Re: [Intel-gfx] [CI 6/6] drm/i915/gem: Drop lru bumping on display unpinning

[Dave Airlie <airlied@gmail.com>]

On Wed, 20 Jan 2021 at 07:43, Chris Wilson <chris@chris-wilson.co.uk> wrote:
>
> Simplify the frontbuffer unpin by removing the lock requirement. The LRU
> bumping was primarily to protect the GTT from being evicted and from
> frontbuffers being eagerly shrunk. Now we protect frontbuffers from the
> shrinker, and we avoid accidentally evicting from the GTT, so the
> benefit from bumping LRU is no more, and we can save more time by not.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Reviewed-by: Matthew Auld <matthew.auld@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c |  7 +--
>  drivers/gpu/drm/i915/display/intel_overlay.c |  4 +-
>  drivers/gpu/drm/i915/gem/i915_gem_domain.c   | 45 --------------------
>  drivers/gpu/drm/i915/gem/i915_gem_object.h   |  1 -
>  4 files changed, 4 insertions(+), 53 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 32ff9d201aeb..2bd04e631eaa 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -1430,7 +1430,7 @@ intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb,
>                  */
>                 ret = i915_vma_pin_fence(vma);
>                 if (ret != 0 && INTEL_GEN(dev_priv) < 4) {
> -                       i915_gem_object_unpin_from_display_plane(vma);
> +                       i915_vma_unpin(vma);
>                         vma = ERR_PTR(ret);
>                         goto err;
>                 }
> @@ -1448,12 +1448,9 @@ intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb,
>
>  void intel_unpin_fb_vma(struct i915_vma *vma, unsigned long flags)
>  {
> -       i915_gem_object_lock(vma->obj, NULL);
>         if (flags & PLANE_HAS_FENCE)
>                 i915_vma_unpin_fence(vma);
> -       i915_gem_object_unpin_from_display_plane(vma);
> -       i915_gem_object_unlock(vma->obj);
> -

Why does this drop the locking here without explanation and without
reviewer comments?

Any patches from Chris that touch locking need vastly more review than
rubberstamps.

Dave.
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