[Intel-gfx] [PATCH 1/3] drm/i915: Handle i915_active_fence_set() with the same fence

[Tvrtko Ursulin]

On 06/11/2019 15:48, Chris Wilson wrote:
> If the caller wants to overwrite the currently tracked fence, with
> itself, as far as the tracking is concerned it is a no-op, so simply
> allow it.

This is needed for some of the following patches in this series?

Regards,

Tvrtko

> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
>   drivers/gpu/drm/i915/i915_active.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
> index 207383dda84d..cde984744f20 100644
> --- a/drivers/gpu/drm/i915/i915_active.c
> +++ b/drivers/gpu/drm/i915/i915_active.c
> @@ -759,7 +759,9 @@ __i915_active_fence_set(struct i915_active_fence *active,
>   
>   	prev = rcu_dereference_protected(active->fence, active_is_held(active));
>   	if (prev) {
> -		GEM_BUG_ON(prev == fence);
> +		if (unlikely(prev == fence))
> +			goto unlock;
> +
>   		spin_lock_nested(prev->lock, SINGLE_DEPTH_NESTING);
>   		__list_del_entry(&active->cb.node);
>   		spin_unlock(prev->lock); /* serialise with prev->cb_list */
> @@ -781,6 +783,7 @@ __i915_active_fence_set(struct i915_active_fence *active,
>   	rcu_assign_pointer(active->fence, fence);
>   	list_add_tail(&active->cb.node, &fence->cb_list);
>   
> +unlock:
>   	spin_unlock_irqrestore(fence->lock, flags);
>   
>   	return prev;
>