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！
const TransactionError err = pwallet->FillPSBT(psbtx, complete, 1, false, bip32derivs);
    if (err != TransactionError::OK) {
        throw JSONRPCTransactionError(err);
    }
    
    CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
    ssTx << psbtx;
    UniValue result(UniValue::VOBJ);
    result.pushKV("psbt", EncodeBase64(ssTx.str()));
    result.pushKV("fee", ValueFromAmount(fee));
    result.pushKV("changepos", change_position);
    return result;
}
UniValue abortrescan(const JSONRPCRequest& request); 
UniValue dumpprivkey(const JSONRPCRequest& request); 
UniValue importprivkey(const JSONRPCRequest& request);
UniValue importaddress(const JSONRPCRequest& request);
UniValue importpubkey(const JSONRPCRequest& request);
UniValue dumpwallet(const JSONRPCRequest& request);
UniValue importwallet(const JSONRPCRequest& request);
UniValue importprunedfunds(const JSONRPCRequest& request);
UniValue removeprunedfunds(const JSONRPCRequest& request);
UniValue importmulti(const JSONRPCRequest& request);
static const CRPCCommand commands[] =
{ 
    
    { "rawtransactions",    "fundrawtransaction",               &fundrawtransaction,            {"hexstring","options","iswitness"} },
    { "wallet",             "abandontransaction",               &abandontransaction,            {"txid"} },
    { "wallet",             "abortrescan",                      &abortrescan,                   {} },
    { "wallet",             "addmultisigaddress",               &addmultisigaddress,            {"nrequired","keys","label","address_type"} },