Question

I have a server which handles multiple incoming socket connections and creates 2 different threads which store the data in XML format.

I was using the lock statement for thread safety almost in every event handler called asyncronously and in the 2 threads in different parts of code. Sadly using this approach my application significantly slows down.

I tried to not use lock at all and the server is very fast in execution, even the file storage seems to boost; but the program crashes for reasons I don’t understand after 30sec – 1min. of work.

So. I thought that the best way is to use less locks or to use it only there where’s strictly necessary. As such, I have 2 questions:

1. Is the lock needed when I write to the public accessed variables (C# lists) only or even when I read from them ?

2. Is the lock needed only in the asyncronous threads created by the socket handler or in other places too ?

Someone could give me some practical guidelines, about how to operate. I’ll not post the whole code this time. It hasn’t sense to post about 2500 lines of code.

Answer 1

Is the lock needed when I write to the public accessed variables (C# lists) only or even when I read from them ?

Yes (even when you read).

Is the lock needed only in the asyncronous threads created by the socket handler or in other places too ?

Yes. Wherever code accesses a section of code which is shared, always lock.

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This sounds like you may not be locking individual objects, but locking one thing for all lock situations.

If so put in smart discrete locks by creating individual unique objects which relate and lock only certain sections at a time, which don’t interfere with other threads in other sections.

Here is an example:

// This class simulates the use of two different thread safe resources and how to lock them
// for thread safety but not block other threads getting different resources.
public class SmartLocking
{
    private string StrResource1 { get; set; }
    private string StrResource2 { get; set; }

    private object _Lock1 = new object();
    private object _Lock2 = new object();

    public void DoWorkOn1( string change )
    {
        lock (_Lock1)
        {
            _Resource1 = change;
        }
    }

    public void DoWorkOn2( string change2 )
    {
        lock (_Lock2)
        {
            _Resource2 = change2;
        }
    }
}