On Fri, Jun 03, 2016 at 05:55:44PM +0100, Chris Wilson wrote:
> Since we are not concerned with userspace racing itself with set-tiling
> (the order is indeterminant even if we take a lock), then we can safely
> read back the single obj->tiling_mode and do the static lookup of
> swizzle mode without having to take a lock.
>
> get-tiling is reasonably frequent due to the back-channel passing around
> of tiling parameters in DRI2/DRI3.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem_tiling.c | 8 ++------
> 1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
> index 326de7eae101..d6acd0a27c06 100644
> --- a/drivers/gpu/drm/i915/i915_gem_tiling.c
> +++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
> @@ -302,10 +302,8 @@ i915_gem_get_tiling(struct drm_device *dev, void *data,
> if (!obj)
> return -ENOENT;
>
> - mutex_lock(&dev->struct_mutex);
> -
> args->tiling_mode = obj->tiling_mode;
READ_ONCE here. With that Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> - switch (obj->tiling_mode) {
> + switch (args->tiling_mode) {
> case I915_TILING_X:
> args->swizzle_mode = dev_priv->mm.bit_6_swizzle_x;
> break;
> @@ -329,8 +327,6 @@ i915_gem_get_tiling(struct drm_device *dev, void *data,
> if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_10_17)
> args->swizzle_mode = I915_BIT_6_SWIZZLE_9_10;
>
> - i915_gem_object_put(obj);
> - mutex_unlock(&dev->struct_mutex);
> -
> + i915_gem_object_put_unlocked(obj);
> return 0;
> }
> --
> 2.8.1
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
