Programming Forums > Application Development > C#

Jason Isom · Dec 19th, 2005, 12:55 PM

I was hoping I could get your example to run into synchronization issues, but it outputted 48,000 lines without any synchronization issues. I'm relatively new to threading, although I do understand the theory behind it. I imagine I couldn't get it to throw an exception is because the operations are so simple.

However, all you have to do is surround your critical sections with lock(this) and you'll be set. It just hides all the implementation details of managing your own binary mutexes so that you don't have to do it yourself.

I apologize in advance if you already found a solution.

(Toggle Plain Text)

class Program
{
    StreamWriter sw = new StreamWriter("test.txt");
    public void methodA()
    {
        while (true)
        {
            p();
        }
    }

    public void methodB()
    {
        while (true)
        {
            p();
        }
    }

    public void p()
    {
        lock (this)
        {
            try
            {
                sw.WriteLine(Thread.CurrentThread.Name);
                Console.WriteLine(Thread.CurrentThread.Name);
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.Write(ex.Message);
            }
        }
    }

    public void a()
    {
        Thread objThreadA = new Thread(new ThreadStart(methodA));
        objThreadA.Name = "A-Thread";
        objThreadA.Start();

        Thread objThreadB = new Thread(new ThreadStart(methodB));
        objThreadB.Name = "B-Thread";
        objThreadB.Start();
    }
    static void Main(string[] args)
    {
        Program p = new Program();
        p.a();
    }
}

para · Dec 19th, 2005, 1:02 PM

This may be a useful resource: http://msdn.microsoft.com/library/de...cpconMutex.asp

MBirchmeier · Dec 19th, 2005, 1:08 PM

Quote:

Originally Posted by Jason Isom

I was hoping I could get your example to run into synchronization issues, but it outputted 48,000 lines without any synchronization issues. I'm relatively new to threading, although I do understand the theory behind it. I imagine I couldn't get it to throw an exception is because the operations are so simple.

However, all you have to do is surround your critical sections with lock(this) and you'll be set. It just hides all the implementation details of managing your own binary mutexes so that you don't have to do it yourself.

I apologize in advance if you already found a solution.

By the way : Good first post.

This is a good solution. I generally prefer to use mutexes instead of locks, but only to gaurentee(sp?) that any other functions or derived functions using the 'lock' will honor the locking routine. The resulting code would be

(Toggle Plain Text)

    public void p()
    {
        someMutex.WaitOne();
        try
        {
            sw.WriteLine(Thread.CurrentThread.Name);
            Console.WriteLine(Thread.CurrentThread.Name);
        }
        catch (Exception ex)
        {
            System.Diagnostics.Debug.Write(ex.Message);
        }
        someMutex.ReleaseMutex();       
    }

this way if p is made a virtual function, and a class overrides it it can simply lock the 'someMutex' object and proceed normally.

-MBirchmeier

myName · Dec 21st, 2005, 7:59 PM

mutex is added to the method p(someMessage). Now in testing state.

(Toggle Plain Text)

public void methodA()
{
	while( true )
	{
		...
		p( someMessage );
		Thread.Sleep(1000);
	}
}
		
public void methodB()
{
	while( true )
	{
		...
		p( someMessage );

		Thread.Sleep(1000);
	}
}

public void p( string someMessage)
{
       mut = new Mutex();
       someMutex.WaitOne();
        try
        {
            //Process write someMessage to File
        }
        catch (Exception ex)
        {
            System.Diagnostics.Debug.Write(ex.Message);
        }
        someMutex.ReleaseMutex();       
}

public void a()
{
	Thread objThreadA = new Thread( new ThreadStart( methodA) );
	objThreadA.Start();

	Thread objThreadB = new Thread( new ThreadStart( methodB) );
	objThreadB.Start();
}

The Dark · Dec 21st, 2005, 8:36 PM

Quote:

Originally Posted by myName

mutex is added to the method p(someMessage). Now in testing state.

