Accessing a global variable from two separate threads

Question

I have a program that needs to access a global variable of type double from two different threads. Since it is just type double, do I still have to lock that code? I know this may not be the best programming practice, but for right now, this is what I am stuck with.

Thanks!!

Answer 1

Yes, using a lock would be wise.

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Mark the best replies as answers. "Fooling computers since 1971."

Answer 2

Reads of 4 bytes that are aligned are atomic.  Reads of unaligned bytes are not atomic.  And reads of 8 bytes (doubles) are not atomic.  So use a lock .

You are not stuck with anything...we can help you find options.  It's not that hard either.

class foo {
   private double n = 0.0;
 
   public void AddOne() {
      lock(this) {
         n += 1.0;
      }
   }
   public double Get() {
      lock(this) {
         return n;
      }
   }
}


If you feel your lock is inefficient, then let's discuss your algorithm.  Maybe you could offer a bit more of the details of your program and what you're trying to accomplish.

Answer 3

Yes, use a lock. But as you mentioned its a global (so static) variable, use it this way..

class yourClass
{
  yourFunction()
  {
     lock(typeof(ClassContainingStatic))           // or any class for that matter, so it will be a global lock   
     {
           your code;
      }
  }
}

Hope that helps..

Answer 4

The lock should be sufficient. If I run into more problems, I'll give a holler. Thanks for the input!!!