[Mono-list] Thread.Sleep --- bug or feature ?

[Yury Serdyuk]

Hi !
I have found strange behave of the "Sleep" constuct in (multi-threaded) 
programs, which use some libraries (dll's).

Concretely, my program launches some thread, which  makes some 
computations  and  uses Mono.Math.BigInteger class.
It write results to some array of integers.
Simultaneously, main thread traverses this array and falls to sleep if
the next value is "unready":

> using System;
> using Mono.Math;
> using System.Threading;
>
>
> public  class Mono_Sleep_Bug {
>
>  public static int M = 50;
>  public static bool contin = true;
>
>  public static int[] results;
>
>  public static void Main (  String[] args )  {
>
>   int i ;
>
>   int N = 2;
>   results = new int[M]  ;
>
>   for ( i=0;  i < M ; i++ )
>    results[ i ]  = 0;
>
>   ThreadStart tstart = new ThreadStart ( Worker );
>   ( new Thread ( tstart ) ).Start();
>
>   i = 0  ;
>
>   while ( i  < N  )
>   {
>    while ( results[i]  == 0   )
>    {
>     DateTime dt1 = DateTime.Now;
>     Thread.Sleep( 10  );
>     DateTime dt2 = DateTime.Now;
>     Console.WriteLine ( "Sleep time = " + (dt2-dt1).TotalSeconds );
>    }
>
>    i++  ;
>    Console.WriteLine( "*********i=" + i + "****************"  )  ;
>
>   }
>
>   contin  = false  ;
>  }
>
>   public static void Worker ()
>   {
>    BigInteger L;
>
>    BigInteger one = new BigInteger( (uint)1  )  ;
>
>    int q  = 0;
>
>    while ( q < M   )
>    { Console.WriteLine ( "q=" + q );
>      L  = one;
>
>      for ( int j  = 0; j  < 100000; j++   )
>        L = BigInteger.Add ( L, one );
>
>      results[ q ]  = 1;
>      q  = q + 1;
>
>    }
>
>   }
>
> }

While I use
Sleep ( 10 );
the process is awaked after 15 secs. !!!

> [serdyuk at skif ]$ mono Mono_Sleep_Bug.exe
> q=0
> Sleep time = 0.030861
> q=1
>             .   .   .
> q=48
> q=49
> Sleep time = 15.033854
> *********i=1****************
> *********i=2****************

 From the other side, it's all OK for the equivalent program with "long" 
integers in place of BigIntegers:

> using System;
> using Mono.Math;
> using System.Threading;
>
>
> public  class Mono_Sleep_Bug_long {
>
>  public static int M = 50;
>  public static bool contin = true;
>  
>  public static int[] results;
>
>  public static void Main (  String[] args )  {
>
>   int i ;
>
>   int N = 2;
>   results = new int[M]  ;
>
>   for ( i=0;  i < M ; i++ )
>    results[ i ]  = 0;
>
>   ThreadStart tstart = new ThreadStart ( Worker );
>   ( new Thread ( tstart ) ).Start();
>
>   i = 0  ;
>  
>   while ( i  < N  )
>   {
>    while ( results[i]  == 0   )
>    {
>     DateTime dt1 = DateTime.Now;
>     Thread.Sleep( 10  );
>     DateTime dt2 = DateTime.Now;
>     Console.WriteLine ( "Sleep time = " + (dt2-dt1).TotalSeconds );
>    }
>
>    i++  ;
>    Console.WriteLine( "*********i=" + i + "****************"  )  ;
>     
>   }
>
>   contin  = false  ;
>  }
>
>   public static void Worker ()
>   {
>    long L;
>    
>    long one = 1;
>
>    int q  = 0;
>    
>    while ( q < M   )
>    { Console.WriteLine ( "q=" + q );
>      L  = one;
>
>      for ( int j  = 0; j  < 1000000; j++   )   
>        L = L + one;
>        
>      results[ q ]  = 1;
>      q  = q + 1;         
>     
>    }
>
>   }
>  
> }

> [serdyuk at skif ]$ mono Mono_Sleep_Bug_long.exe
> q=0
> q=1
> Sleep time = 0.035377
> *********i=1****************
> q=2
> q=3
> Sleep time = 0.01327
> *********i=2****************
> q=4
>                 . .  .
>
> q=47
> q=48
> q=49

Some details about runs:
1) to compile Mono_Sleep_Bug
 >mcs /r:Mono.Security Mono_Sleep_Bug42.cs
2)  $ uname -a
Linux skif 2.4.27 #1 SMP Thu Apr 14 15:25:11 MSD 2005 i686 athlon i386 
GNU/Linux
3) $ mono -V
Mono JIT compiler version 1.2.5.2 (tarball)
Copyright (C) 2002-2007 Novell, Inc and Contributors. www.mono-project.com
        TLS:           __thread
        GC:            Included Boehm (with typed GC)
        SIGSEGV:       normal
        Architecture:  x86
        Disabled:      none

Moreover, this effect is occured using arbitrary library ( for big numbers).
In particularly, at first I have faced with this problem trying to use
Oyster.IntX.dll 
(http://contest2005.gotdotnet.ru/Request/Tools/UtilitiesLib/Downloads_GetFile.aspx?id=169728).

But under Windows it's OK (in particularly, with Oyster.IntX.dll).

Please, help.

Best wishes,
                     Yury Serdyuk.

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