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！
{RPCResult::Type::NUM_TIME, "unlocked_until", "the " + UNIX_EPOCH_TIME + " until which the wallet is unlocked for transfers, or 0 if the wallet is locked"},
                        {RPCResult::Type::STR_AMOUNT, "paytxfee", "the transaction fee configuration, set in " + CURRENCY_UNIT + "/kB"},
                        {RPCResult::Type::STR_HEX, "hdseedid",  true, "the Hash160 of the HD seed (only present when HD is enabled)"},
                        {RPCResult::Type::BOOL, "private_keys_enabled", "false if privatekeys are disabled for this wallet (enforced watch-only wallet)"},
                        {RPCResult::Type::BOOL, "avoid_reuse", "whether this wallet tracks clean/dirty coins in terms of reuse"},
                        {RPCResult::Type::OBJ, "scanning", "current scanning details, or false if no scan is in progress",
                        {
                            {RPCResult::Type::NUM, "duration", "elapsed seconds since scan start"},
                            {RPCResult::Type::NUM, "progress", "scanning progress percentage [0.0, 1.0]"},
                        }},
                    }},
                },
                RPCExamples{
                    HelpExampleCli("getwalletinfo", "")
            + HelpExampleRpc("getwalletinfo", "")
                },
    }.Check(request);
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    auto locked_chain = pwallet->chain().lock();
    LOCK(pwallet->cs_wallet);
    UniValue obj(UniValue::VOBJ);
    size_t kpExternalSize = pwallet->KeypoolCountExternalKeys();
    const auto bal = pwallet->GetBalance();
    obj.pushKV("walletname", pwallet->GetName());
    obj.pushKV("walletversion", pwallet->GetVersion());
    obj.pushKV("balance", ValueFromAmount(bal.m_mine_trusted));
    obj.pushKV("unconfirmed_balance", ValueFromAmount(bal.m_mine_untrusted_pending));
    obj.pushKV("immature_balance", ValueFromAmount(bal.m_mine_immature));