如何在不使用事务的情况下创建死锁？

Question

I create simple console application in C# to simulate deadlock error. I used two threads. Code:

class Program
    {
        static void Main(string[] args)
        {           
            Thread[] tt = new Thread[2];
            try
            {
                tt[0] = new Thread(queryAdo1);
                tt[0].Priority = ThreadPriority.Highest;
                tt[0].Start();

                tt[1] = new Thread(queryAdo2);
                tt[1].Priority = ThreadPriority.Highest;
                tt[1].Start();


            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
                Console.ReadLine();
            }

        }


        private static void queryAdo1()
        {
            try
            {
                SqlConnection con = new SqlConnection("data source=.; database=BazaTest; integrated security=SSPI");
                SqlCommand cmd = new SqlCommand("spTransaction1", con);
                cmd.CommandType = System.Data.CommandType.StoredProcedure;

                con.Open();
                cmd.ExecuteNonQuery();
                con.Close();

                 Console.WriteLine("Done Well 1");
            }
            catch (SqlException ex)
            {
                if (ex.Number == 1205)
                {
                    Console.WriteLine("DeadLock 1");
                    Console.ReadLine();
                }
            }
        }

        private static void queryAdo2()
        {
            try
            {
                SqlConnection con = new SqlConnection("data source=.; database=BazaTest; integrated security=SSPI");
                SqlCommand cmd = new SqlCommand("spTransaction2", con);
                cmd.CommandType = System.Data.CommandType.StoredProcedure;

                con.Open();
                cmd.ExecuteNonQuery();
                con.Close();
                 Console.WriteLine("Done Well 2");
            }
            catch (SqlException ex)
            {
                if (ex.Number == 1205)
                {
                    Console.WriteLine("DeadLock 2");
                    Console.ReadLine();
                }
            }
        }
    }

Stored procedures:

 Create table TableA
(
    Id int identity primary key,
    Name nvarchar(50)
)
Go

Insert into TableA values ('Mark')
Go

Create table TableB
(
    Id int identity primary key,
    Name nvarchar(50)
)
Go

Insert into TableB values ('Mary')
Go

 Create procedure spTransaction1
as
Begin
    Begin Tran
    Update TableA Set Name = 'Mark Transaction 1' where Id = 1
    Waitfor delay '00:00:05'
    Update TableB Set Name = 'Mary Transaction 1' where Id = 1
    Commit Transaction
End
 Create procedure spTransaction2
as
Begin
    Begin Tran
    Update TableB Set Name = 'Mark Transaction 2' where Id = 1
    Waitfor delay '00:00:05'
    Update TableA Set Name = 'Mary Transaction 2' where Id = 1
    Commit Transaction
End

When I run my code I get response in console like this:

Done well 1
Deadlock 2

and it works correctly. I tried to create deadlock without using transaction but now i have no more ideas. I tried to eliminate transaction command from stored procedures spTransaction1 and spTransaction2 and i create more Threads using loop but I didnt create deadlock as I expected.I don't have big experience in parallel programming so maybe I did something wrong.. Is there any possibility to create deadlock without using transaction? If yes please write some example. It will be great if you'll use my code to solve this case ;) Thank you!

Answer 1

Deadlocks are unresolvable conflicts for resources - A needs B, B needs A during a sequence of instructions. Without transactions you're just running a bunch of single instructions. They might fail (or complete) but they won't deadlock because there is no dependency between the bits.