[Mesa-dev] [PATCH] llvmpipe: Always return some fence in flush (v2)

[Tomasz Figa]

On Sun, Dec 23, 2018 at 12:55 AM Roland Scheidegger <sroland at vmware.com> wrote:
>
> Alright, I guess it should work...
>
> Reviewed-by: Roland Scheidegger <sroland at vmware.com>
>

Thanks!

Would we have anyone who could help to commit it?

(I know that I was supposed to apply for commit rights, but I expect
my contribution rate to be relatively low, due to a shift to different
areas, so I don't think I'm a good candidate for a committer anymore.)

Best regards,
Tomasz

>
> Am 14.12.18 um 09:17 schrieb Tomasz Figa:
> > If there is no last fence, due to no rendering happening yet, just
> > create a new signaled fence and return it, to match the expectations of
> > the EGL sync fence API.
> >
> > Fixes random "Could not create sync fence 0x3003" assertion failures from
> > Skia on Android, coming from the following code:
> >
> > https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fandroid.googlesource.com%2Fplatform%2Fframeworks%2Fbase%2F%2B%2Fmaster%2Flibs%2Fhwui%2Fpipeline%2Fskia%2FSkiaOpenGLPipeline.cpp%23427&data=02%7C01%7Csroland%40vmware.com%7Cbbfaf154367d449a153608d6619ca298%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C0%7C636803722709844114&sdata=Jau0msKOhAhDMMklBWCtuse40%2FMxpLR50vqjtiyVBYw%3D&reserved=0
> >
> > Reproducible especially with thread count >= 4.
> >
> > One could make the driver always keep the reference to the last fence,
> > but:
> >
> >  - the driver seems to explicitly destroy the fence whenever a rendering
> >    pass completes and changing that would require a significant functional
> >    change to the code. (Specifically, in lp_scene_end_rasterization().)
> >
> >  - it still wouldn't solve the problem of an EGL sync fence being created
> >    and waited on without any rendering happening at all, which is
> >    also likely to happen with Android code pointed to in the commit.
> >
> > Therefore, the simple approach of always creating a fence is taken,
> > similarly to other drivers, such as radeonsi.
> >
> > Tested with piglit llvmpipe suite with no regressions and following
> > tests fixed:
> >
> > egl_khr_fence_sync
> >  conformance
> >   eglclientwaitsynckhr_flag_sync_flush
> >   eglclientwaitsynckhr_nonzero_timeout
> >   eglclientwaitsynckhr_zero_timeout
> >   eglcreatesynckhr_default_attributes
> >   eglgetsyncattribkhr_invalid_attrib
> >   eglgetsyncattribkhr_sync_status
> >
> > v2:
> >  - remove the useless lp_fence_reference() dance (Nicolai),
> >  - explain why creating the dummy fence is the right approach.
> >
> > Signed-off-by: Tomasz Figa <tfiga at chromium.org>
> > ---
> >  src/gallium/drivers/llvmpipe/lp_setup.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/src/gallium/drivers/llvmpipe/lp_setup.c b/src/gallium/drivers/llvmpipe/lp_setup.c
> > index b087369473..e72e119c8a 100644
> > --- a/src/gallium/drivers/llvmpipe/lp_setup.c
> > +++ b/src/gallium/drivers/llvmpipe/lp_setup.c
> > @@ -361,6 +361,8 @@ lp_setup_flush( struct lp_setup_context *setup,
> >
> >     if (fence) {
> >        lp_fence_reference((struct lp_fence **)fence, setup->last_fence);
> > +      if (!*fence)
> > +         *fence = (struct pipe_fence_handle *)lp_fence_create(0);
> >     }
> >  }
> >
> >
>