Waiting for some time until a condition is met

Question

5.00/5 (1 vote)

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I have a code like this which executes in a different thread than main thread.

C#

if(_isSTminStarted && (_stMinExpired == false))
            {
                //wait till stMin is expired
                String message = string.Empty;
                do
                {
                    message = "Waiting till STmin expires " + DateTime.Now.ToString("h:mm:ss.fff");
                    _logger.Info(message);
                    

                } while (_stMinExpired == false);               
           
                _isSTminStarted = true;
                _timer.STminTimerStarted(_stMinRecieved);

                CanFrame consecutiveFrame = _fragmentedFrameQueue.Dequeue();
                PublishFrame(consecutiveFrame);
            }

Please see the do while loop , i have added that because i have to wait until a timer expires and _stMinExpired is set to true. Then only i should send next frame.

This flag is set when a System.threading.timer expires. But i don't think this is the ideal way to wait till that time. can you suggest some ways in which i can wait in this thread till that flag is set rather than putting do while loop.

Posted 10-Aug-11 22:27pm

glued-to-code

Updated 12-May-17 7:39am

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walterhevedeich 11-Aug-11 4:35am

I don't see any problem doing this, unless you don't want to log the message multiple times until _stMinExpired has been set to true.

3 solutions

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Firo Atrum Ventus · Accepted Answer · 2011-08-10T22:54:00

Solution 2

Try using AutoResetEvent[^].

Posted 10-Aug-11 22:54pm

Firo Atrum Ventus

Comments

glued-to-code 11-Aug-11 5:14am

Yes this seems good, i can give it a try.

BobJanova 11-Aug-11 5:39am

Correct approach, 5.

glued-to-code 11-Aug-11 5:48am

Hi, Thanks Bob and Firo... This was exactly what i wanted and i have used it and is working as i expected. Thanks again.

BobJanova · Accepted Answer · 2011-08-10T23:45:00

As Firo mentions, you want to use one of the event based wait handlers (AutoResetEvent or ManualResetEvent) for this. They are designed for exactly what you ask here: waiting until something happens in another thread at an unknown time.

class Test {
  AutoResetEvent waitHandle = new AutoResetEvent(false);

 void SpawnThread(){
  Thread t = new Thread(ThreadMethod);
  t.Start();
 }
 
 void ThreadMethod(){
  waitHandle.WaitOne();
  CanFrame consecutiveFrame = _fragmentedFrameQueue.Dequeue();
  PublishFrame(consecutiveFrame);
 }

 void SomeLongOtherMethod(){
  DoStuffThatTakesAWhile();
  waitHandle.Set(); // This will release the thread.
 }
}

You should never wait by using a tight loop. That will run a core at 100% CPU and make your app unpopular. Wait handles, and Thread.Sleep as well, are OS level triggers and put your thread into a non-running state that doesn't use CPU time.

OriginalGriff · Accepted Answer · 2011-08-10T22:33:00

Solution 1

Use Thread.Sleep[^] instead - it can wait for a specific time before your task does anything else.

Posted 10-Aug-11 22:33pm

OriginalGriff

Comments

glued-to-code 11-Aug-11 4:37am

But i don't have specific time until which i should put sleep. When the timer expires , i have to proceed further in the code. So in that case i can't put a sleep for specific time because a case can come where i neednot wait if timer has already expired.

OriginalGriff 11-Aug-11 5:08am

So instead sleep for 100ms, and check again, or kill your task and re-start it when the timer expires.

BobJanova 11-Aug-11 5:40am

This would work, but reset events are better if they can be used instead.

glued-to-code 11-Aug-11 5:49am

Thanks to both of you. i think Bob is right.

Waiting for some time until a condition is met

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Waiting for some time until a condition is met

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