Quoting Tvrtko Ursulin (2019-01-17 16:27:04)
>
> On 17/01/2019 14:34, Chris Wilson wrote:
> > Remove the struct_mutex requirement for looking up the vma for an
> > object.
>
> Another patch with missing change log.
>
> I see that you at least fixed the tree typo since the round I last
> reviewed. But I also had some other questions which I did not see you
> commented on.
>
> Anyways, it is very hard to review without change logs.. I am not sure
> why is this series particularly bad in this respect.
The short explanation, as given on the next patch,
rb = *p;
pos = rb_entry(rb, struct i915_vma, obj_node);
+ /*
+ * If the view already exists in the tree, another thread
+ * already created a matching vma, so return the older instance
+ * and dispose of ours.
+ */
cmp = i915_vma_compare(pos, vm, view);
if (cmp == 0) {
spin_unlock(&obj->vma.lock);
@@ -294,6 +299,7 @@ i915_vma_instance(struct drm_i915_gem_object *obj,
vma = vma_lookup(obj, vm, view);
spin_unlock(&obj->vma.lock);
+ /* vma_create() will resolve the race if another creates the vma */
if (unlikely(!vma))
vma = vma_create(obj, vm, view);
which should explain why the whitespace is peculiar and the early return
returns pos not vma.
-Chris
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