Bug 74143

bisected to following commit, it looks like commit breaks the case as there is no more checking for the BUFFER_BACK_LEFT renderbuffer which does not exist.

--- 8< ---
commit 11baad35088dfd4bdabc1710df650dbfb413e7a3
Author: Kristian Høgsberg <krh@bitplanet.net>
Date:   Tue Jan 21 12:17:03 2014 -0800

    intel: Fix initial MakeCurrent for single-buffer drawables

Created attachment 93282 [details] [review]
patch to fix the issue

Kristian, could you review the changes?

Created attachment 93487 [details] [review]
Fix for GLX makecurrent with None drawable/readable.

That's not the right fix and this was never working right except by accident.  The attached patch is what we want.  I'll send it to mesa-dev for review.

Adding irc discussion with Ian here:

12:15 < idr> krh: In the None drawable case, both read and draw must be None.  
             Is that checked somewhere?
...
12:29 < krh> idr: seems like something we should do in MakeContextCurrent, but 
             I don't see it there
12:30 < krh> idr: if only one of them is NULL, the dri driver will crash
12:30 < idr> I'm also not sure how we'll enforce the "...and the OpenGL version 
             supported by <ctx> is 3.0 or greater." requirement. :(
12:30 < idr> Now or with your patch?
12:31 < krh> without my patch, the driver would never see a NULL draw/readable
12:32 < krh> so it wouldn't hit that case

I think further checking and validation of the extension makes sense, but it's orthogonal to fixing this regression.  Once change in behavior is that without the patch in comment 4, passing a None and a non-None drawable to glxMakeContext Current I get

X Error of failed request:  BadDrawable (invalid Pixmap or Window parameter)
  Major opcode of failed request:  152 (DRI2)
  Minor opcode of failed request:  3 (DRI2CreateDrawable)
  Resource id in failed request:  0x0
  Serial number of failed request:  35
  Current serial number in output stream:  37

with the patch we segfault instead.

So more work is needed to better check input, but that's not a new problem.  Unless Ian objects, I'll commit this tomorrow.

Committed to master:

commit f658150639c36eda351590e757247c56507f494f
Author: Kristian Høgsberg <krh@bitplanet.net>
Date:   Wed Feb 5 11:43:58 2014 -0800

    glx: Pass NULL DRI drawables into the DRI driver for None GLX drawables
    
    GLX_ARB_create_context allows making a GLX context current with None
    drawable and readables, but this was never implemented correctly in GLX.
    We would create a __DRIdrawable for the None GLX drawable and pass that
    to the DRI driver and that would somehow work.  Now it's somehow broken.
    
    The way this should have worked is that we pass a NULL DRI drawable
    to the DRI driver when the GLX user calls glXMakeContextCurrent()
    with None for drawable and readables.
    
    https://bugs.freedesktop.org/show_bug.cgi?id=74143
    Signed-off-by: Kristian Høgsberg <krh@bitplanet.net>

Verified.Fixed.