[Mesa-dev] [PATCH] dri2: add code to flush function of DRI2_Flush extension

[Alan Hourihane]

On 08/16/11 10:05, Michel Dänzer wrote:
> On Die, 2011-08-16 at 16:55 +0800, Cooper Yuan wrote:
>> We still call flush method of DRI2_Flush extension in other functions
>> of egl_dri2 driver. for example, dri2_copy_buffers(), because we
>> expect all the rendering to this drawable have been flushed before
>> copying the buffers.
>>
>>
>> The code I added eventually invokes st->pipe->flush(), so I think it
>> handles correctly, any concern?
> The more I look at the patch, the more I'm convinced it's wrong.
>
> At least with GLX, there's no requirement for the drawable to have any
> current context at SwapBuffers time. AFAICT this code will crash with a
> null pointer dereference in that case.
>
> I really suspect the problem you were trying to address with this needs
> to be addressed in EGL code. BTW, to get the same semantics as glFinish,
> the flush would need to be called with a non-NULL last argument and the
> returned fence waited for. 

Actually, I think it's right, but just needs to check for a valid context
first and do nothing if there isn't one.

This matches the semantics of dri2_glx.c

Alan.