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！
}},
                        }},
                    }
                },
                RPCExamples{
                    HelpExampleCli("getaddressinfo", "\"" + EXAMPLE_ADDRESS[0] + "\"") +
                    HelpExampleRpc("getaddressinfo", "\"" + EXAMPLE_ADDRESS[0] + "\"")
                },
            }.Check(request);
    LOCK(pwallet->cs_wallet);
    UniValue ret(UniValue::VOBJ);
    CTxDestination dest = DecodeDestination(request.params[0].get_str());
    
    if (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid address");
    }
    std::string currentAddress = EncodeDestination(dest);
    ret.pushKV("address", currentAddress);
    CScript scriptPubKey = GetScriptForDestination(dest);
    ret.pushKV("scriptPubKey", HexStr(scriptPubKey.begin(), scriptPubKey.end()));
    std::unique_ptr<SigningProvider> provider = pwallet->GetSolvingProvider(scriptPubKey);
    isminetype mine = pwallet->IsMine(dest);
    ret.pushKV("ismine", bool(mine & ISMINE_SPENDABLE));
    bool solvable = provider && IsSolvable(*provider, scriptPubKey);
    ret.pushKV("solvable", solvable);
    if (solvable) {
       ret.pushKV("desc", InferDescriptor(scriptPubKey, *provider)->ToString());
    }
    ret.pushKV("iswatchonly", bool(mine & ISMINE_WATCH_ONLY));
    UniValue detail = DescribeWalletAddress(pwallet, dest);