[1/3] drm/i915: Handle i915_active_fence_set() with the same fence
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Message ID 20191106154810.5843-1-chris@chris-wilson.co.uk
State New
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Series
  • [1/3] drm/i915: Handle i915_active_fence_set() with the same fence
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Commit Message

Chris Wilson Nov. 6, 2019, 3:48 p.m. UTC
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.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/i915_active.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Tvrtko Ursulin Nov. 8, 2019, 10:37 a.m. UTC | #1
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@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@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;
>
Chris Wilson Nov. 8, 2019, 10:42 a.m. UTC | #2
Quoting Tvrtko Ursulin (2019-11-08 10:37:37)
> 
> 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?

The implementation is relaxed in patch 3, which means we allow the user
to update the same i915_request.fence on the same timeline multiple times.
We already allow them to use the same fence multiple times, symmetry is
good?...
-Chris

Patch
diff mbox series

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;