[Mono-bugs] [Bug 668696] New: [Regression] SynchronizationLockException when accessing HttpApplicationState after Lock() is called

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https://bugzilla.novell.com/show_bug.cgi?id=668696

https://bugzilla.novell.com/show_bug.cgi?id=668696#c0


           Summary: [Regression] SynchronizationLockException when
                    accessing HttpApplicationState after Lock() is called
    Classification: Mono
           Product: Mono: Class Libraries
           Version: SVN
          Platform: Macintosh
        OS/Version: Mac OS X 10.6
            Status: NEW
          Severity: Major
          Priority: P5 - None
         Component: Sys.Web
        AssignedTo: mhabersack at novell.com
        ReportedBy: curtis.wensley at gmail.com
         QAContact: mono-bugs at lists.ximian.com
          Found By: ---
           Blocker: ---


Created an attachment (id=411590)
 --> (http://bugzilla.novell.com/attachment.cgi?id=411590)
Sample to reproduce the error

Description of Problem:
When using Lock()/Unlock() to access/add elements to the HttpApplicationState
(HttpContext.Current.Application) to deal with threading issues, a
System.Threading.SynchronizationLockException is thrown.

The pattern used to add to the application state in an IHttpModule is:
    const string MyKey = "mykey";
    var app = HttpContext.Current.Application;
    if (app[MyKey] == null)
    {
        app.Lock();
        if (app[MyKey] == null)  // exception here
        {
            app[MyKey] = "some object"; 
        }
        app.UnLock();
    }

Steps to reproduce the problem:
1. Compile & run attached application


Actual Results:
a SynchronizationLockException is thrown

Expected Results:
Should not throw an exception

How often does this happen? 
Every time

Additional Information:
Stack Trace:
System.Threading.SynchronizationLockException: The current thread has not
entered the lock in read mode
  at System.Threading.ReaderWriterLockSlim.ExitReadLock () [0x00022] in
/private/tmp/monobuild/build/BUILD/mono-2.10/mcs/class/System.Core/System.Threading/ReaderWriterLockSlim.cs:211 
  at System.Web.HttpApplicationState.Get (System.String name) [0x0001a] in
/private/tmp/monobuild/build/BUILD/mono-2.10/mcs/class/System.Web/System.Web/HttpApplicationState.cs:84 
  at System.Web.HttpApplicationState.get_Item (System.String name) [0x00000] in
/private/tmp/monobuild/build/BUILD/mono-2.10/mcs/class/System.Web/System.Web/HttpApplicationState.cs:182 
  at TestCustomAppModule.MyModule.HandleContextBeginRequest (System.Object
sender, System.EventArgs e) [0x0000b] in
/Users/cwensley/Projects/test/TestCustomAppModule/TestCustomAppModule/MyModule.cs:22 
  at System.Web.HttpApplication+<RunHooks>c__Iterator5.MoveNext () [0x001aa] in
/private/tmp/monobuild/build/BUILD/mono-2.10/mcs/class/System.Web/System.Web/HttpApplication.cs:1038 
  at System.Web.HttpApplication+<Pipeline>c__Iterator6.MoveNext () [0x00137] in
/private/tmp/monobuild/build/BUILD/mono-2.10/mcs/class/System.Web/System.Web/HttpApplication.cs:1198 
  at System.Web.HttpApplication.Tick () [0x00000] in
/private/tmp/monobuild/build/BUILD/mono-2.10/mcs/class/System.Web/System.Web/HttpApplication.cs:926

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