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！
}
        }
    }
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    auto locked_chain = pwallet->chain().lock();
    LOCK(pwallet->cs_wallet);
    EnsureWalletIsUnlocked(pwallet);
    std::vector<std::string> errors;
    CAmount old_fee;
    CAmount new_fee;
    CMutableTransaction mtx;
    feebumper::Result res;
    
    res = feebumper::CreateRateBumpTransaction(*pwallet, hash, coin_control, errors, old_fee, new_fee, mtx);
    if (res != feebumper::Result::OK) {
        switch(res) {
            case feebumper::Result::INVALID_ADDRESS_OR_KEY:
                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, errors[0]);
                break;
            case feebumper::Result::INVALID_REQUEST:
                throw JSONRPCError(RPC_INVALID_REQUEST, errors[0]);
                break;
            case feebumper::Result::INVALID_PARAMETER:
                throw JSONRPCError(RPC_INVALID_PARAMETER, errors[0]);
                break;
            case feebumper::Result::WALLET_ERROR:
                throw JSONRPCError(RPC_WALLET_ERROR, errors[0]);
                break;