[Mesa-dev] glXMakeCurrent crashes (was: Re: How to obtain OpenGL implementation/driver information?)
tfogal at sci.utah.edu
Fri Feb 4 13:57:49 PST 2011
Benoit Jacob wrote:
> ----- Original Message -----
>> On Thu, Feb 3, 2011 at 4:37 PM, Benoit Jacob <bjacob at mozilla.com>
>>> I'm trying to see how to implement selective
>>> whitelisting/blacklisting of driver versions on X11 (my use case is
>>> to whitelist drivers for Firefox). The naive approach consists in
>>> creating an OpenGL context and calling glGetString(), however that
>>> is not optimal for me, for these reasons:
>>> * This has been enough to trigger crashes in the past.
>>> Ideally I want to be able to know the driver name, driver version,
>>> Mesa version, and any other thing that you think may be relevant. I
>>> need to get that information in a fast and safe way.
>> There is no other way than glGetString if you ever experienced crash
>> with it, it would be because you are doing something terribly wrong
>> like using it without current context.
> It's not glGetString that's crashing, it's glXMakeCurrent.
> I forwarded a bug report from a user, though he's not been able to reproduce since:
> A search in Mesa's bugzilla confirms that I'm not alone:
This latter bug looks like an i915 driver bug, as opposed to a
> Since the glGetString way will at best be slow, especially if we have
> to XSync and check for errors, could you consider exposing this
> information as new glXGetServerString / glXGetClientString strings?
? I don't understand the logic here.
You're hitting a bug in glXCreateContext or MakeCurrent or something
like that. So you'd like to add an entire new way to query the same
information a driver already provides, just to provide an alternate path
that hopefully doesn't exhibit the bug?
Just fix the bug! There's no reason for glX extensions to add new
> It seems that such crashes happen only after a X error in glxCreateNewContext. So it may be possible to avoid them by doing XSync and checking for errors. But that makes the process even slower.
I don't think you need to XSync. Just do:
in your code. If that crashes, there's a bug in the implementation, so
report it and let's get it fixed!
There's really not much of a reason for MakeCurrent anyway, because most
applications do not have a need for multiple contexts, or if they do
they only need them in separate threads.
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