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！
coin_control.fAllowWatchOnly = pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS);
    
    coin_control.m_signal_bip125_rbf = true;
    if (!request.params[1].isNull()) {
        UniValue options = request.params[1];
        RPCTypeCheckObj(options,
            {
                {"confTarget", UniValueType(UniValue::VNUM)},
                {"fee_rate", UniValueType(UniValue::VNUM)},
                {"replaceable", UniValueType(UniValue::VBOOL)},
                {"estimate_mode", UniValueType(UniValue::VSTR)},
            },
            true, true);
        if (options.exists("confTarget") && options.exists("fee_rate")) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "confTarget can't be set with fee_rate. Please provide either a confirmation target in blocks for automatic fee estimation, or an explicit fee rate.");
        } else if (options.exists("confTarget")) { 
            coin_control.m_confirm_target = ParseConfirmTarget(options["confTarget"], pwallet->chain().estimateMaxBlocks());
        } else if (options.exists("fee_rate")) {
            CFeeRate fee_rate(AmountFromValue(options["fee_rate"]));
            if (fee_rate <= CFeeRate(0)) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid fee_rate %s (must be greater than 0)", fee_rate.ToString()));
            }
            coin_control.m_feerate = fee_rate;
        }
        if (options.exists("replaceable")) {
            coin_control.m_signal_bip125_rbf = options["replaceable"].get_bool();
        }
        if (options.exists("estimate_mode")) {
            if (!FeeModeFromString(options["estimate_mode"].get_str(), coin_control.m_fee_mode)) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid estimate_mode parameter");