(Toggle Plain Text)

public void methodA()
{
	while( true )
	{
		...
		p( someMessage );
		Thread.Sleep(1000);
	}
}
		
public void methodB()
{
	while( true )
	{
		...
		p( someMessage );

		Thread.Sleep(1000);
	}
}

public void p( string someMessage)
{
       mut = new Mutex();
       someMutex.WaitOne();
        try
        {
            //Process write someMessage to File
        }
        catch (Exception ex)
        {
            System.Diagnostics.Debug.Write(ex.Message);
        }
        someMutex.ReleaseMutex();       
}

public void a()
{
	Thread objThreadA = new Thread( new ThreadStart( methodA) );
	objThreadA.Start();

	Thread objThreadB = new Thread( new ThreadStart( methodB) );
	objThreadB.Start();
}

What is this line doing in p()?

(Toggle Plain Text)

       mut = new Mutex();

It is creating a new mutex for each time you output an error, but then never using it. You should remove this line. I assume someMutex is declared and created elsewhere.

Dameon · Dec 21st, 2005, 8:40 PM

TheDark is right. You need to have a mutex called someMutex (note the use of someMutex.WaitOne and ReleaseMutex) as a member of the class. Not a local variable, a member of the class. The point of a mutex is for both threads to access the same one (only one thread would be able to touch the local one) so that WaitOne blocks until ReleaseMutex is called.

Animatronic · Dec 21st, 2005, 9:58 PM

There is a synchronised attribute in c# equivalent to Java's keyword:

(Toggle Plain Text)

[System.Runtime.CompilerServices.MethodImplAttribute(System.Runtime.CompilerServices.MethodImplOptions.Synchronized)]

(without the random spaces)

and is the same as doing a lock(this) around the entire conents of the method.

myName · Dec 22nd, 2005, 3:12 AM

I change to this.

(Toggle Plain Text)

private static Mutex mut;

public void p( string someMessage)
{
       if( someMutex == null )
            someMutex = new Mutex();

       someMutex.WaitOne();
        try
        {
            //Process write someMessage to File
        }
        catch (Exception ex)
        {
            System.Diagnostics.Debug.Write(ex.Message);
        }
        someMutex.ReleaseMutex();       
}

pistalwhipped · Jan 16th, 2006, 1:40 PM

Not sure if anyone touched on this but here goes.

I had the same "requirement" for an application at my company. Basically we needed a logging system that all classes could access at the same time. So what we did is create a class "Logging" and added a static reference to it. Check it out:

(Toggle Plain Text)

public class logging 
{
	static private logging 			fInstance	= null;
	protected	string				fLogDirectory;
	protected	int					fDebugLevel;

	static public logging Instance() 
	{
		if( fInstance == null ) 
		{
			fInstance	= new logging();
		}
			return fInstance;
	}

	public	logging() 
	{
	        try 
		{
			fDebugLevel		= 1;
			fLogDirectory	= "c:/logs/";
		} 
		catch( Exception ) 
		{
			throw;
		}
	}
        public void Write( string text ) 
	{
		string fLogFileName;
		try 
		{
			DateTime	dt	= DateTime.Now;
			fLogFileName	= fLogDirectory + dt.ToString( "yyyy-MM-dd" ) + ".log";

			using( StreamWriter mLogFile = File.AppendText( fLogFileName ) ) 
			{
				mLogFile.WriteLine( text );
				mLogFile.Close();
			}

		} 
		catch( Exception ) {}
	}
}

to access the object just do the following:

logging fLog = logging.instance();

then call the Write() method. Pow! your done.

Jason Isom · Jan 16th, 2006, 1:57 PM

Quote:

Originally Posted by pistalwhipped

SNIP

You just used a very popular creational design pattern (maybe without realizing it?). It's called a Singleton class when you do what you're explaining, in case you wanted to research other design patterns.

I prefer to implement singletons with properties, but I guess that's just a style issue.

