[PATCH V1] accel/amdxdna: Fix unexpected wait when flushing notifier_wq

[Lizhi Hou]

In amdxdna_gem_obj_free(), flush_workqueue(xdna->notifier_wq) waits for
all pending work items on the device-global notifier workqueue, rather
than only the work items associated with the BO being freed.

If another BO has a pending hmm_unreg_work, freeing an unrelated BO can
be unnecessarily blocked until that work completes.

mmu_interval_notifier_remove() is deferred to a workqueue because it
cannot be called from the MMU notifier callback itself. The BO free path
is not a notifier callback, so call mmu_interval_notifier_remove()
directly there and avoid the workqueue.

Fixes: e486147c912f ("accel/amdxdna: Add BO import and export")
Signed-off-by: Lizhi Hou <lizhi.hou@xxxxxxx>
---
 drivers/accel/amdxdna/amdxdna_gem.c | 60 +++++++++++++++++++----------
 drivers/accel/amdxdna/amdxdna_gem.h |  1 +
 2 files changed, 41 insertions(+), 20 deletions(-)

diff --git a/drivers/accel/amdxdna/amdxdna_gem.c b/drivers/accel/amdxdna/amdxdna_gem.c
index 1c63eff0a4a8..d6aa862e2d5b 100644
--- a/drivers/accel/amdxdna/amdxdna_gem.c
+++ b/drivers/accel/amdxdna/amdxdna_gem.c
@@ -301,33 +301,40 @@ static void amdxdna_hmm_unregister(struct amdxdna_gem_obj *abo,
 
 	down_write(&xdna->notifier_lock);
 	list_for_each_entry(mapp, &abo->mem.umap_list, node) {
-		if (!vma || compare_range(mapp, vma->vm_mm, vma->vm_start, vma->vm_end)) {
-			if (!mapp->unmapped) {
-				queue_work(xdna->notifier_wq, &mapp->hmm_unreg_work);
-				mapp->unmapped = true;
-			}
-			if (vma)
-				break;
-		}
+		if (!compare_range(mapp, vma->vm_mm, vma->vm_start, vma->vm_end))
+			continue;
+
+		queue_work(xdna->notifier_wq, &mapp->hmm_unreg_work);
+		mapp->unmapped = true;
 	}
 	up_write(&xdna->notifier_lock);
 }
 
-static void amdxdna_umap_release(struct kref *ref)
+static void amdxdna_hmm_unregister_all(struct amdxdna_gem_obj *abo)
 {
-	struct amdxdna_umap *mapp = container_of(ref, struct amdxdna_umap, refcnt);
-	struct amdxdna_gem_obj *abo = mapp->abo;
-	struct amdxdna_dev *xdna;
-
-	mmu_interval_notifier_remove(&mapp->notifier);
+	struct amdxdna_dev *xdna = to_xdna_dev(to_gobj(abo)->dev);
+	struct amdxdna_umap *mapp, *tmp;
+	LIST_HEAD(dead);
 
-	xdna = to_xdna_dev(to_gobj(mapp->abo)->dev);
 	down_write(&xdna->notifier_lock);
-	list_del(&mapp->node);
-	if (list_empty(&abo->mem.umap_list))
-		abo->mem.uva = AMDXDNA_INVALID_ADDR;
+	list_for_each_entry_safe(mapp, tmp, &abo->mem.umap_list, node) {
+		mapp->unmapped = true;
+		mapp->cleanup = true;
+		list_move(&mapp->node, &dead);
+	}
 	up_write(&xdna->notifier_lock);
 
+	list_for_each_entry_safe(mapp, tmp, &dead, node) {
+		cancel_work_sync(&mapp->hmm_unreg_work);
+		amdxdna_umap_put(mapp);
+	}
+}
+
+static void amdxdna_umap_release(struct kref *ref)
+{
+	struct amdxdna_umap *mapp = container_of(ref, struct amdxdna_umap, refcnt);
+
+	mmu_interval_notifier_remove(&mapp->notifier);
 	kvfree(mapp->range.hmm_pfns);
 	kfree(mapp);
 }
@@ -341,6 +348,20 @@ static void amdxdna_hmm_unreg_work(struct work_struct *work)
 {
 	struct amdxdna_umap *mapp = container_of(work, struct amdxdna_umap,
 						 hmm_unreg_work);
+	struct amdxdna_gem_obj *abo = mapp->abo;
+	struct amdxdna_dev *xdna;
+
+	xdna = to_xdna_dev(to_gobj(mapp->abo)->dev);
+	down_write(&xdna->notifier_lock);
+	if (mapp->cleanup) {
+		up_write(&xdna->notifier_lock);
+		return;
+	}
+
+	list_del(&mapp->node);
+	if (list_empty(&abo->mem.umap_list))
+		abo->mem.uva = AMDXDNA_INVALID_ADDR;
+	up_write(&xdna->notifier_lock);
 
 	amdxdna_umap_put(mapp);
 }
@@ -643,8 +664,7 @@ static void amdxdna_gem_obj_free(struct drm_gem_object *gobj)
 	struct amdxdna_dev *xdna = to_xdna_dev(gobj->dev);
 	struct amdxdna_gem_obj *abo = to_xdna_obj(gobj);
 
-	amdxdna_hmm_unregister(abo, NULL);
-	flush_workqueue(xdna->notifier_wq);
+	amdxdna_hmm_unregister_all(abo);
 
 	if (abo->pinned)
 		amdxdna_gem_unpin(abo);
diff --git a/drivers/accel/amdxdna/amdxdna_gem.h b/drivers/accel/amdxdna/amdxdna_gem.h
index 1e90e32bf3cd..fb033ced1045 100644
--- a/drivers/accel/amdxdna/amdxdna_gem.h
+++ b/drivers/accel/amdxdna/amdxdna_gem.h
@@ -20,6 +20,7 @@ struct amdxdna_umap {
 	struct kref			refcnt;
 	bool				invalid;
 	bool				unmapped;
+	bool				cleanup;
 };
 
 struct amdxdna_mem {
-- 
2.34.1