Threading with bitmap datas converted to textures silent crashes the game

[SomeGuyWhoLovesCoding]

Describe the bug
So, someone helped me with how I would reduce memory usage when loading an image by converting it to a texture, simply with this function:

public static function toTexture(source:BitmapData):BitmapData
{
	if (source.readable && !GL.isContextLost())
	{
		var context:Context3D = Lib.current.stage.context3D;
		var texture:TextureBase = source.getTexture(context);
		return source = BitmapData.fromTexture(texture);
	}

	return source;
}

(All the classes were imported for this btw)
And then, when I tried it out while also threading, it silent crashes the game. I was so shocked that it happened. I did make the thread handler function safer by adding a mutex which acquires before the call, and releases the mutex after that.

OpenFL and Lime versions: Latest

To Reproduce
Steps to reproduce the behavior:

1. Basically add this:

// Add this
import lime.graphics.Image;
import openfl.display.BitmapData;

class Main extends openfl.display.Sprite
{
    public function new():Void
    {
        super();
        new sys.thread.FixedThreadPool(1).run(function()
        {
            var img:Image = toTexture(Image.fromBitmapData(BitmapData.fromFile('image.png')));
        });
    }

    // See "Describe the bug" for the function
}

2. Test it out

Expected behavior
I wanted the bitmap data to successfully convert to a texture (toTexture function) while also using threading (sys.thread.FixedThreadPool), and I expected the texture to not crash the game.

Screenshots
[No screenshot available, just a silent game crash]

OpenFL Targets
Windows (Tested), any other target (Not tested).

Additional context
N/A

[joshtynjala]

As I understand it, all Stage 3D code is required to remain in the main thread (and that is not considered a bug). You can use threads for other things, though.

[barisyild]

toTexture method costs almost nothing, for thread-safety you should run this method in the main thread.
OpenGL is single thread supported, so you can't make gl calls in another thread.