[Intel-gfx] [RFC 10/10] drm/i915/vm_bind: Fix vm->vm_bind_mutex and vm->mutex nesting

[Niranjana Vishwanathapura]

VM_BIND functionality maintain that vm->vm_bind_mutex will never be taken
while holding vm->mutex.
However, while closing 'vm', vma is destroyed while holding vm->mutex.
But vma releasing needs to take vm->vm_bind_mutex in order to delete vma
from the vm_bind_list. To avoid this, destroy the vma outside vm->mutex
while closing the 'vm'.

Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathap...@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_gtt.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.c 
b/drivers/gpu/drm/i915/gt/intel_gtt.c
index 4ab3bda644ff..4f707d0eb3ef 100644
--- a/drivers/gpu/drm/i915/gt/intel_gtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gtt.c
@@ -109,7 +109,8 @@ int map_pt_dma_locked(struct i915_address_space *vm, struct 
drm_i915_gem_object
        return 0;
 }
 
-static void clear_vm_list(struct list_head *list)
+static void clear_vm_list(struct list_head *list,
+                         struct list_head *destroy_list)
 {
        struct i915_vma *vma, *vn;
 
@@ -138,8 +139,7 @@ static void clear_vm_list(struct list_head *list)
                        i915_vm_resv_get(vma->vm);
                        vma->vm_ddestroy = true;
                } else {
-                       i915_vma_destroy_locked(vma);
-                       i915_gem_object_put(obj);
+                       list_move_tail(&vma->vm_link, destroy_list);
                }
 
        }
@@ -147,16 +147,29 @@ static void clear_vm_list(struct list_head *list)
 
 static void __i915_vm_close(struct i915_address_space *vm)
 {
+       struct i915_vma *vma, *vn;
+       struct list_head list;
+
+       INIT_LIST_HEAD(&list);
+
        mutex_lock(&vm->mutex);
 
-       clear_vm_list(&vm->bound_list);
-       clear_vm_list(&vm->unbound_list);
+       clear_vm_list(&vm->bound_list, &list);
+       clear_vm_list(&vm->unbound_list, &list);
 
        /* Check for must-fix unanticipated side-effects */
        GEM_BUG_ON(!list_empty(&vm->bound_list));
        GEM_BUG_ON(!list_empty(&vm->unbound_list));
 
        mutex_unlock(&vm->mutex);
+
+       /* Destroy vmas outside vm->mutex */
+       list_for_each_entry_safe(vma, vn, &list, vm_link) {
+               struct drm_i915_gem_object *obj = vma->obj;
+
+               i915_vma_destroy(vma);
+               i915_gem_object_put(obj);
+       }
 }
 
 /* lock the vm into the current ww, if we lock one, we lock all */
-- 
2.21.0.rc0.32.g243a4c7e27