Quoting Chris Wilson (2019-03-21 08:05:32)
> If we are already in the desired write domain of a set-domain ioctl,
> then there is nothing for us to do and we can quickly return back to
> userspace, avoiding any lock contention.
>
> Secondary aspect of this is that we undo the arbitrary fetching and
> potential flushing of all pages for a set-domain(.write=CPU) call on a
> fresh object -- which was introduced simply because we do the get-pages
> before taking the struct_mutex.
>
> References: 40e62d5d6be8 ("drm/i915: Acquire the backing storage outside of struct_mutex in set-domain")
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> Cc: Matthew Auld <matthew.william.auld@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 1a684b7e8c09..e30165536f9a 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1484,7 +1484,8 @@ i915_gem_set_domain_ioctl(struct drm_device *dev, void *data,
> if ((write_domain | read_domains) & I915_GEM_GPU_DOMAINS)
> return -EINVAL;
>
> - /* Having something in the write domain implies it's in the read
> + /*
> + * Having something in the write domain implies it's in the read
> * domain, and only that read domain. Enforce that in the request.
> */
> if (write_domain != 0 && read_domains != write_domain)
> @@ -1494,7 +1495,14 @@ i915_gem_set_domain_ioctl(struct drm_device *dev, void *data,
> if (!obj)
> return -ENOENT;
>
> - /* Try to flush the object off the GPU without holding the lock.
> + /* Already in the desired target write domain? Nothing for us to! */
> + if (READ_ONCE(obj->write_domain) == write_domain) {
This should be write_domain && ...
-Chris
_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
