[Mesa-dev] [PATCH v3 0/4] Disable glthread if libX11 isn't thread-safe

[Gregory Hainaut]

On 5/8/17, Emil Velikov <emil.l.velikov at gmail.com> wrote:
> Having a look at Xlib might be good indeed.
>
> Then again, the solution you've proposed looks perfectly reasonable,
> IMHO. It handles the problem _now_ and should also work when/if we
> address Xlib.
> I'll take another look today/tomorrow, but I think the series is
> perfectly fine to land as-is.
>
> Thanks
> Emil

Hello Emil,

Yes you're right. And potentially it can be back-ported to stable
branch. Besides it would allow to know which applications aren't X
thread safe. And potentially app owners can fix the issue too.

By the way, I don't have commit access so feel free to push the series :)

On 5/8/17, Eric Anholt <eric at anholt.net> wrote:
> gregory hainaut <gregory.hainaut at gmail.com> writes:
>
>> On Fri, 5 May 2017 17:45:01 +0200
>> Axel Davy <axel.davy at normalesup.org> wrote:
>>
>>> Hi,
>>>
>>> There should be very few X11 calls while rendering (basically only at
>>> the beginning or end of a frame).
>>>
>>> Why not just always run these calls in the main thread (and wait for
>>> glthread work to finish) ?
>>>
>>> That's basically what we do for gallium nine.
>>>
>>> Yours,
>>>
>>> Axel
>>
>> Hello Axel,
>>
>> Yes it is another possibility. It would requires to track gl calls that
>> end up in X11.
>> I'm not sure if there is an easy way to list all those gl functions. There
>> are at least the
>> draw calls and maybe the clear operations. Besides I'm afraid that we will
>> need to handle
>> various corner cases of the OpenGL API. It is doable but likely more
>> complicated.
>
> General GL calls (draws, clears) won't call X11 except for DRI2's
> GetBuffers.  If you're in DRI3, I believe you won't need to worry about
> that at all.
>
> I think this patch is a good start, though.
>

Hello Eric,

Indeed I saw this behavior on Nouveau. I got a crash on
GetBuffersWithFormat on DRI2 but it was fine on DRI3. I still kept the
check on GLX/DRI3 because I don't know if we have a strong guarantee
that X11 is never used.

Cheers,
Gregory