Re: [PATCH V2] accel/amdxdna: Fix unexpected wait when flushing notifier_wq

[Max Zhen]

On 8/13/2026 Thu 13:50, Lizhi Hou wrote:

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....@amd.com>

Reviewed-by: Max Zhen <max.z...@amd.com>

---
V2:
   Fix sashiko comment.

  drivers/accel/amdxdna/amdxdna_gem.c | 69 +++++++++++++++++++----------
  drivers/accel/amdxdna/amdxdna_gem.h |  1 +
  2 files changed, 47 insertions(+), 23 deletions(-)

diff --git a/drivers/accel/amdxdna/amdxdna_gem.c 
b/drivers/accel/amdxdna/amdxdna_gem.c
index 1c63eff0a4a8..1c17122d1327 100644
--- a/drivers/accel/amdxdna/amdxdna_gem.c
+++ b/drivers/accel/amdxdna/amdxdna_gem.c
@@ -253,13 +253,16 @@ static bool amdxdna_hmm_invalidate(struct 
mmu_interval_notifier *mni,
        struct amdxdna_gem_obj *abo = mapp->abo;
        struct amdxdna_dev *xdna;

+ if (!mmu_notifier_range_blockable(range))

+               return false;
+
+       if (mapp->unmapped)
+               return true;
+
        xdna = to_xdna_dev(to_gobj(abo)->dev);
        XDNA_DBG(xdna, "Invalidating range 0x%lx, 0x%lx, type %d",
                 mapp->range.start, mapp->range.end, abo->type);

- if (!mmu_notifier_range_blockable(range))

-               return false;
-
        down_write(&xdna->notifier_lock);
        abo->mem.map_invalid = true;
        mapp->invalid = true;
@@ -301,33 +304,40 @@ 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 +351,20 @@ 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 +667,7 @@ 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 {