Threads

[Jonas]

Hi

Well... i am trying to create a simple example on how to do syncronization
of threads using System.Threading.ReaderWriterLock.

As you probably know, you can read and write to the resource (critical section),
just aquiring a lock to it. My simple example, just have a class with 2 methods,
one to read and other to write. The main, when the programm stats, will loop
19 times and will create threads. According to the loop number, it will read
or write to the critical section.

Although, this is not working. I can read once (one thread). Then it writes
(another thread). But, the second time another thread tried to read, they
will read all...not "one by one". Although the writer lock is doing that.

Please see the code below and say somthing about. Thnks

Imports System.Threading
Module Module1

Sub Main()
Dim recurso As New CriticalSection() 'new instance of the class
Dim i As Integer

'loop and create threads
For i = 0 To 18

'if odds we will read the resource (critical section)
If i Mod 2 <> 0 Then
Dim threads As New Thread(AddressOf recurso.Read)
threads.Name = i
threads.Start()
Else 'otherwise, write
Dim threads2 As New Thread(AddressOf recurso.Write)
threads2.Name = i
threads2.Start()
End If
Next

End Sub

End Module

'this is the CRITICAL SECTION where the threads will try to read/write
Class CriticalSection

'object
Private rwLock As New ReaderWriterLock()

'to read the critical section
Public Sub Read()
rwLock.AcquireReaderLock(Timeout.Infinite)
Try
Console.WriteLine("LENDO o recurso com a thread " & Thread.CurrentThread.Name)
Thread.Sleep(5000)
Console.WriteLine("Fim da leitura...")
Finally

rwLock.ReleaseReaderLock()

End Try
End Sub

'to write to the CS
Public Sub Write()
rwLock.AcquireWriterLock(Timeout.Infinite)

Try
Console.WriteLine("ESCREVENDO no recurso com a thread " & Thread.CurrentThread.Name)
Thread.Sleep(2000)
Console.WriteLine("Fim da escrita...")
Finally
rwLock.ReleaseWriterLock()
End Try
End Sub

End Class

[Randy Charles Morin]

I posted an article in my semi-private community.
http://ca.msnusers.com/KBCafecom/art...56206591872755
Feedback would be nice.
Sorry, it's C#.
--
Randy Charles Morin
http://www.kbcafe.com

Feel free to contact me by private email or messenger
morin_randy@hotmail.com
randy@kbcafe.com

"Jonas" <asdas@mail.com> wrote in message news:3c6d78bd$1@10.1.10.29...
>
> Hi
>
> Well... i am trying to create a simple example on how to do syncronization
> of threads using System.Threading.ReaderWriterLock.
>
> As you probably know, you can read and write to the resource (critical section),
> just aquiring a lock to it. My simple example, just have a class with 2 methods,
> one to read and other to write. The main, when the programm stats, will loop
> 19 times and will create threads. According to the loop number, it will read
> or write to the critical section.
>
> Although, this is not working. I can read once (one thread). Then it writes
> (another thread). But, the second time another thread tried to read, they
> will read all...not "one by one". Although the writer lock is doing that.
>
> Please see the code below and say somthing about. Thnks
>
> Imports System.Threading
> Module Module1
>
> Sub Main()
> Dim recurso As New CriticalSection() 'new instance of the class
> Dim i As Integer
>
> 'loop and create threads
> For i = 0 To 18
>
> 'if odds we will read the resource (critical section)
> If i Mod 2 <> 0 Then
> Dim threads As New Thread(AddressOf recurso.Read)
> threads.Name = i
> threads.Start()
> Else 'otherwise, write
> Dim threads2 As New Thread(AddressOf recurso.Write)
> threads2.Name = i
> threads2.Start()
> End If
> Next
>
> End Sub
>
> End Module
>
> 'this is the CRITICAL SECTION where the threads will try to read/write
> Class CriticalSection
>
> 'object
> Private rwLock As New ReaderWriterLock()
>
> 'to read the critical section
> Public Sub Read()
> rwLock.AcquireReaderLock(Timeout.Infinite)
> Try
> Console.WriteLine("LENDO o recurso com a thread " & Thread.CurrentThread.Name)
> Thread.Sleep(5000)
> Console.WriteLine("Fim da leitura...")
> Finally
>
> rwLock.ReleaseReaderLock()
>
> End Try
> End Sub
>
> 'to write to the CS
> Public Sub Write()
> rwLock.AcquireWriterLock(Timeout.Infinite)
>
> Try
> Console.WriteLine("ESCREVENDO no recurso com a thread " & Thread.CurrentThread.Name)
> Thread.Sleep(2000)
> Console.WriteLine("Fim da escrita...")
> Finally
> rwLock.ReleaseWriterLock()
> End Try
> End Sub
>
> End Class

