On Fri 22-06-18 16:36:49, Chris Wilson wrote:
Quoting Michal Hocko (2018-06-22 16:02:42)
Hi, this is an RFC and not tested at all. I am not very familiar with the mmu notifiers semantics very much so this is a crude attempt to achieve what I need basically. It might be completely wrong but I would like to discuss what would be a better way if that is the case.
get_maintainers gave me quite large list of people to CC so I had to trim it down. If you think I have forgot somebody, please let me know
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c index 854bd51b9478..5285df9331fa 100644 --- a/drivers/gpu/drm/i915/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/i915_gem_userptr.c @@ -112,10 +112,11 @@ static void del_object(struct i915_mmu_object *mo) mo->attached = false; }
-static void i915_gem_userptr_mn_invalidate_range_start(struct mmu_notifier *_mn, +static int i915_gem_userptr_mn_invalidate_range_start(struct mmu_notifier *_mn, struct mm_struct *mm, unsigned long start,
unsigned long end)
unsigned long end,bool blockable){ struct i915_mmu_notifier *mn = container_of(_mn, struct i915_mmu_notifier, mn); @@ -124,7 +125,7 @@ static void i915_gem_userptr_mn_invalidate_range_start(struct mmu_notifier *_mn, LIST_HEAD(cancelled);
if (RB_EMPTY_ROOT(&mn->objects.rb_root))
return;
return 0;The principle wait here is for the HW (even after fixing all the locks to be not so coarse, we still have to wait for the HW to finish its access).
Is this wait bound or it can take basically arbitrary amount of time?
The first pass would be then to not do anything here if !blockable.
something like this? (incremental diff)
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c index 5285df9331fa..e9ed0d2cfabc 100644 --- a/drivers/gpu/drm/i915/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/i915_gem_userptr.c @@ -122,6 +122,7 @@ static int i915_gem_userptr_mn_invalidate_range_start(struct mmu_notifier *_mn, container_of(_mn, struct i915_mmu_notifier, mn); struct i915_mmu_object *mo; struct interval_tree_node *it; + int ret = 0; LIST_HEAD(cancelled);
if (RB_EMPTY_ROOT(&mn->objects.rb_root)) @@ -133,6 +134,10 @@ static int i915_gem_userptr_mn_invalidate_range_start(struct mmu_notifier *_mn, spin_lock(&mn->lock); it = interval_tree_iter_first(&mn->objects, start, end); while (it) { + if (!blockable) { + ret = -EAGAIN; + goto out_unlock; + } /* The mmu_object is released late when destroying the * GEM object so it is entirely possible to gain a * reference on an object in the process of being freed @@ -154,8 +159,10 @@ static int i915_gem_userptr_mn_invalidate_range_start(struct mmu_notifier *_mn, spin_unlock(&mn->lock);
/* TODO: can we skip waiting here? */ - if (!list_empty(&cancelled) && blockable) + if (!list_empty(&cancelled)) flush_workqueue(mn->wq); + + return ret; }
static const struct mmu_notifier_ops i915_gem_userptr_notifier = {