Critical Section unmanaged C++ not working

Question

3.00/5 (2 votes)

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I have some code in a C++ CLR program with the below Critical Section code.

C#

<pre lang="xml">
///Test.cpp
static CRITICAL_SECTION	PrintCriticalSection;
void Test(int sleep1,int threadNumber)
    {
        cout&lt;&lt;&quot;Thread &quot;&lt;&lt;threadNumber&lt;&lt;&quot; Starts. Sleeping for &quot;&lt;&lt;sleep1&lt;&lt;&quot; seconds.\n&quot;;
        EnterCriticalSection(&amp;PrintCriticalSection);
        Sleep(sleep1);
        LeaveCriticalSection(&amp;PrintCriticalSection);
        cout&lt;&lt;&quot;Thread &quot;&lt;&lt;threadNumber&lt;&lt;&quot; Ends.\n&quot;;

    }</pre>

I am calling this code using 2 Threads

C#

<pre lang="xml">
class Program
    {
         Thread thread1;
         Thread thread2;
         PhoneCLR.PhonePortCLR test1;
         PhoneCLR.PhonePortCLR test2;
        static void Main(string[] args)
        {
            Program program1=new Program();
            program1.Test1();
             }

        void Test1()
        {
            test1 = new PhonePortCLR(1, 1, 1, 1, true, false, true, false, 1);
            test2 = new PhonePortCLR(1, 1, 1, 1, true, false, true, false, 1);
            PhonePortCLR.InitGlobalOnce(1, false, false, false, false);
            thread1 = new Thread(new ThreadStart(function1));
            thread2 = new Thread(new ThreadStart(function2));
            thread1.Start();
            thread2.Start();
           
            Console.ReadLine();
        }
       
         void function1()
        {
            test1.Test(10000, 1);
        }
         void function2()
        {
            test2.Test(100,2);
        }
    }
}
</pre>

The output in console window is supposed to be :

Thread 2 Starts. Sleeping for 100 seconds.
Thread 1 Starts. Sleeping for 10000 seconds.
///There is supposed to be a pause of 10,000 seconds here
Thread 2 Ends.
Thread 1 Ends.

But the output I am getting is random. Sometimes I get the above but sometimes I get below Output. It is so weird. Why is this the case? What can I use instead to fix this issue? Help!!!!! Its like 1 in 6 times I get below output. I am glad I caught this. I also notice that if I make the variable global instead of static, I get the below every time( Critical Section does not work)

The output in console window is sometimes:

Thread 2 Starts. Sleeping for 100 seconds.
Thread 1 Starts. Sleeping for 10000 seconds.
Thread 2 Ends.
///The 10 second pause happens now here...
Thread 1 Ends.

Posted 22-Jan-13 17:44pm

jobin007007

Updated 22-Jan-13 17:50pm

v2

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Comments

Sergey Alexandrovich Kryukov 23-Jan-13 0:09am

Please let me inform you that you've committed a serious abuse. Each and every of your "answers" in this forum is an abuse of different degree. All such "answers" are fake. Most of them are other questions. Worse, some of them you accepted by yourself, which can be qualified as cheating.

Is there anything you are going to do with that?
—SA

[no name] 23-Jan-13 0:44am

I am not sure what you mean . You are talking about this thread?

2 solutions

Solution 1

This is exactly the expected result.

You misuse CriticalSection in such a funny way which I never even imagined. What do you "protect" with it? The call to Sleep!

Case closed.

I cannot imagine the way you could possibly think. Unless this is a slip of a hand, I would say you have no idea what CriticalSection is used for. Try to understand it. For this purpose, read this: http://en.wikipedia.org/wiki/Mutual_exclusion[^].

Better now? :-)

—SA

Posted 22-Jan-13 17:57pm

Sergey Alexandrovich Kryukov

Updated 22-Jan-13 17:59pm

v3

Comments

[no name] 23-Jan-13 0:01am

This is merely test code i wrote to prove that Thread 2 is able to get past Thread1. I want Thread 2 to not execute when it is entering Critical sections. I guess you have to follow the examples a little bit more. Does that make it more clear?

Sergey Alexandrovich Kryukov 23-Jan-13 0:05am

Please tell me: do you sandwich Speep with critical section calls or not? I can see it right now.
—SA

[no name] 23-Jan-13 0:09am

Yes I put a sleep there depending on the thread. The sleep is there to identify that Thread 2 is not able to get past the sleep time of Thread 1 and gives me visual confirmation.

