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！
}
            if (!destinations.insert(dest).second) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, std::string("Invalid parameter, duplicated address: ") + input.get_str());
            }
        }
    }
    bool include_unsafe = true;
    if (!request.params[3].isNull()) {
        RPCTypeCheckArgument(request.params[3], UniValue::VBOOL);
        include_unsafe = request.params[3].get_bool();
    }
    CAmount nMinimumAmount = 0;
    CAmount nMaximumAmount = MAX_MONEY;
    CAmount nMinimumSumAmount = MAX_MONEY;
    uint64_t nMaximumCount = 0;
    if (!request.params[4].isNull()) {
        const UniValue& options = request.params[4].get_obj();
        if (options.exists("minimumAmount"))
            nMinimumAmount = AmountFromValue(options["minimumAmount"]);
        if (options.exists("maximumAmount"))
            nMaximumAmount = AmountFromValue(options["maximumAmount"]);
        if (options.exists("minimumSumAmount"))
            nMinimumSumAmount = AmountFromValue(options["minimumSumAmount"]);
        if (options.exists("maximumCount"))
            nMaximumCount = options["maximumCount"].get_int64();
    }
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    UniValue results(UniValue::VARR);