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！
},
                    {"replaceable", RPCArg::Type::BOOL,  "wallet default", "Allow this transaction to be replaced by a transaction with higher fees via BIP 125"},
                    {"conf_target", RPCArg::Type::NUM,  "wallet default", "Confirmation target (in blocks)"},
                    {"estimate_mode", RPCArg::Type::STR,  "UNSET", "The fee estimate mode, must be one of:\n"
            "       \"UNSET\"\n"
            "       \"ECONOMICAL\"\n"
            "       \"CONSERVATIVE\""},
                },
                 RPCResult{
                     RPCResult::Type::STR_HEX, "txid", "The transaction id for the send. Only 1 transaction is created regardless of\n"
            "the number of addresses."
                 },
                RPCExamples{
            "\nSend two amounts to two different addresses:\n"
            + HelpExampleCli("sendmany", "\"\" \"{\\\"" + EXAMPLE_ADDRESS[0] + "\\\":0.01,\\\"" + EXAMPLE_ADDRESS[1] + "\\\":0.02}\"") +
            "\nSend two amounts to two different addresses setting the confirmation and comment:\n"
            + HelpExampleCli("sendmany", "\"\" \"{\\\"" + EXAMPLE_ADDRESS[0] + "\\\":0.01,\\\"" + EXAMPLE_ADDRESS[1] + "\\\":0.02}\" 6 \"testing\"") +
            "\nSend two amounts to two different addresses, subtract fee from amount:\n"
            + HelpExampleCli("sendmany", "\"\" \"{\\\"" + EXAMPLE_ADDRESS[0] + "\\\":0.01,\\\"" + EXAMPLE_ADDRESS[1] + "\\\":0.02}\" 1 \"\" \"[\\\"" + EXAMPLE_ADDRESS[0] + "\\\",\\\"" + EXAMPLE_ADDRESS[1] + "\\\"]\"") +
            "\nAs a JSON-RPC call\n"
            + HelpExampleRpc("sendmany", "\"\", {\"" + EXAMPLE_ADDRESS[0] + "\":0.01,\"" + EXAMPLE_ADDRESS[1] + "\":0.02}, 6, \"testing\"")
                },
    }.Check(request);
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    auto locked_chain = pwallet->chain().lock();
    LOCK(pwallet->cs_wallet);
    if (!request.params[0].isNull() && !request.params[0].get_str().empty()) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Dummy value must be set to \"\"");