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！
obj.pushKV("txcount",       (int)pwallet->mapWallet.size());
    obj.pushKV("keypoololdest", pwallet->GetOldestKeyPoolTime());
    obj.pushKV("keypoolsize", (int64_t)kpExternalSize);
    LegacyScriptPubKeyMan* spk_man = pwallet->GetLegacyScriptPubKeyMan();
    if (spk_man) {
        CKeyID seed_id = spk_man->GetHDChain().seed_id;
        if (!seed_id.IsNull()) {
            obj.pushKV("hdseedid", seed_id.GetHex());
        }
    }
    if (pwallet->CanSupportFeature(FEATURE_HD_SPLIT)) {
        obj.pushKV("keypoolsize_hd_internal",   (int64_t)(pwallet->GetKeyPoolSize() - kpExternalSize));
    }
    if (pwallet->IsCrypted()) {
        obj.pushKV("unlocked_until", pwallet->nRelockTime);
    }
    obj.pushKV("paytxfee", ValueFromAmount(pwallet->m_pay_tx_fee.GetFeePerK()));
    obj.pushKV("private_keys_enabled", !pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS));
    obj.pushKV("avoid_reuse", pwallet->IsWalletFlagSet(WALLET_FLAG_AVOID_REUSE));
    if (pwallet->IsScanning()) {
        UniValue scanning(UniValue::VOBJ);
        scanning.pushKV("duration", pwallet->ScanningDuration() / 1000);
        scanning.pushKV("progress", pwallet->ScanningProgress());
        obj.pushKV("scanning", scanning);
    } else {
        obj.pushKV("scanning", false);
    }
    return obj;
}
static UniValue listwalletdir(const JSONRPCRequest& request)