wglMakeCurrent returning ERROR_BUSY #2

[Unick]

I have same problem as in this topic(http://www.opengl.org/discussion_boa...208&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.

[Aleksandar]

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.

[Unick]

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

[Aleksandar]

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.

[Unick]

Thanks.

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.

[Aleksandar]

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.

[Unick]

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.