01
done

When i open the dead lock trace macro and check the debug log,i found the last print is as below:
2018-12-17 08:27:58 ThreadRPCServer method=walletpassphrase
2018-12-17 08:27:58 LOCKCONTENTION: cs_main
2018-12-17 08:27:58 Locker: wallet/rpcwallet.cpp:2642
2018-12-17 08:27:58 LOCKCONTENTION: pWallet->cs_wallet
2018-12-17 08:27:58 Locker: wallet/rpcwallet.cpp:2607

The line no 2642 is walletpassphrase and 2607 is LockWallet. I checked the code,i found there is no log printed for this line in function "walletpassphrase":
"LogPrint(BCLog::RPC, "queue run of timer %s in %i seconds (using %s)\n", name, nSeconds, timerInterface->Name());" So i guess the reason may be:
When "walletpassphrase" is running and lock the cs_wallet,the last relock timer triggered and call "LockWallet"."LockWallet" want to lock the cs_wallet but it has been locked by "walletpassphrase",so "LockWallet" is blocked.When "walletpassphrase" run to call "RPCRunLater",the function will erase the timer from the std::map "deadlineTimers",but the timer's timeout call is blocked,so the dead lock take place.
Is my guess right?
How to reslove the issue?
Any help will be appreciative！
obj.pushKV("warning", Join(warnings, "\n"));
    return obj;
}
static UniValue unloadwallet(const JSONRPCRequest& request)
{
            RPCHelpMan{"unloadwallet",
                "Unloads the wallet referenced by the request endpoint otherwise unloads the wallet specified in the argument.\n"
                "Specifying the wallet name on a wallet endpoint is invalid.",
                {
                    {"wallet_name", RPCArg::Type::STR,  "the wallet name from the RPC request", "The name of the wallet to unload."},
                },
                RPCResult{RPCResult::Type::NONE, "", ""},
                RPCExamples{
                    HelpExampleCli("unloadwallet", "wallet_name")
            + HelpExampleRpc("unloadwallet", "wallet_name")
                },
            }.Check(request);
    std::string wallet_name;
    if (GetWalletNameFromJSONRPCRequest(request, wallet_name)) {
        if (!request.params[0].isNull()) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot unload the requested wallet");
        }
    } else {
        wallet_name = request.params[0].get_str();
    }
    std::shared_ptr<CWallet> wallet = GetWallet(wallet_name);
    if (!wallet) {
        throw JSONRPCError(RPC_WALLET_NOT_FOUND, "Requested wallet does not exist or is not loaded");
    }