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！
{"estimate_mode", RPCArg::Type::STR,  "UNSET", "The fee estimate mode, must be one of:\n"
            "       \"UNSET\"\n"
            "       \"ECONOMICAL\"\n"
            "       \"CONSERVATIVE\""},
                    {"avoid_reuse", RPCArg::Type::BOOL,  "true", "(only available if avoid_reuse wallet flag is set) Avoid spending from dirty addresses; addresses are considered\n"
            "                             dirty if they have previously been used in a transaction."},
                },
                RPCResult{
                    RPCResult::Type::STR_HEX, "txid", "The transaction id."
                },
                RPCExamples{
                    HelpExampleCli("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\" 0.1")
            + HelpExampleCli("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\" 0.1 \"donation\" \"seans outpost\"")
            + HelpExampleCli("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\" 0.1 \"\" \"\" true")
            + HelpExampleRpc("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\", 0.1, \"donation\", \"seans outpost\"")
                },
            }.Check(request);
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    auto locked_chain = pwallet->chain().lock();
    LOCK(pwallet->cs_wallet);
    CTxDestination dest = DecodeDestination(request.params[0].get_str());
    if (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid address");
    }
    
    CAmount nAmount = AmountFromValue(request.params[1]);
    if (nAmount <= 0)
        throw JSONRPCError(RPC_TYPE_ERROR, "Invalid amount for send");