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

[Roland Scheidegger]

Alright, I guess it should work...

Reviewed-by: Roland Scheidegger <sroland at vmware.com>


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);
>     }
>  }
>  
>