Dec 19th, 2005, 12:55 PM	#11
Jason Isom Programmer Join Date: Dec 2005 Posts: 53 Rep Power: 3	I was hoping I could get your example to run into synchronization issues, but it outputted 48,000 lines without any synchronization issues. I'm relatively new to threading, although I do understand the theory behind it. I imagine I couldn't get it to throw an exception is because the operations are so simple. However, all you have to do is surround your critical sections with lock(this) and you'll be set. It just hides all the implementation details of managing your own binary mutexes so that you don't have to do it yourself. I apologize in advance if you already found a solution. (Toggle Plain Text) class Program { StreamWriter sw = new StreamWriter("test.txt"); public void methodA() { while (true) { p(); } } public void methodB() { while (true) { p(); } } public void p() { lock (this) { try { sw.WriteLine(Thread.CurrentThread.Name); Console.WriteLine(Thread.CurrentThread.Name); } catch (Exception ex) { System.Diagnostics.Debug.Write(ex.Message); } } } public void a() { Thread objThreadA = new Thread(new ThreadStart(methodA)); objThreadA.Name = "A-Thread"; objThreadA.Start(); Thread objThreadB = new Thread(new ThreadStart(methodB)); objThreadB.Name = "B-Thread"; objThreadB.Start(); } static void Main(string[] args) { Program p = new Program(); p.a(); } } class Program { StreamWriter sw = new StreamWriter("test.txt"); public void methodA() { while (true) { p(); } } public void methodB() { while (true) { p(); } } public void p() { lock (this) { try { sw.WriteLine(Thread.CurrentThread.Name); Console.WriteLine(Thread.CurrentThread.Name); } catch (Exception ex) { System.Diagnostics.Debug.Write(ex.Message); } } } public void a() { Thread objThreadA = new Thread(new ThreadStart(methodA)); objThreadA.Name = "A-Thread"; objThreadA.Start(); Thread objThreadB = new Thread(new ThreadStart(methodB)); objThreadB.Name = "B-Thread"; objThreadB.Start(); } static void Main(string[] args) { Program p = new Program(); p.a(); } }

Dec 21st, 2005, 7:59 PM	#14
myName Programmer Join Date: Oct 2005 Posts: 48 Rep Power: 0	mutex is added to the method p(someMessage). Now in testing state. (Toggle Plain Text) public void methodA() { while( true ) { ... p( someMessage ); Thread.Sleep(1000); } } public void methodB() { while( true ) { ... p( someMessage ); Thread.Sleep(1000); } } public void p( string someMessage) { mut = new Mutex(); someMutex.WaitOne(); try { //Process write someMessage to File } catch (Exception ex) { System.Diagnostics.Debug.Write(ex.Message); } someMutex.ReleaseMutex(); } public void a() { Thread objThreadA = new Thread( new ThreadStart( methodA) ); objThreadA.Start(); Thread objThreadB = new Thread( new ThreadStart( methodB) ); objThreadB.Start(); } public void methodA() { while( true ) { ... p( someMessage ); Thread.Sleep(1000); } } public void methodB() { while( true ) { ... p( someMessage ); Thread.Sleep(1000); } } public void p( string someMessage) { mut = new Mutex(); someMutex.WaitOne(); try { //Process write someMessage to File } catch (Exception ex) { System.Diagnostics.Debug.Write(ex.Message); } someMutex.ReleaseMutex(); } public void a() { Thread objThreadA = new Thread( new ThreadStart( methodA) ); objThreadA.Start(); Thread objThreadB = new Thread( new ThreadStart( methodB) ); objThreadB.Start(); } Last edited by myName; Dec 21st, 2005 at 8:18 PM.

