Uploading data to atlas texture in worker thread and sampling from same texture in render thread

Question

There are 2 OpenGLES2 contexts, that are is same "share group". I know that it's possible to upload texture in worker thread while it's not being used in render thread. But is it possible to upload portion of data to a region on atlas texture from worker thread and sample from same atlas texture (but from different region, of course)? I've read that rendering to a texture and sampling it will lead to undefined behavior (unless using NV_texture_fence), but it's not actually my case.

Answer 1

No, that breaks the 1st and 2nd rules from the docs:

It is your application’s responsibility to manage state changes to OpenGL ES objects when the sharegroup is shared by multiple contexts. Here are the rules:

1. Your application may access the object across multiple contexts simultaneously provided the object is not being modified.
2. While the object is being modified by commands sent to a context, the object must not be read or modified on any other context.
3. After an object has been modified, all contexts must rebind the object to see the changes. The contents of the object are undefined if a context references it before binding it.