Sergey Alexandrovich Kryukov 23-Jan-13 0:13am

OK, that settles the case. I understand the possible purpose of sleep, but your critical section does nothing. Look, I'm too lazy to describe the scenario showing the output you got. You can do it by yourself. In other words, you don't do any synchronization, substitute it with so called "race condition" (read about it) instead.
—SA

[no name] 23-Jan-13 0:21am

I think I found out why...See my comments. Is that what you mean?
Yes the sleep does nothing other than let me count that 10 seconds have elapsed and thread 2 is not outputting anything on the screen.

Kuthuparakkal 23-Jan-13 0:05am

good answer 5+

Sergey Alexandrovich Kryukov 23-Jan-13 0:07am

Thank you very much.

Please take a look at my comment to the question, above.
—SA

[no name] 23-Jan-13 0:18am

I might have found out the reason why I have the problem. When I start the 2 threads, there is no guarantee that Thread1 or Thread 2 will be starting first. I put the below to make sure that thread2 will always be starting first and this seemed to make sure that Thread 2 will not access the function Test critical section region if Thread2 is already there.
thread1.Start();
Thread.Sleep(1000);
thread2.Start();

Sergey Alexandrovich Kryukov 23-Jan-13 0:21am

Wrong. You are not using CriticalSection properly.

Here is the experiment to do: Move Enter to the very beginning of the Test method, Leave — to the very end. All your cases of "entangled" calls will disappear immediately, I'll guarantee that.

Got the hint?

—SA

Sergey Alexandrovich Kryukov 23-Jan-13 0:23am

And let me warn you: all your thinking is in the ways of "race condition", which produce stochastic behavior. Isn't it obvious? Unpredictable order of execution.

[no name] 23-Jan-13 0:24am

I think you might have to run the sample to understand. I might have made the example hard to follow.
Isn't the output correct if critical section is working?

Thread 2 Starts. Sleeping for 100 seconds.
Thread 1 Starts. Sleeping for 10000 seconds.
///There is supposed to be a pause of 10,000 seconds here
Thread 2 Ends.
Thread 1 Ends.

Sergey Alexandrovich Kryukov 23-Jan-13 0:26am

Who has problems, you or me? Did you do what I advised? No.
It's useless to help anyone who cannot listen.
You should do the experiment I just described above, only then we can continue discussion, OK?
—SA

[no name] 23-Jan-13 0:29am

Ok wow. You are right . that was an easier example to implement. I don't know why my test case was like that.

[no name] 23-Jan-13 0:30am

Thanks for answering.

Sergey Alexandrovich Kryukov 23-Jan-13 0:40am

I told you that I would guarantee that. :-)

OK, now you probably can get it.
Please, read the referenced article and just think a bit at this sample, I'm sure you will derive correct conclusion.

I think now you can accept the answer formally (green button), right?

—SA

[no name] 23-Jan-13 0:26am

Sorry as below after i put the sleep.

Thread 1 Starts. Sleeping for 10000 seconds.
Thread 2 Starts. Sleeping for 100 seconds.
///There is supposed to be a pause of 10,000 seconds here
Thread 2 Ends.
Thread 1 Ends

Sergey Alexandrovich Kryukov 25-Jan-13 14:41pm

Oh, I can see you did not accept this answer but instead added your own and, again, self-accepted it. Don't you think it's called cheating?
—SA

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jobin007007 · Accepted Answer · 2013-01-22T18:40:00

Fixed by moving critical section to top of the test code
and adding

C#

thread1.Start();
Thread.Sleep(1000);
thread2.Start();

C#

static CRITICAL_SECTION	PrintCriticalSection;
void Test(int sleep1,int threadNumber)
    {
         EnterCriticalSection(&PrintCriticalSection);
        cout<<"Thread "<<threadNumber<<" Starts. Sleeping for "<<sleep1<<" seconds.\n";
       
        Sleep(sleep1);
        
        cout<<"Thread "<<threadNumber<<" Ends.\n";
        LeaveCriticalSection(&PrintCriticalSection);
    }
 


class Program
    {
         Thread thread1;
         Thread thread2;
         PhoneCLR.PhonePortCLR test1;
         PhoneCLR.PhonePortCLR test2;
        static void Main(string[] args)
        {
            Program program1=new Program();
            program1.Test1();
             }
 
        void Test1()
        {
            test1 = new PhonePortCLR(1, 1, 1, 1, true, false, true, false, 1);
            test2 = new PhonePortCLR(1, 1, 1, 1, true, false, true, false, 1);
            PhonePortCLR.InitGlobalOnce(1, false, false, false, false);
            thread1 = new Thread(new ThreadStart(function1));
            thread2 = new Thread(new ThreadStart(function2));
            thread1.Start();
            Thread.Sleep(1000);
            thread2.Start();
           
            Console.ReadLine();
        }
       
         void function1()
        {
            test1.Test(10000, 1);
        }
         void function2()
        {
            test2.Test(100,2);
        }
    }
}