Dec 21st, 2005, 8:40 PM	#16
Dameon Troll Join Date: Apr 2005 Location: Texas Posts: 732 Rep Power: 4	TheDark is right. You need to have a mutex called someMutex (note the use of someMutex.WaitOne and ReleaseMutex) as a member of the class. Not a local variable, a member of the class. The point of a mutex is for both threads to access the same one (only one thread would be able to touch the local one) so that WaitOne blocks until ReleaseMutex is called. __________________ MD5(sig) = bcef75433db02e9ad9bf81d6f7c5c270

Dec 21st, 2005, 9:58 PM	#17
Animatronic Programmer Join Date: Jun 2005 Posts: 99 Rep Power: 4	There is a synchronised attribute in c# equivalent to Java's keyword: (Toggle Plain Text) [System.Runtime.CompilerServices.MethodImplAttribute(System.Runtime.CompilerServices.MethodImplOptions.Synchronized)] [System.Runtime.CompilerServices.MethodImplAttribute(System.Runtime.CompilerServices.MethodImplOptions.Synchronized)] (without the random spaces) and is the same as doing a lock(this) around the entire conents of the method.

Dec 22nd, 2005, 3:12 AM	#18
myName Programmer Join Date: Oct 2005 Posts: 48 Rep Power: 0	I change to this. (Toggle Plain Text) private static Mutex mut; public void p( string someMessage) { if( someMutex == null ) someMutex = new Mutex(); someMutex.WaitOne(); try { //Process write someMessage to File } catch (Exception ex) { System.Diagnostics.Debug.Write(ex.Message); } someMutex.ReleaseMutex(); } private static Mutex mut; public void p( string someMessage) { if( someMutex == null ) someMutex = new Mutex(); someMutex.WaitOne(); try { //Process write someMessage to File } catch (Exception ex) { System.Diagnostics.Debug.Write(ex.Message); } someMutex.ReleaseMutex(); } Last edited by myName; Dec 22nd, 2005 at 3:31 AM.

Dec 19th, 2005, 1:02 PM	#12
para Programmer Join Date: Dec 2005 Posts: 65 Rep Power: 3	This may be a useful resource: http://msdn.microsoft.com/library/de...cpconMutex.asp

Jan 16th, 2006, 1:40 PM	#19
pistalwhipped Newbie Join Date: Jan 2006 Posts: 3 Rep Power: 0	Not sure if anyone touched on this but here goes. I had the same "requirement" for an application at my company. Basically we needed a logging system that all classes could access at the same time. So what we did is create a class "Logging" and added a static reference to it. Check it out: (Toggle Plain Text) public class logging { static private logging fInstance = null; protected string fLogDirectory; protected int fDebugLevel; static public logging Instance() { if( fInstance == null ) { fInstance = new logging(); } return fInstance; } public logging() { try { fDebugLevel = 1; fLogDirectory = "c:/logs/"; } catch( Exception ) { throw; } } public void Write( string text ) { string fLogFileName; try { DateTime dt = DateTime.Now; fLogFileName = fLogDirectory + dt.ToString( "yyyy-MM-dd" ) + ".log"; using( StreamWriter mLogFile = File.AppendText( fLogFileName ) ) { mLogFile.WriteLine( text ); mLogFile.Close(); } } catch( Exception ) {} } } public class logging { static private logging fInstance = null; protected string fLogDirectory; protected int fDebugLevel; static public logging Instance() { if( fInstance == null ) { fInstance = new logging(); } return fInstance; } public logging() { try { fDebugLevel = 1; fLogDirectory = "c:/logs/"; } catch( Exception ) { throw; } } public void Write( string text ) { string fLogFileName; try { DateTime dt = DateTime.Now; fLogFileName = fLogDirectory + dt.ToString( "yyyy-MM-dd" ) + ".log"; using( StreamWriter mLogFile = File.AppendText( fLogFileName ) ) { mLogFile.WriteLine( text ); mLogFile.Close(); } } catch( Exception ) {} } } to access the object just do the following: logging fLog = logging.instance(); then call the Write() method. Pow! your done.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Programming Forums > Application Development > C#

2 Threads access a method in the same time.