[Mesa-dev] [PATCH v3 07/18] anv/allocator: Add a BO cache

[Chad Versace]

On Wed 15 Mar 2017, Jason Ekstrand wrote:
> This cache allows us to easily ensure that we have a unique anv_bo for
> each gem handle.  We'll need this in order to support multiple-import of
> memory objects and semaphores.
> 
> v2 (Jason Ekstrand):
>  - Reject BO imports if the size doesn't match the prime fd size as
>    reported by lseek().
> 
> v3 (Jason Ekstrand):
>  - Fix reference counting around cache_release (Chris Willson)
>  - Move the mutex_unlock() later in cache_release
> ---
>  src/intel/vulkan/anv_allocator.c | 261 +++++++++++++++++++++++++++++++++++++++
>  src/intel/vulkan/anv_private.h   |  26 ++++
>  2 files changed, 287 insertions(+)



> +VkResult anv_bo_cache_alloc(struct anv_device *device,
> +                            struct anv_bo_cache *cache,
> +                            uint64_t size, struct anv_bo **bo,
> +                            VkAllocationCallbacks *alloc);

> +VkResult anv_bo_cache_import(struct anv_device *device,
> +                             struct anv_bo_cache *cache,
> +                             int fd, uint64_t size, struct anv_bo **bo,
> +                             VkAllocationCallbacks *alloc);

> +void anv_bo_cache_release(struct anv_device *device,
> +                          struct anv_bo_cache *cache,
> +                          struct anv_bo *bo,
> +                          VkAllocationCallbacks *alloc);
> +

The app may do this:

  // fd1 != fd2
  // fd1 and fd2 wrap the same gem handle

  mem1 = vkAllocateMemory(import fd1, pAllocator=alloc1); // anv_cached_bo is allocated here
  mem2 = vkAllocateMemory(import fd2, pAllocator=alloc2);

  ...

  vkFreeMemory(mem1, alloc1);
  vkFreeMemory(mem2, alloc2); // anv_cached_bo is freed here

So we can't use either pAllocator to allocate/free the anv_cached_bo,
unless anv_cached_bo also cached its original allocator.
If we don't cache the allocator (and please, let's not), then the
'alloc' params to anv_bo_cache_alloc/import/release are dead params.
We must use an allocator that is not bound
to the anv_cached_bo, such as device->alloc.


Patch 8/18 correctly passes device->alloc into these functions. But,
since the 'alloc' params aren't really used, they should be dropped to
prevent accidental misuse.