wglMakeCurrent returning ERROR_BUSY #2

I have same problem as in this topic(http://www.opengl.org/discussion_boards/ubbthreads.php?ubb=showflat&Number=196208&page=2)

I have different theads and each thread has different OpenGL context (each context has different Window (and DC)). These threads work simultaneously.

Each thread makes:

  1. Set current context.
  2. Make OpenGL operation.
  3. Set current context NULL.
  4. Any CPU work.
  5. Set current context.
  6. and so on.

Sometime very rarely I have ERROR_BUSY after wglMakeCurrent (I use getLastError).

I work under Windows.

If you’ve got separate contexts for each thread, you do not need to make them current on each draw call. Just once, at startup.
What you get is quite a normal behavior.

I must make SetCurrentContext for each rendering, because my component is used in big software system.

Then make your method to access rendering context that tries to get it untill succeedes. In other words, make a wrapper around MakeCurrent. That’s what I did long time ago to make it work properly with multithread access.


I tried this method. But if I tried MakeCurrent second time, it returned ok, but next call of MakeCurrent for this thread return ERROR_BUSY. It makes my component very slow.

I hope there is normal method for fix this problem.

A “normal” method would be using critical sections (or similar synchronization mechanism) to protect access to each context, or implementing all drawing in threads that own contexts and develop a mechanism to send them messages telling them what to draw.

Yes, critical sections are my current solution!

But I want to make multi-threaded render, I think it can be faster.

May be somebody knows the reason why this error occurs.