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PONhibernate: Why does this cause a deadlock?
 

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  1. PONhibernate: Why does this cause a deadlock?
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    <p>I only have a single resource that SQL Server should be locking which is the Company table but the following console application is deadlocking. Why?</p> <pre><code>using System; using System.Collections.Generic; using System.Data; using System.Diagnostics; using System.Linq; using System.Text; using System.Threading.Tasks; using DataAccess; using NHibernate; using NHibernate.Cfg; using NHibernate.Context; using NHibernate.Tool.hbm2ddl; namespace NhibernatePlayground { class Program { private static ISessionFactory _sessionFactory; private static Configuration _configuration; private static int TotalThreadCount = 20; private static int LoopCount = 1000; private static void Main(string[] args) { //App_Start.NHibernateProfilerBootstrapper.PreStart(); _configuration = BuildConfiguration(); var se = new SchemaExport(_configuration); se.Create(false, true); _sessionFactory = _configuration.BuildSessionFactory(); int companyId = Seed(); Stopwatch sw = new Stopwatch(); sw.Start(); Task[] tasks = new Task[TotalThreadCount]; for (int i = 0; i &lt; TotalThreadCount; i ++) { tasks[i] = Task.Factory.StartNew(() =&gt; IncreaseEmployeeCount(LoopCount, companyId)); } //Block until all tasks complete. Task.WaitAll(tasks); sw.Stop(); Console.WriteLine("Employee Count: " + GetEmployeeCount(companyId)); Console.WriteLine("Total Milliseconds: " + sw.ElapsedMilliseconds); Console.ReadKey(); } private static Configuration BuildConfiguration() { Configuration configuration = new Configuration(); configuration.Configure(); // A configuration.AddAssembly(typeof(Company).Assembly); // B return configuration; } private static void IncreaseEmployeeCount(int count, int companyId) { for (int i = 0; i &lt; count; i++) { using (ISession _session = _sessionFactory.OpenSession()) { using (ITransaction _transaction = _session.BeginTransaction(IsolationLevel.Serializable)) { var company = _session.Get&lt;Company&gt;(companyId); company.EmployeeCount++; _session.Save(company); _transaction.Commit(); } } } } private static int Seed() { using (ISession _session = _sessionFactory.OpenSession()) { using (ITransaction _transaction = _session.BeginTransaction()) { Company company = new Company { CompanyName = "Angus" }; _session.Save(company); _transaction.Commit(); return company.Id; } } } private static int GetEmployeeCount(int companyId) { using (ISession _session = _sessionFactory.OpenSession()) { using (ITransaction _transaction = _session.BeginTransaction()) { Company company = _session.Get&lt;Company&gt;(companyId); return company.EmployeeCount; } } } } } </code></pre>
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    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USburnt1ce
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      1. LTLinked
    1. PL
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      1. LTLinked
    1. This table or related slice is empty.
    1. This table or related slice is empty.
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      1. PONhibernate: Why does this cause a deadlock?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COUse SQL Server Profiler to get what's happening at database level. You'll then get the deadlock graph.
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      1. PONhibernate: Why does this cause a deadlock?
      1. USMLeblanc
    2. COCalling Save() on an object already known by the session is useless.
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      1. PONhibernate: Why does this cause a deadlock?
      1. USOskar Berggren
    3. COThere are multiple types of locks. It also depends on transaction isolation level, which also depends on database settings. I would investigate if multiple read locks are being taken, preventing anyone from also acquiring the required write lock.
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      1. PONhibernate: Why does this cause a deadlock?
      1. USOskar Berggren
 

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