[Jonas]

Sorry dude.. when i tried to download the zip the browser showed a Forbidden
error.
Sorry.. but when i tryed to download the zip it gave me an error "Forbidden".

http://ca.msnusers.com/KBCafecom/Doc...reading.v3.zip

is this link right?

João Ferreira


"Randy Charles Morin" <rmorin@kbcafe.com> wrote:
>I posted an article in my semi-private community.
>http://ca.msnusers.com/KBCafecom/art...56206591872755
>Feedback would be nice.
>Sorry, it's C#.
>--
>Randy Charles Morin
>http://www.kbcafe.com
>
>Feel free to contact me by private email or messenger
>morin_randy@hotmail.com
>randy@kbcafe.com
>
>"Jonas" <asdas@mail.com> wrote in message news:3c6d78bd$1@10.1.10.29...
>>
>> Hi
>>
>> Well... i am trying to create a simple example on how to do syncronization
>> of threads using System.Threading.ReaderWriterLock.
>>
>> As you probably know, you can read and write to the resource (critical
section),
>> just aquiring a lock to it. My simple example, just have a class with
2 methods,
>> one to read and other to write. The main, when the programm stats, will
loop
>> 19 times and will create threads. According to the loop number, it will
read
>> or write to the critical section.
>>
>> Although, this is not working. I can read once (one thread). Then it writes
>> (another thread). But, the second time another thread tried to read, they
>> will read all...not "one by one". Although the writer lock is doing that.
>>
>> Please see the code below and say somthing about. Thnks
>>
>> Imports System.Threading
>> Module Module1
>>
>> Sub Main()
>> Dim recurso As New CriticalSection() 'new instance of the class
>> Dim i As Integer
>>
>> 'loop and create threads
>> For i = 0 To 18
>>
>> 'if odds we will read the resource (critical section)
>> If i Mod 2 <> 0 Then
>> Dim threads As New Thread(AddressOf recurso.Read)
>> threads.Name = i
>> threads.Start()
>> Else 'otherwise, write
>> Dim threads2 As New Thread(AddressOf recurso.Write)
>> threads2.Name = i
>> threads2.Start()
>> End If
>> Next
>>
>> End Sub
>>
>> End Module
>>
>> 'this is the CRITICAL SECTION where the threads will try to read/write
>> Class CriticalSection
>>
>> 'object
>> Private rwLock As New ReaderWriterLock()
>>
>> 'to read the critical section
>> Public Sub Read()
>> rwLock.AcquireReaderLock(Timeout.Infinite)
>> Try
>> Console.WriteLine("LENDO o recurso com a thread " & Thread.CurrentThread.Name)
>> Thread.Sleep(5000)
>> Console.WriteLine("Fim da leitura...")
>> Finally
>>
>> rwLock.ReleaseReaderLock()
>>
>> End Try
>> End Sub
>>
>> 'to write to the CS
>> Public Sub Write()
>> rwLock.AcquireWriterLock(Timeout.Infinite)
>>
>> Try
>> Console.WriteLine("ESCREVENDO no recurso com a thread " &
Thread.CurrentThread.Name)
>> Thread.Sleep(2000)
>> Console.WriteLine("Fim da escrita...")
>> Finally
>> rwLock.ReleaseWriterLock()
>> End Try
>> End Sub
>>
>> End Class
>
>