[Mesa-dev] [PATCH 7/9] anv: Implement VK_KHX_external_semaphore_fd

[Jason Ekstrand]

On Tue, Feb 28, 2017 at 9:14 AM, Chris Wilson <chris at chris-wilson.co.uk>
wrote:

> On Tue, Feb 28, 2017 at 08:56:45AM -0800, Jason Ekstrand wrote:
> > This implementation allocates a 4k BO for each semaphore that can be
> > exported using OPAQUE_FD and uses the kernel's already-existing
> > synchronization mechanism on BOs.
> > ---
> >  VkResult
> >  anv_cmd_buffer_execbuf(struct anv_device *device,
> > -                       struct anv_cmd_buffer *cmd_buffer)
> > +                       struct anv_cmd_buffer *cmd_buffer,
> > +                       const VkSemaphore *in_semaphores,
> > +                       uint32_t num_in_semaphores,
> > +                       const VkSemaphore *out_semaphores,
> > +                       uint32_t num_out_semaphores)
> >  {
> >     struct anv_execbuf execbuf;
> >     anv_execbuf_init(&execbuf);
> >
> > +   for (uint32_t i = 0; i < num_in_semaphores; i++) {
> > +      ANV_FROM_HANDLE(anv_semaphore, semaphore, in_semaphores[i]);
> > +      assert(semaphore->temporary.type == ANV_SEMAPHORE_TYPE_NONE);
> > +      struct anv_semaphore_impl *impl = &semaphore->permanent;
> > +
> > +      switch (impl->type) {
> > +      case ANV_SEMAPHORE_TYPE_BO:
> > +         anv_execbuf_add_bo(&execbuf, &impl->bo, NULL, 0,
> &device->alloc);
> > +         break;
> > +      default:
> > +         break;
> > +      }
> > +   }
>
> Do the in/out semaphores[] have any constraints against repeated use? If
> you pass in the same handle twice into the execbuf, it will EINVAL.
> (Both within the in/out arrays and between them.)
>

Yes.  The way Vulkan defines the wait/signaling semantics, you can't use
the same semaphore twice in a command buffer submission


> Or does execbuf_add_bo do a repeated use check?
>

Yes it does.  Well, mostly.  There appear to still be a few issues there
thanks to no longer having a direct GEM BO -> anv_bo mapping which need to
be sorted out.


> > +   for (uint32_t i = 0; i < num_out_semaphores; i++) {
> > +      ANV_FROM_HANDLE(anv_semaphore, semaphore, out_semaphores[i]);
> > +      assert(semaphore->temporary.type == ANV_SEMAPHORE_TYPE_NONE);
> > +      struct anv_semaphore_impl *impl = &semaphore->permanent;
> > +
> > +      switch (impl->type) {
> > +      case ANV_SEMAPHORE_TYPE_BO:
> > +         anv_execbuf_add_bo(&execbuf, &impl->bo, NULL,
> EXEC_OBJECT_WRITE,
> > +                            &device->alloc);
> > +         break;
> > +      default:
> > +         break;
> > +      }
> > +   }
>
> Seperate in/out arrays curtains the issues I could see with the implicit
> fences accidentally serialising input-only semaphores.
> -Chris
>
> --
> Chris Wilson, Intel Open Source Technology Centre
>
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