drm/amdgpu: remove the userptr rmn->lock

Avoid a lock inversion problem by just using the mmap_sem to
protect the entries of the intervall tree.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>

1 files changed, 12 insertions, 20 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
index d4e2780c0796..61f0e3c3172a 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
@@ -48,8 +48,7 @@ struct amdgpu_mn {
         /* protected by adev->mn_lock */
         struct hlist_node       node;
 
-        /* objects protected by lock */
-        struct mutex            lock;
+        /* objects protected by mm->mmap_sem */
         struct rb_root          objects;
 };
 
@@ -72,8 +71,8 @@ static void amdgpu_mn_destroy(struct work_struct *work)
         struct amdgpu_mn_node *node, *next_node;
         struct amdgpu_bo *bo, *next_bo;
 
+        down_write(&rmn->mm->mmap_sem);
         mutex_lock(&adev->mn_lock);
-        mutex_lock(&rmn->lock);
         hash_del(&rmn->node);
         rbtree_postorder_for_each_entry_safe(node, next_node, &rmn->objects,
                                              it.rb) {
@@ -85,8 +84,8 @@ static void amdgpu_mn_destroy(struct work_struct *work)
                 }
                 kfree(node);
         }
-        mutex_unlock(&rmn->lock);
         mutex_unlock(&adev->mn_lock);
+        up_write(&rmn->mm->mmap_sem);
         mmu_notifier_unregister(&rmn->mn, rmn->mm);
         kfree(rmn);
 }
@@ -129,8 +128,6 @@ static void amdgpu_mn_invalidate_range_start(struct mmu_notifier *mn,
         /* notification is exclusive, but interval is inclusive */
         end -= 1;
 
-        mutex_lock(&rmn->lock);
-
         it = interval_tree_iter_first(&rmn->objects, start, end);
         while (it) {
                 struct amdgpu_mn_node *node;
@@ -165,8 +162,6 @@ static void amdgpu_mn_invalidate_range_start(struct mmu_notifier *mn,
                         amdgpu_bo_unreserve(bo);
                 }
         }
-
-        mutex_unlock(&rmn->lock);
 }
 
 static const struct mmu_notifier_ops amdgpu_mn_ops = {
@@ -203,7 +198,6 @@ static struct amdgpu_mn *amdgpu_mn_get(struct amdgpu_device *adev)
         rmn->adev = adev;
         rmn->mm = mm;
         rmn->mn.ops = &amdgpu_mn_ops;
-        mutex_init(&rmn->lock);
         rmn->objects = RB_ROOT;
 
         r = __mmu_notifier_register(&rmn->mn, mm);
@@ -250,7 +244,7 @@ int amdgpu_mn_register(struct amdgpu_bo *bo, unsigned long addr)
 
         INIT_LIST_HEAD(&bos);
 
-        mutex_lock(&rmn->lock);
+        down_write(&rmn->mm->mmap_sem);
 
         while ((it = interval_tree_iter_first(&rmn->objects, addr, end))) {
                 kfree(node);
@@ -264,7 +258,7 @@ int amdgpu_mn_register(struct amdgpu_bo *bo, unsigned long addr)
         if (!node) {
                 node = kmalloc(sizeof(struct amdgpu_mn_node), GFP_KERNEL);
                 if (!node) {
-                        mutex_unlock(&rmn->lock);
+                        up_write(&rmn->mm->mmap_sem);
                         return -ENOMEM;
                 }
         }
@@ -279,7 +273,7 @@ int amdgpu_mn_register(struct amdgpu_bo *bo, unsigned long addr)
 
         interval_tree_insert(&node->it, &rmn->objects);
 
-        mutex_unlock(&rmn->lock);
+        up_write(&rmn->mm->mmap_sem);
 
         return 0;
 }
@@ -294,17 +288,15 @@ int amdgpu_mn_register(struct amdgpu_bo *bo, unsigned long addr)
 void amdgpu_mn_unregister(struct amdgpu_bo *bo)
 {
         struct amdgpu_device *adev = bo->adev;
-        struct amdgpu_mn *rmn;
+        struct amdgpu_mn *rmn = bo->mn;
         struct list_head *head;
 
-        mutex_lock(&adev->mn_lock);
-        rmn = bo->mn;
-        if (rmn == NULL) {
-                mutex_unlock(&adev->mn_lock);
+        if (rmn == NULL)
                 return;
-        }
 
-        mutex_lock(&rmn->lock);
+        down_write(&rmn->mm->mmap_sem);
+        mutex_lock(&adev->mn_lock);
+
         /* save the next list entry for later */
         head = bo->mn_list.next;
 
@@ -318,6 +310,6 @@ void amdgpu_mn_unregister(struct amdgpu_bo *bo)
                 kfree(node);
         }
 
-        mutex_unlock(&rmn->lock);
         mutex_unlock(&adev->mn_lock);
+        up_write(&rmn->mm->mmap_sem);
 }