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！
#include <util/fees.h>
#include <util/message.h> 
#include <util/moneystr.h>
#include <util/string.h>
#include <util/system.h>
#include <util/url.h>
#include <util/vector.h>
#include <wallet/coincontrol.h>
#include <wallet/feebumper.h>
#include <wallet/rpcwallet.h>
#include <wallet/wallet.h>
#include <wallet/walletdb.h>
#include <wallet/walletutil.h>
#include <stdint.h>
#include <univalue.h>
static const std::string WALLET_ENDPOINT_BASE = "/wallet/";
static const std::string HELP_REQUIRING_PASSPHRASE{"\nRequires wallet passphrase to be set with walletpassphrase call if wallet is encrypted.\n"};
static inline bool GetAvoidReuseFlag(const CWallet* const pwallet, const UniValue& param) {
    bool can_avoid_reuse = pwallet->IsWalletFlagSet(WALLET_FLAG_AVOID_REUSE);
    bool avoid_reuse = param.isNull() ? can_avoid_reuse : param.get_bool();
    if (avoid_reuse && !can_avoid_reuse) {
        throw JSONRPCError(RPC_WALLET_ERROR, "wallet does not have the \"avoid reuse\" feature enabled");
    }
    return avoid_reuse;
}
/** Used by RPC commands that have an include_watchonly parameter.
 *  We default to true for watchonly wallets if include_watchonly isn't
 *  explicitly set.
 */
static bool ParseIncludeWatchonly(const UniValue& include_watchonly, const CWallet& pwallet)